Search

Furosemide (FUR), banned in sports events by the World Anti-Doping Agency, is a key target in drug tests, necessitating a pretreatment material capable of selectively, rapidly, and sufficiently separating/enriching analytes from complex matrices. Herein, a metal-mediated magnetic molecularly imprinted polymer (mMIP) was rationally designed and synthesized for the specific capture of FUR. The preparations involved the utilization of chromium (III) as the binding pivot, (3-aminopropyl)triethoxysilane as functional monomer, and Fe 3 O 4 as core, all assembled via free radical polymerization. Both the morphologies and adsorptive properties of the mMIP were characterized using multiple methods. The resulting Cr(III)-mediated mMIP (ChM-mMIP) presented excellent selectivity and specificity toward FUR. Under optimized conditions, the adsorption capacity reached 128.50 mg/g within 10 min, and the imprinting factor was 10.41. Moreover, it was also successfully applied as a dispersive solid-phase extraction material, enabling the detection of FUR concentration as low as 20 ng/mL in human urine samples when coupled with a high-performance liquid chromatography/photodiode array. Overall, this study offers a valuable strategy for the development of novel recognition material., (© 2024 Wiley‐VCH GmbH.)

The third trimester of pregnancy is related to physiological changes that can modify the process of absorption, distribution, metabolism, and excretion and, consequently, the efficacy and toxicity of drugs. However, little is known about furosemide pharmacokinetics and placental transfer in pregnancy. This study evaluated the maternal-fetal pharmacokinetics and distribution to amniotic fluid of furosemide in hypertensive parturient women under cesarean section. Twelve hypertensive parturient women under methyldopa (250 mg/8 h) and/or pindolol (10 mg/12 h) treatment received a 40-mg single oral dose of furosemide 1 to 10 hours before delivery by cesarean section. Blood and urine samples were collected for 12 hours after furosemide administration. At delivery, samples were obtained from maternal and umbilical cord blood (n = 8) to assess the transplacental transfer. Amniotic fluid (n = 4) was collected at the time of delivery. The following furosemide pharmacokinetic parameters were obtained as median (interquartile range): C max , 403 ng/mL (229 to 715 ng/mL); T max , 2.00 hours (1.50 to 4.83 hours); elimination half-life (t 1/2 ), 2.50 hours (1.77 to 2.97 hours); AUC 0-12 h , 1366 ng⋅h/mL (927 to 2531 ng⋅h/mL); AUC 0-∞ , 1580 ng⋅h/mL (1270 to 2881 ng⋅h/mL); CL/F 25.3 L/h (13.8 to 31.4 L/h); CLR, 2.50 L/h (1.77 to 2.97 L/h); CLNR, 22.7 L/h (12.1 to 25.6 L/h); and V d /F 82.8 L (34.4 to 173 L). The transplacental transfer of furosemide was 0.43 (0.10 to 0.73), and the amniotic fluid concentration was 11.0 ng/mL (5.51 to 14.6 ng/mL). From a clinical point of view, these results suggest that substrates of uridine diphosphate-glucuronosyltransferase isoenzymes such as furosemide may have increased clearance during pregnancy and could require dose adjustment in this population., (© 2020, The American College of Clinical Pharmacology.)

Many drug candidates have shown significant renoprotective effects in preclinical models; however, there is no clinically used effective pharmacotherapy for acute kidney injury. The failure to translate from bench to bedside could be due to misleading results from experimental animals with undetected congenital kidney defects. This study was performed to assess the effects of congenital hydronephrosis on the functional capacity of tubular renal transporters as well as kidney sensitivity to ischemia-reperfusion (I-R)-induced injury in male Wistar rats. Ultrasonography was used to distinguish healthy control rats from rats with hydronephrosis. L-carnitine or furosemide was administered, and serial blood samples were collected and analyzed to assess the effects of hydronephrosis on the pharmacokinetic parameters. Renal injury was induced by clamping the renal pedicles of both kidneys for 30 min with subsequent 24 hr reperfusion. The prevalence of hydronephrosis reached ~30%. The plasma concentrations after administration of L-carnitine or furosemide were similar in both groups. I-R induced more pronounced renal injury in the hydronephrotic rats than the control rats, which was evident by a significantly higher kidney injury molecule-1 concentration and lower creatinine concentration in the urine of the hydronephrotic rats than the control rats. After I-R, the gene expression levels of renal injury markers were significantly higher in the hydronephrotic kidneys than in the kidneys of control group animals. In conclusion, our results demonstrate that hydronephrotic kidneys are more susceptible to I-R-induced damage than healthy kidneys. Unilateral hydronephrosis does not affect the pharmacokinetics of substances secreted or absorbed in the renal tubules., (© 2020 The Authors. Physiological Reports published by Wiley Periodicals LLC on behalf of The Physiological Society and the American Physiological Society.)

Background: Interstitial fibrosis (IF) on kidney biopsy is one of the most potent risk factors for kidney disease progression. The furosemide stress test (FST) is a validated tool that predicts the severity of acute kidney injury (especially at 2 h) in critically ill patients. Since furosemide is secreted through the kidney tubules, the response to FST represents the tubular secretory capacity. To our knowledge there is no data on the correlation between functional tubular capacity assessed by the FST with IF on kidney biopsies from patients with chronic kidney disease (CKD). The aim of this study was to determine the association between urine output (UO), Furosemide Excreted Mass (FEM) and IF on kidney biopsies after a FST., Methods: This study included 84 patients who underwent kidney biopsy for clinical indications and a FST. The percentage of fibrosis was determined by morphometry technique and reviewed by a nephropathologist. All patients underwent a FST prior to the biopsy. Urine volume and urinary sodium were measured in addition to urine concentrations of furosemide at different times (2, 4 and 6 h). We used an established equation to determine the FEM. Values were expressed as mean, standard deviation or percentage and Pearson Correlation., Results: The mean age of the participants was 38 years and 44% were male. The prevalence of diabetes mellitus, hypertension and diuretic use was significantly higher with more advanced degree of fibrosis. Nephrotic syndrome and acute kidney graft dysfunction were the most frequent indications for biopsy. eGFR was inversely related to the degree of fibrosis. Subjects with the highest degree of fibrosis (grade 3) showed a significant lower UO at first hour of the FST when compared to lower degrees of fibrosis (p = 0.015). Likewise, the total UO and the FEM was progressively lower with higher degrees of fibrosis. An inversely linear correlation between FEM and the degree of fibrosis (r = - 0.245, p = 0.02) was observed., Conclusions: Our findings indicate that interstitial fibrosis correlates with total urine output and FEM. Further studies are needed to determine if UO and FST could be a non-invasive tool to evaluate interstitial fibrosis., Trial Registration: ClinicalTrials.gov NCT02417883.

Pharmaceuticals and their by-products are increasingly a matter of concern, because of their unknown impacts on human health and ecosystems. The lack of information on these transformation products, which toxicity may exceed that of their parent molecules, makes their detection and toxicological evaluation impossible. Recently we characterized the Pyridinium of furosemide (PoF), a new transformation product of furosemide, the most widely used diuretic and an emerging pollutant. Here, we reveal PoF toxicity in SH-SY5Y cells leading to alpha-synuclein accumulation, reactive oxygen species generation, and apoptosis. We also showed that its mechanism of action is mediated through specific inhibition of striatal respiratory chain complex I, both in vitro by direct exposure of striatum mitochondria to PoF, and in vivo, in striatal mitochondria isolated from mice exposed to PoF for 7 days in drinking water and sacrificed 30 days later. Moreover, in mice, PoF induced neurodegenerative diseases hallmarks like phospho-Serine129 alpha-synuclein, tyrosine hydroxylase decrease in striatum, Tau accumulation in hippocampus. Finally, we uncovered PoF as a new metabolite of furosemide present in urine of patients treated with this drug by LC/MS. As a physiopathologically relevant neurodegeneration inducer, this new metabolite warrants further studies in the framework of public health and environment protection., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Aims: Sacubitril/valsartan is indicated for the treatment of heart failure and reduced ejection fraction (HFrEF). Furosemide, a loop diuretic commonly used for the treatment of HFrEF, may be coadministered with sacubitril/valsartan in clinical practice. The effect of sacubitril/valsartan on the pharmacokinetics and pharmacodynamics of furosemide was evaluated in this open label, two-period, single-sequence study in healthy subjects., Methods: All subjects (n = 28) received 40 mg oral single-dose furosemide during period 1, followed by a washout of 2 days. In period 2, sacubitril/valsartan 200 mg (97/103 mg) was administered twice daily for 5 days and a single dose of 40 mg furosemide was coadministered on day 6. Serial plasma and urine samples were collected to determine the pharmacokinetics of furosemide and sacubitril/valsartan and the pharmacodynamics of furosemide. The point estimates and the associated 90% confidence intervals for pharmacokinetic parameters were evaluated., Results: Coadministration of furosemide with sacubitril/valsartan decreased the maximum observed plasma concentration (C max ) [estimated geometric mean ratio (90% confidence interval): 0.50 (0.44, 0.56)], area under the plasma concentration-time curve (AUC) from time 0 to infinity [0.72 (0.67, 0.77)] and 24-h urinary excretion of furosemide [0.74 (0.69, 0.79)]. When coadministered with sacubitril/valsartan, 0-4-h, 4-8-h and 0-24-h diuresis in response to furosemide was reduced by ~7%, 21% and 0.2%, respectively, while natriuresis was reduced by ~ 28.5%, 7% and 15%, respectively. Post hoc analysis of the pivotal phase III Prospective comparison of ARNI with ACEI to Determine Impact on Global Mortality and morbidity in Heart Failure trial (PARADIGM-HF) indicated that the median furosemide dose was similar at baseline and at the end of the study in the sacubitril/valsartan group., Conclusions: Sacubitril/valsartan reduced plasma C max and AUC and 24-h urinary excretion of furosemide, while not significantly affecting its pharmacodynamic effects in healthy subjects., (© 2018 Crown copyright. British Journal of Clinical Pharmacology © 2018 British Pharmacological Society.)

Introduction: Diuretic failure is a potential life-ending event but is unpredictable and poorly understood. The objectives of this study were to evaluate pharmacodynamic markers of furosemide-induced diuresis and to investigate mechanisms of diuretic braking in dogs receiving constant rate infusion (CRI) of furosemide., Animals: Six healthy male dogs., Methods: Raw data and stored samples from one arm of a previously published study were further analyzed to mechanistically investigate causes of diuretic braking in these dogs. Urine volume was recorded hourly during a 5-h furosemide CRI. Urine and blood samples were collected hourly to measure serum and urine electrolytes, urine aldosterone, and plasma and urine furosemide. Serum electrolyte fractional excretion was calculated. Urine sodium concentration was indexed to urine potassium (uNa:uK) and urine furosemide (uNa:uFur) concentrations, plasma furosemide concentration was indexed to urine furosemide concentration (pFur:uFur), and urine aldosterone was indexed to urine creatinine (UAldo:C). Temporal change and the relationship to urine volume were evaluated for these measured and calculated variables., Results: Urine volume was significantly correlated with urine electrolyte amounts and with uNa:uK. The ratio of pFur:uFur decreased during the infusion, whereas furosemide excretion was unchanged., Conclusions: There was a strong relationship between urine volume and absolute urine electrolyte excretion. Urine volume was strongly correlated to uNa:uK, giving it potential as a spot indicator of urine production during diuresis. The decrease in uNa:uK over time during the infusion is consistent with mineralocorticoid modification of urinary electrolyte excretion, supporting renin-angiotensin-aldosterone activation as a cause of diuretic braking in this model., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Furosemide is a diuretic agent used commonly in racehorses to attenuate the bleeding associated with exercise-induced pulmonary hemorrhage (EIPH). The current study describes serum and urine concentrations and the pharmacokinetics of furosemide following administration at 4 and 24 hrs prior to maximal exercise. Eight exercised adult Thoroughbred horses received a single IV administration of 250 mg of furosemide at 4 and 24 hrs prior to maximal exercise on a high-speed treadmill. Blood and urine samples were collected at time 0 and at various times for up to 72 hrs and furosemide concentrations determined using liquid chromatography-tandem mass spectrometry. Serum furosemide concentrations remained above the LOQ (0.05 ng/ml) for 36 hrs in 3/8 and 1/8 horses in the 4- and 24-hrs groups, respectively. Serum concentration data were best fit by a two-compartment model. There was not a significant difference in the volume of distribution at steady-state (0.594 ± 0.178 [4 hrs] and 0.648 ± 0.147 [24 hrs] L/kg) or systemic clearance (0.541 ± 0.094 [4 hrs] and 0.617 ± 0.114 [24 hrs] L/hrs/kg) between horses that were exercised at 4- and 24 hrs postdrug administration. The mean ± SD elimination half-life was 3.12 ± 0.387 and 3.23 ± 0.407 hrs following administration at 4 and 24 hrs prior to exercise, respectively., (© 2017 John Wiley & Sons Ltd.)

Electrolyte disorders due to tubular disorders are rare, and knowledge about validated clinical diagnostic tools such as tubular function tests is sparse. Reference values for tubular function tests are based on studies with small sample size in young healthy volunteers. Patients with tubular disorders, however, frequently are older and can have a compromised renal function. We therefore evaluated four tubular function tests in individuals with different ages and renal function. We performed furosemide, thiazide, furosemide-fludrocortisone, and desmopressin tests in healthy individuals aged 18-50 years, healthy individuals aged more than 50 years and individuals with compromised renal function. For each tubular function test we included 10 individuals per group. The responses in young healthy individuals were in line with previously reported values in literature. The maximal increase in fractional chloride excretion after furosemide was below the lower limit of young healthy individuals in 5/10 older subjects and in 2/10 patients with compromised renal function. The maximal increase in fractional chloride excretion after thiazide was below the lower limit of young healthy individuals in 6/10 older subjects and in 7/10 patients with compromised renal function. Median maximal urine osmolality after desmopressin was 1002 mosmol/kg H 2 O in young healthy individuals, 820 mosmol/kg H 2 O in older subjects and 624 mosmol/kg H 2 O in patients with compromised renal function. Reference values for tubular function tests obtained in young healthy adults thus cannot simply be extrapolated to older patients or patients with compromised kidney function. Larger validation studies are needed to define true reference values in these patient categories., (© 2017 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.)

Solid-phase membrane micro-tip extraction (SPMMTE) and capillary electrophoresis (CE) methods were developed and validated for analysis of chloramphenicol in human plasma and urine samples. Iron composite nanoparticles were prepared using green technology. CE was carried out using a silica capillary (60 cm × 50 μm i.d.), phosphate buffer (50 mm, 8.0 pH)-acetonitrile (95:5, v/v) as the background electrolyte, 10 kV voltage, 280 nm detection, 20 s injection time and 27 ± 1°C temperature. Frusemide was used as an internal standard. The values of migration time, electrophoretic mobility, electrophoretic velocity and theoretical plates of chloramphenicol were 12.254 min, 4.44 × 10, 7.41 × 10 and 11,227. The limits of detection and quantitation of chloramphenicol were 0.1 and 1.0 μg/mL. Recovery of chloramphenicol in the standard solution was 95%. Solid-phase membrane micro-tip extraction and capillary electrophoresis methods may be used to analyze chloramphenicol in human plasma and urine samples of any patient., (Copyright © 2016 John Wiley & Sons, Ltd.)

A novel electrochemical sensor based on a molecularly imprinted polymer, poly(o-phenylenediamine) (PoPD), has been developed for selective and sensitive detection of furosemide. The sensor was prepared by incorporating of furosemide as template molecules during the electropolymerization of o-phenylenediamine on a gold electrode. To develop the molecularly imprinted polymer (MIP), the template molecules were removed from the modified electrode's surface by washing it with 0.25 mol L(-1) NaOH solution. The imprinted layer was characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and atomic force microscopy (AFM). The sensor's preparation conditions including furosemide concentration, the number of CV cycles in the electropolymerization process, extraction solution of the template from the imprinted film, the incubation time and the pH level were optimized. The incubation of the MIP-modified electrode, with respect to furosemide concentration, resulted in a suppression of the K4[Fe(CN)6] oxidation process. Under the optimal experimental conditions, the response of the imprinted sensor was linear in the range of 1.0×10(-7)-7.0×10(-6) mol L(-1) of furosemide. The detection limit was obtained as 7.0×10(-8) mol L(-1) for furosemide by using this sensor. The sensor was successfully used to determine the furosemide amount in the tablet and in human urine samples with satisfactory results., (Copyright © 2015 Elsevier B.V. All rights reserved.)

A novel method is developed for the quantification of furosemide in biological fluids. The method is based on the electro-reduction of Zn(II)-furosemide complex at carboxyl-MWCNT modified glassy carbon electrode. It is shown that, in Britton-Robinson buffer (pH5.7) the reduction peak of Zn(II)-furosemide complex formed at -1.0 V (versus, Ag/AgCl). The increment of current signal obtained from the reduction peak current of the Zn(II)-furosemide complex was rectilinear with furosemide concentration in the range of 0.03 to 140.0 μg ml(-1), with a detection limit of 0.007 μg ml(-1). The drug recovery ranged between 97.8% and 100.8% and the mean drug recovery was 98.89%. The accuracies (relative error% and RSD%) were less than 15% and are acceptable according to the US FDA guideline for bioanalytical method validation. The sensor was used for quantification of furosemide in drug and biological fluid samples. The data of drug analysis were compared with the standard method., (Copyright © 2015 Elsevier B.V. All rights reserved.)

A high performance liquid chromatographic (HPLC) method was proposed for the simultaneous determination of four drugs for kidney disease, enalapril, triamterene, furosemide and valsartan. After proteins being removed by acetone precipitation method, freeze drying and redissolving in mobile phase, the urine samples were analyzed by HPLC. Chromatographic separation was performed on a WondaSil C18-WR (150 mm x 4.6 mm, 5 μm) in gradient elution mode using 10.0 mmol/L ammonium acetate aqueous solution (pH 3.90) and acetonitrile as mobile phases at a flow rate of 1.0 mL/min. The detection wavelength was set at 254 nm. Under the optimized conditions, good linearities were obtained in the range of 0.15-300 mg/L, 0.05-100 mg/L, 0.75-750 mg/L, 0.05-100 mg/L, and the detection limits were 1.38 x 10(-2), 7. 67x103, 3.69x 10-2, 1. 16x 10-2 mg/L for enalapril, triamterene, furosemide and valsartan, respectively. The recoveries were in the range of 89.49%-99.20% with the relative standard deviations (RSDs) among 4.12%-9.44%. The method is simple, accurate and effective, and the results showed the method is applicable for the analysis of the four drugs for kidney diseases in real urine samples.

Objective: To establish a method based on restricted access media-high performance liquid chromatography for direct online sample injection and detection of plasma and urine furosemide in rats., Methods: The column of restricted access media was used as the pre-treatment column and a C18 column as the analytical column. The mobile phase of the pre- treatment column was water-methanol (95:5, V/V) with a volume percentage of formic acid of 0.1%. The mobile phase of the analytical column was methanol-water (65:35, V/V) for plasma and methanol-water (55:45, V/V) for urine samples, all containing a volume percentage of formic acid of 0.1% with a flow rate of 1 ml/min. The detection wavelength was 274 nm and the column temperature was maintained at 25 degrees celsius., Results: The calibration curve showed an excellent linear relationship in rat plasma furosemide concentration range of 0.1-3.2 µg/ml (r=0.9995) and in urine concentration range of 0.5-32 µg/ml (r=0.9991). The average recoveries of furosemide at 3 spiked levels ranged from 101.82% to 113.36% for plasma and from 98.75% to 112.27% for urine samples. The detection showed good intra- and inter-day assay precisions and accuracies with the relative standard deviations all below 5%. The pharmacokinetic parameters AUC(0→24) was 6.265 g/(ml·h) with a t(1/2) of 2.447 h and a C(Max) of 1.414 g/ml. The mean cumulative excretory rate of furosemide in the urine of rats over 24 h was 32.50%-39.08%., Conclusion: Detection of furosemide in plasma and urine samples using restricted access media-high performance liquid chromatography is simple and efficient and allows direct online injection of the samples.

Perinatal growth restriction programs higher risk for chronic disease during adulthood via morphological and physiological changes in organ systems. Perinatal growth restriction is highly correlated with a decreased nephron number, altered renal function and subsequent hypertension. We hypothesize that such renal maladaptations result in altered pharmacologic patterns for life. Maternal protein restriction during gestation and lactation was used to induce perinatal growth restriction in the current study. The diuretic response of furosemide (2mg/kg single i.p. dose) in perinatally growth restricted rats during adulthood was investigated. Diuresis, natriuresis and renal excretion of furosemide were significantly reduced relative to controls, indicative of decreased efficacy. While a modest 12% decrease in diuresis was observed in males, females experienced 26% reduction. It is important to note that the baseline urine output and natriuresis were similar between treatment groups. The in vitro renal and hepatic metabolism of furosemide, the in vivo urinary excretion of the metabolite, and the expression of renal drug transporters were unaltered. Creatinine clearance was significantly reduced by 15% and 19% in perinatally growth restricted male and female rats, respectively. Further evidence of renal insufficiency was suggested by decreased uric acid clearance. Renal protein expression of sodium-potassium-chloride cotransporter, a pharmacodynamic target, was unaltered. In summary, perinatal growth restriction could permanently imprint pharmacokinetic processes affecting drug response., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Purpose: To systematically review clinical studies of co-administration of albumin and loop diuretics in hypoalbuminemic patients as a strategy to overcome diuretic resistance., Materials and Methods: Systematic search of electronic databases up to October 2012. We included randomized clinical trials of adults with hypoalbuminemia, comparing co-administration of loop diuretics and albumin versus loop diuretics alone. Quantitative data were synthesized with meta-analytic techniques for clinical, surrogate (urinary volume and urinary sodium excretion) and intermediate (pharmacokinetic and hemodynamic parameters) outcomes., Results: Ten studies were included, of which 8 trials with crossover design were synthesized with meta-analysis. A statistically significant increase in the amount of urine volume (increment of 231 mL [95% confidence interval 135.5-326.5]) and sodium excreted (15.9 mEq [4.9-26.8]) at 8 hours were found in favor of co-administration of albumin and furosemide. These differences were no longer statistically significant at 24 hours. Meta-analyses for intermediate outcomes (ie, furosemide excretion, distribution volume etc.) did not reveal statistically significant differences., Conclusions: Synthesis of a heterogeneous body of evidence shows transient effects of modest clinical significance for co-administration of albumin with furosemide in hypoalbuminemic patients. Pragmatic, large-scale randomized studies are needed to delineate the role of this strategy., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Furosemide is a loop diuretic frequently used to treat fluid overload conditions such as hepatic cirrhosis and congestive heart failure (CHF). A population-based meta-analysis approach in NONMEM® was used to develop a PK model characterizing the time-course of furosemide in plasma and excretion into the urine for healthy subjects and fluid overload patients. Furosemide PK data from healthy subjects receiving 80 mg of oral furosemide were supplemented with additional individual and aggregate plasma concentration and urinary excretion versus time data from the literature after intravenous (i.v.) or oral furosemide administration (10-500 mg) to healthy subjects or fluid overload patients. A three-compartment model with zero-order input following i.v. administration (or first-order absorption using a Weibull function after oral administration) and first-order elimination best described furosemide PK. A covariate analysis identified creatinine clearance (CL(CR)) as a statistically significant predictor of renal clearance (CL(R)), with a population mean CL(R) of 4.67, 3.11, 1.95 and 1.17 l/h for a subject with normal renal function (CL(CR) = 120 ml/min) or mild (CL(CR) = 80 ml/min), moderate (CL(CR) = 50 ml/min) or severe (CLCR  = 30 ml/min) renal impairment. Oral bioavailability was 59.1% and non-renal clearance was 2.02 l/h. A PC-VPC and other model diagnostics demonstrated that the population PK model can reasonably predict the rate of urinary furosemide excretion over time using dosing history and commonly available demographic data, allowing for convenient assessment of PK-PD relationships for furosemide when given alone or in combination with other agents used to treat fluid overload conditions., (Copyright © 2013 John Wiley & Sons, Ltd.)

Objective: We conducted a pharmacokinetic (PK) study and a pharmacodynamic (PD) study to assess whether Roux-en-Y gastric bypass (RYGB) surgery is associated with significant changes to PK and PD of oral medications., Background: The effect of RYGB on oral drug disposition is not well understood., Methods: An oral cocktail of probe drugs for major drug-metabolizing enzymes (caffeine, tolbutamide, omeprazole, dextromethorphan, and oral and intravenous midazolam) was administered to 18 RYGB recipients and 18 controls. Timed blood and urine samples were obtained for PK analyses. Forty mg of oral furosemide was administered to 13 RYGB recipients and 14 controls, and urine and blood samples were collected for assessing furosemidePK, and urine volume and urine sodium excretion for PD analyses., Results: Compared with controls, the RYGB group had significantly lower time to maximum plasma concentration (tmax) for caffeine (0.58 ± 0.5 vs 2.1 ± 2.2 hours, P < 0.0001), tolbutamide (1.4 ± 1.8 vs 2.1 ± 2.2 hours, P = 0.0001), omeprazole (1.1 ± 1.1 vs 4.4 ± 1.3 hours, P < 0.0001), and oral midazolam (0.5 ± 0.2 vs 0.7 ± 0.4 hours, P < 0.01). However, maximum plasma concentration, half-life, area under the curve, and oral bioavailability were not different. Compared with controls, the RYGB group had brisk natriuresis, with significantly lower tmax for urine sodium (1.3 ± 0.5 vs 3.1 ± 2.3 hours, P < 0.02) and correspondingly lower tmax for furosemide (1.8 ± 0.3 vs 4.2 ± 1.2 hours, P = 0.006). However, 6-hour urine sodium and 6-hour urine volume were not different between the two groups., Conclusions: RYGB recipients have significantly shorter tmax for the studied orally administered medications, but otherwise no other significant changes in PK were reported.

Objective: To evaluate the effect of administration of the labeled dosage of pimobendan to dogs with furosemide-induced activation of the renin-angiotensin-aldosterone system (RAAS)., Animals: 12 healthy hound-type dogs., Procedures: Dogs were allocated into 2 groups (6 dogs/group). One group received furosemide (2 mg/kg, PO, q 12 h) for 10 days (days 1 to 10). The second group received a combination of furosemide (2 mg/kg, PO, q 12 h) and pimobendan (0.25 mg/kg, PO, q 12 h) for 10 days (days 1 to 10). To determine the effect of the medications on the RAAS, 2 urine samples/d were obtained for determination of the urinary aldosterone-to-creatinine ratio (A:C) on days 0 (baseline), 5, and 10., Results: Mean ± SD urinary A:C increased significantly after administration of furosemide (baseline, 0.37 ± 0.14 μg/g; day 5, 0.89 ± 0.23 μg/g) or the combination of furosemide and pimobendan (baseline, 0.36 ± 0.22 μg/g; day 5, 0.88 ± 0.55 μg/g). Mean urinary A:C on day 10 was 0.95 ± 0.63 μg/g for furosemide alone and 0.85 ± 0.21 μg/g for the combination of furosemide and pimobendan., Conclusions and Clinical Relevance: Furosemide-induced RAAS activation appeared to plateau by day 5. Administration of pimobendan at a standard dosage did not enhance or suppress furosemide-induced RAAS activation. These results in clinically normal dogs suggested that furosemide, administered with or without pimobendan, should be accompanied by RAAS-suppressive treatment.

The ultra high performance liquid chromatography (UHPLC)-UV method for the simultaneous determination of furosemide, saluamine (furosemide metabolite), spironolactone, carnenone (spironolactone active metabolite), terbinafine, N-desmethylcarboxy terbinafine (terbinafine metabolite) and vancomycin in human plasma and urine is proposed. Good separation of the analytes was achieved with the gradient RP-UHPLC-UV with the mobile phase composed as acetonitrile and 0.1% formic acid. The determined substances were eluted from a Hypersil GOLD C(18)e (50 mm x 2.1 mm, 1.7 microm particles) column in 3.3 min. Good linear relationships were observed for all of the analytes (R(2) higher than 0.994). The limit of detection (LOD) values varied from 0.01 to 0.07 microg ml(-1), with vancomycin as an exception (0.11 microg ml(-1)). After protein precipitation and solid-phase extraction, samples of plasma and urine were analyzed. Thanks to the short analysis time and small quantities of urine or plasma needed, this method can be applied to routine clinical analysis.

Modified methods for the detection and measurement of furosemide and spironolactone in biological fluids has been developed based on gas chromatography mass spectrometry. Optimal conditions for chromatography are described for the determination of the diuretic agents of interest. The proposed methods were verified by analysing urine samples obtained from patients with chronic cardiac insufficiency.

In competition sports, a diuretic is a substance widely prohibited by the World Anti-Doping Agency (WADA). In this paper, a sensitive, rapid and convenient analytical method for the determination of acidic [furosemide (FUROS) and bumetanide (BUMET)] and basic [triamterene (TRIAM)] diuretics in human urine was developed by hollow fiber-based liquid-liquid-liquid microextraction (LLLME) coupled with HPLC-UV. The LLLME conditions, such as the organic extraction solvent, the acidity and basicity of the donor- and acceptor-phases, stirring speed, extraction time and ionic strength, were studied in detail. Under the optimum conditions, the linear ranges of furosemide, bumetanide and triamterene were 1.2-250, 5.0-250 and 5.0-500 ng mL(-1), respectively. The detection limits were 0.5 ng mL(-1) for furosemide, 1.2 ng mL(-1) for bumetanide and 2.0 ng mL(-1) for triamterene. The LLLME obtained a great improvement of the detection limits for all the analytes considered here, to the ng mL(-1) level, which almost reaches the level of the LC-MS method. This new LLLME method provided very high enrichments: 117-fold for furosemide, 175-fold for bumetanide and 68-fold for triamterene. Since the hollow fiber membrane was sealed, it could be used for extracting the diuretics directly from 'dirty' human urine samples without any clean-up procedures. With LLLME-HPLC, the corresponding recoveries ranged from 79.2 to 109% with the RSDs not exceeding 5.5% for the three diuretics in the spiked urine samples. The method was successfully applied to analyse the amounts of the three diuretics in real urine samples of volunteers after oral drug-taking. This new method proves to be sensitive and reliable and thus renders a very suitable means for the determination of trace diuretics in human urine based on the common HPLC instrument.

Blacks have a greater tendency to retain Na than whites. The present study sought evidence for ethnic differences in parameters reflective of Na uptake by the Na,K,2Cl cotransporter in the thick ascending limb, namely, the urine concentration and urinary excretion of certain cations before and after furosemide administration (40 mg IV). Subjects were healthy (ages 18 to 36 years). During the preceding overnight period, urine volume was lower, and osmolality was higher in blacks than in whites, an ethnic difference that disappeared when water intake was restricted to infused normal saline (60 mL/h). Plasma vasopressin levels were higher in black males than in other sex/ethnic groups. Baseline urinary excretion rates of K, Ca, and Mg were significantly lower in blacks than in whites. After furosemide (0 to 1 hour), K and Ca excretion rates increased, but the proportionate ethnic difference decreased from 44% to 22% and from 22% to 10%, respectively, consistent with blacks having more basal Na,K,2Cl cotransporter activity to inhibit. During a later postfurosemide period (1 to 5 hours), urinary concentrations of Ca and Mg recovered more slowly in blacks, consistent with greater reuptake in the thick ascending limb. In summary, there were distinct ethnic differences in renal handling of Ca and Mg basally and in response to furosemide that were consistent with a more active Na,K,2Cl cotransporter in the thick ascending limb in blacks. An increase in vasopressin levels appeared to explain greater urine concentrations in black males but not black females.

Introduction: Glomerular filtration rate (GFR) is an important parameter for studying drug-induced impairments on renal function in rats. The GFR is calculated from the concentration of creatinine and blood urea nitrogen (BUN) in serum and in urine, respectively. Following current protocols serum and urine samples must be taken from the same animal. Thus, in order to determine time-dependent effects it is necessary to use for each time point one separated group of animals. We developed a statistical test which allows analyzing the GFR from two different groups of animals: one used for repeated serum and the other one used for repeated urine analysis., Methods: Serum and urine samples were taken from two different sets of rats which were otherwise treated identically, i.e. drug doses, routes of administration (per os or per inhalation) and tap water loading. For each dose group GFR mean, standard deviation and statistical analysis to identify differences between the dose groups were determined., Results: After determination of the optimal time points for measurements, the effect on GFR of the three reference compounds, furosemide, hydrochlorothiazide and formoterol, was calculated. The results showed that the diuretic drugs furosemide and hydrochlorothiazide decreased the GFR and the antidiuretic drug formoterol increased the GFR, as counter regulation on urine loss or urine retention, respectively., Discussion: A mathematical model and the corresponding algorithm were developed, which can be used to calculate the GFR, and to test for differences between groups from two separated sets of rats, one used for urine, and the other one for serum analysis. This new method has the potential to reduce the number of animals needed and to improve the quality of data generated from various groups of animals in renal function studies.

The role of ATP-binding cassette transporters in the urinary excretion of diuretics was investigated. Significant ATP-dependent uptake of hydrochlorothiazide (HCT) and furosemide was observed in membrane vesicles that expressed multidrug resistance-associated protein 4 (MRP4) and breast cancer resistance protein (BCRP). Unlike taurocholate uptake, S-methylglutathione had no effect on the ATP-dependent uptake of both compounds by MRP4. The functional importance of MRP4 and BCRP in the urinary excretion of HCT and furosemide was investigated using gene knockout mice. The renal clearance of HCT and furosemide was reduced significantly but not abolished in Mrp4 knockout mice compared with wild-type mice (9.0 +/- 0.9 versus 15 +/- 2 ml/min per kg for HCT and 1.9 +/- 0.3 versus 2.7 +/- 0.1 ml/min per kg for furosemide), and the amount of HCT that was associated with the kidney specimens was greater in Mrp4 knockout mice (21 +/- 3 versus 13 +/- 1 nmol/g kidney). In contrast, Bcrp makes only a negligible contribution because the urinary excretion was unchanged in Bcrp knockout mice. Our results suggest that Mrp4, together with other unknown transporters, accounts for the luminal efflux of HCT and furosemide from proximal tubular epithelial cells.

Objective: To investigate the diuretic, natriuretic and kaliuretic effects of the antihypertensive Ayurveda drug Karavi Panchaka decoction and compare it with the diuretic frusemide., Design: An animal study using Sprague-Dawley rats. The volume of urine and the total sodium and potassium excreted in the urine by rats in response to orally fed Karavi Panchaka decoction were compared with rats fed with frusemide. Control experiments were done with rats receiving similar volumes of distilled water orally. The Ayurveda drug was prepared in accordance with the traditional method in the laboratory using medicinal plant specimens individually collected and identified., Measurements: The volume of urine excreted during a 24-hour period following administration of the Ayurveda drug, frusemide or water was measured. The total sodium and potassium ion concentrations in the urine samples were determined using flame photometry., Results: The Karavi Panchaka decoction clearly showed a statistically significant increase in urine excretion when compared with the control group that received only distilled water. The potassium ion excretion was significantly increased in the Karavi Panchaka decoction treated group when compared to the control group. This increase was statistically similar to that caused by frusemide. Neither drug had a significant effect on sodium ion excretion at the dosages used., Conclusion: Our results show that the Karavi Panchaka decoction significantly increases urine and potassium ion excretion in rats, but has no effect on sodium ion excretion at the dosage used. The effect of the Ayurveda drug on urine output as well as the sodium and potassium ion excretion is similar to that of frusemide administered at the dose used in our study.

In the present study we developed a fast and reliable HPLC assay for the determination of the loop diuretic furosemide in plasma and urine, using a Chromolith RP 18e (100 mm x 4.6 mm) monolithic silica rod HPLC column. After liquid-liquid extraction with diethylether plasma or urine samples were separated with a gradient consisting of solvent A (20% acetonitrile) and solvent B (80% acetonitrile), both in 0.25% acetic acid. The flow rate was 3.5 ml/min and the effluent was monitored by fluorescence with excitation at 230 nm and emission at 410 nm. The retention times for the internal standard (naproxen) and for furosemide were 2.1 and 3.7 min, respectively, and total run time was 8 min. The calibration curves were linear between 7.8 and 1000 ng/ml, and within-assay and between-assay coefficients of variation were <6.5% and <10%, respectively. The proposed assay for furosemide in plasma and urine using monolithic silica rod chromatography is fast, sensitive, and reliable, and, thus, well suited for pharmacokinetic studies.

Multicommutation implemented with flow-through optosensors is a very promising area of research. This recent approach benefits from the advantages of both methods and results in high sensitivity, selectivity, and speed, and little waste generation. This paper reports the simultaneous determination of furosemide and triamterene, two widely used diuretics, by measurement of their native fluorescence. The system has been proved to be useful for determination of both analytes in pharmaceutical preparations and for determination of triamterene in human urine and serum. A minicolumn filled with Sephadex SPC-25 microbeads was used to achieve separation of both analytes before detection in a flow-through cell filled with the same resin. The sensor is linear in the range 50-1200 and 0.4-8 ng mL(-1) with detection limits of 15 and 0.1 ng mL(-1) for furosemide and triamterene, respectively.

Background and Methods: Loop diuretic therapy is an essential part of chronic systolic heart failure (CH)F management, yet response to treatment can be variable. We analysed diuretic responsiveness in 39 stable patients with CHF in the community over 2 years. We measured serum ACE as a marker of adherence to ACE inhibitor therapy and urinary furosemide as a marker of diuretic adherence and action. Patients' clinical outcome was stable and not hospitalized (Group 0); alive but hospitalized (Group 1); or dead during follow up (Group 2)., Results: Prescribed furosemide dose was variable (range 20-370 mg generally once daily) and progressive dose increments were common. Failed furosemide adherence (defined as < 10% of a dose excreted in 24 h urine where normal average excretion = 50% of an oral dose) during static prescribed dosing was infrequent relative to all days of therapy; yet was equally common across all outcome groups. Furosemide non-adherence appeared to be independent of non-adherence with ACE inhibitor (as marked by serum ACE activity > 20 U l(-1)) treatment. Furosemide responsiveness (mm of sodium excreted per mg furosemide in urine) showed no relationship to prescribed dose and paradoxically tended to rise in patients with higher basal aldosterone concentrations. Furosemide responsiveness fell by outcome class despite increased dose. Within-patient responsiveness remained relatively constant although highly variable between individuals., Conclusions: Furosemide responsiveness varied greatly between individuals but was constant within an individual. Non-adherence with furosemide was less common among those who died and appeared to occur at different time points from non-adherence with ACE inhibitor treatment, which was slightly more common in all outcome groups. Patients who died were prescribed higher furosemide doses and had greater furosemide excretion yet had similar sodium excretion. The main factor in response to chronic furosemide therapy was intrarenal diuretic resistance. Gross non-adherence was less important.

Continuous rate infusion (CRI) of furosemide in humans is considered superior to intermittent administration (IA). This study examined whether furosemide CRI, compared with IA, would increase diuretic efficacy with decreased fluid and electrolyte fluctuations and activation of the renin-angiotensin-aldosterone system (RAAS) in the horse. Five mares were used in a crossover-design study. During a 24-hour period, each horse received a total of 3 mg/kg furosemide by either CRI (0.12 mg/kg/h preceded by a loading dose of 0.12 mg/kg IV) or IA (1 mg/kg IV q8h). There was not a statistically significant difference in urine volume over 24 hours between methods; however, urine volume was significantly greater after CRI compared with IA during the first 8 hours ([median 25th percentile, 75th percentile]: 9.6 L [8.9, 14.4] for CRI versus 5.9 L [5.3, 6.0] for IA). CRI produced a more uniform urine flow, decreased fluctuations in plasma volume, and suppressed renal concentrating ability throughout the infusion period. Potassium, Ca, and Cl excretion was greater during CRI than IA (1,133 mmol [1.110, 1,229] versus 764 mmol [709, 904], 102.7 mmol [96.0, 117.2] versus 73.3 mmol [65.0, 73.5], and 1,776 mmol [1,657, 2.378] versus 1,596 mmol [1,457, 1,767], respectively). Elimination half-lives of furosemide were 1.35 and 0.47 hours for CRI and IA, respectively. The area under the excretion rate curve was 1,285.7 and 184.2 mL x mg/mL for CRI and IA, respectively. Furosemide CRI (0.12 mg/kg/h) for 8 hours, preceded by a loading dose (0.12 mg/kg), is recommended when profound diuresis is needed acutely in horses.

Several studies in human subjects have demonstrated greater diuresis with constant rate infusion (CRI) furosemide than intermittent bolus (IB) furosemide. This study was conducted to compare the diuretic efficacy of the same total dose of IB furosemide and CRI furosemide in 6 healthy, adult Greyhound dogs in a randomized crossover design with a 2-week washout period between treatments. For IB administration, dogs received 3 mg/kg at 0 and 4 hours. For CRI administration, dogs received a 0.66 mg/kg loading dose followed by 0.66 mg/kg/h over 8 hours. The same volume of fluid was administered for both methods. Urine output was quantified hourly. Urine electrolyte concentrations, urine specific gravity (USG), packed cell volume (PCV), total protein (TP), serum electrolyte concentrations, total carbon dioxide (TCO2), serum creatinine (sCr), and blood urea nitrogen (BUN) were determined every 2 hours. Urine production and water intake were greater (P < or = 0.05) for CRI than IB. Urine sodium and calcium losses were greater (P < 0.05) and urine potassium loss was less (P = 0.03) for CRI than IB, but there was no evidence of a difference between methods for urine magnesium and chloride losses. Serum chloride concentration was less (P < 0.001), sCr concentration greater (P = 0.04). TP greater (P = 0.01), and PCV greater (P = 0.003) for CRI than IB. No differences in USG, TCO2, BUN, or serum potassium, sodium, and magnesium concentrations were detected between methods. The same total dose of CRI furosemide resulted in more diuresis, natriuresis, and calciuresis and less kaliuresis than IB furosemide in these normal Greyhound dogs over 8 hours, suggesting that furosemide is a more effective diuretic when administered by CRI than by IB.

A 32-year-old woman with a three-year history of muscle weakness and hypokalemia, was admitted to our hospital because of hypokalemic periodic paralysis. Clinical and laboratory findings were consistent with Bartter's syndrome. Although she denied any ingestion of diuretics substantial quantities of furosemide were detected in her urine. She had been drinking health tea which contained about 90 mg of furosemide per teabag daily for five years. Four years after discontinuation of drinking the tea, the hypokalemia was completely ameliorated, but poor renal concentration ability is still present. We conclude that is a case of pseudo-Bartter's syndrome that was caused by long-term ingestion of the health tea supplemented illegally with furosemide, and suspect that such cases may be observed more frequently than currently thought.

Background: The optimal dosing strategy for continuous intravenous furosemide infusion is unknown in pediatric patients. Eighteen patients less than 1 year old were studied after cardiac surgery during routine clinical care. The current strategy starts with a continuous infusion of 0.1 mg/kg x h, which may be adapted., Methods: A pharmacokinetic-pharmacodynamic model was developed that linked furosemide dose to furosemide serum concentrations, renal function (creatinine clearance), and urine output. Various regimens were simulated that adapt according to urine production. The modified dosing schedule was prospectively tested in a subsequent population of 18 pediatric patients after cardiac surgery., Results: Data from the follow-up study suggest that urine production is more controlled for the proposed regimen., Conclusions: Both the modeling and simulation results and the follow-up study indicated that a bolus dose of 1 mg/kg followed 6 hours later with a 1- or 2-mg/kg loading dose and a 0.2-mg/kg x. h intravenous infusion provides a rational starting point for furosemide therapy after cardiac surgery in pediatric patients less than 1 year old. Adjustment of this regimen every 12 hours in steps of 0.1 mg/kg x h on the basis of clinical assessment should lead to adequate control over urinary output.

Furosemide, a drug that promotes urine excretion, is used in the pharmacotherapy of various diseases and is considered as a doping agent in sports. Using alkaline electrolytes, analysis of furosemide by dodecyl sulfate based micellar electrokinetic capillary chromatography (MECC) and capillary zone electrophoresis (CZE) with laser-induced fluorescence detection (LIF, analyte excitation with the 325 nm line of a HeCd laser) is described. Data produced by injection of plain or diluted patient urines are confirmed with those obtained via analysis of urinary solid-phase extracts. CZE-LIF and MECC-LIF are thereby shown to permit unambiguous recognition of furosemide in urines collected after ingestion of therapeutic doses of this drug. This is in contrast to solute detection via UV absorbance for which the extraction of furosemide is required. MECC based electropherograms are somewhat more complex compared to those obtained by CZE-LIF, this suggesting that the latter approach is more suitable for rapid screening of urines with direct sample injection and LIF detection. Alternatively, capillary electrophoresis with negative electrospray ionization-ion-trap tandem mass spectrometry (CE-MS2) is shown to permit the direct confirmation of furosemide in human urine. This approach is based upon the monitoring of the m/z 329.3-->4m/z 285.2 precursor-product ion transition. CZE-LIF and CE-MS2 with injection of plain or diluted urine represent simple, rapid and attractive urinary screening and confirmation assays for furosemide in patient urines.

The importance of considering sex differences in drug handling studies was admitted recently. The present work evaluates the sex influences on the pharmacokinetics of para-aminohippuric acid (PAH), the reference substance for the renal organic anion transports systems, and furosemide (FS), a standard loop diuretic which is also a substrate for this transport system. Female rats displayed a lower PAH and FS systemic clearance, and a lower value of the elimination rate microconstant from the central compartment for both drugs. These results may be explained by the diminution of the renal clearance of both PAH and FS observed in females. In summary, sex modifies the pharmacokinetics of organic anions. Although additional experimental work must be done to bridge the gap between studies using animals and humans, the reported experimental observations may have potentially important pharmacological implications. So, caution must be exercised in administering drugs like organic anions to females., (Copyright 2002 Elsevier Science Ltd.)

A sensitive, selective and efficient micellar liquid chromatographic (MLC) procedure was developed for the determination of furosemide (4-chloro-N-furfuryl-5-sulfamoylanthranilic acid) in urine samples by direct injection and UV detection. The procedure makes use of a C18 reversed-phase column and a micellar mobile phase of 0.05 mol l(-1) sodium dodecyl sulfate-6% v/v propanol and phosphate buffer at pH 3 to resolve furosemide from its photochemical degradation products. The importance of protecting the standards and urine samples to be analysed from light in the assay of furosemide, avoiding its degradation, was verified. The limit of quantification was 0.15 microg ml(-1) and the relative standard deviation of the inter-day assay was 0.8-0.04% in the 6-82 microg ml(-1) range. Detection of urinary excretion of furosemide was followed up to 12 h after ingestion of the drug by a healthy volunteer. No potential interference from the major metabolite (furosemide acylglucuronide) and its hydrolytic product (4-chloro-5-sulfamoylanthranilic acid) was observed. Commonly administered drugs also did not interfere. The proposed MLC procedure permits the rapid and reproducible measurement of low levels of furosemide in a small amount of urine.

Objective: To estimate the probability of concurrently exceeding thresholds for plasma concentration of furosemide and urine specific gravity after IV administration of furosemide in horses., Animals: 12 mature healthy Thoroughbred (n = 6) or Quarter Horse (6) mares., Procedure: Venous blood was collected from each horse prior to and 0.25, 0.5, 0.75, 1, 2, 3, 4, 4.5, 5, and 6 hours after IV administration of 250 mg (first experiment) or 500 mg (second experiment) of furosemide. Urine was collected hourly between 1 and 6 hours after administration of furosemide at both doses. Concentrations of furosemide were determined by use of an ELISA. Concentration of furosemide and urine specific gravity was modeled as a function of time, accounting for inter- and intrahorse variabilities. On the basis of pharmacokinetic and specific gravity data, the probability of exceeding a concentration of 100 ng of furosemide/ml as a function of time was determined, using a semiparametric smooth functional averaging method. A bootstrap approach was used to assess the inherent variation in this estimated probability., Results: The estimated probability of exceeding the threshold of 100 ng of furosemide/ml and urine specific gravity < 1.012 was approximately 0% between 4.0 and 5.5 hours after IV administration of 250 mg of furosemide/horse, and ranged from 0 to 1% between 4 and 5.5 hours after IV administration of 500 mg of furosemide/horse. The probability of a horse being falsely identified as in violation of regulatory concentrations was inversely associated with time., Conclusions and Clinical Relevance: Coupling plasma furosemide concentration with urine specific gravity testing will greatly reduce the chance that some horses are misclassified as being in violation of regulatory concentrations.

Hypoalbuminemic patients often have sufficient fluid accumulation to mandate diuretic therapy but are often resistant to diuresis. Studies have suggested that hypoalbuminemia itself impairs delivery of effective amounts of diuretic agent into the urine, the site of action. Therefore, administration of mixtures of albumin and loop diuretics may enhance responses. Thirteen patients with biopsy-proven cirrhosis and ascites (age, 51.2 +/- 8.1 yr; Child-Pugh score, 8.5 +/- 1.0; serum albumin concentration, 3.0 +/- 0.6 g/dl) were studied in this randomized crossover study. Sodium balance was maintained throughout the study with a metabolic diet. All patients received spironolactone, but administration of all other diuretic agents was discontinued. Each patient received all of the following four treatments intravenously: (1) 40 mg of furosemide, (2) 25 g of albumin, (3) 40 mg of furosemide and 25 g of albumin premixed ex vivo, and (4) 40 mg of furosemide and 25 g of albumin infused simultaneously into different arms. Responses were assessed by measuring urinary sodium excretion and relating the urinary furosemide excretion rate to the sodium excretion rate. Additionally, the pharmacokinetics of furosemide were assessed. Furosemide pharmacokinetics were similar for all treatment arms. Albumin alone had negligible diuretic effects. Neither albumin regimen increased the response to furosemide. Moreover, the relationship between the urinary furosemide excretion rate and the sodium excretion rate was unaffected by albumin. In conclusion, albumin failed to enhance the diuretic effects of furosemide in cirrhotic patients with ascites. Therefore, the coadministration of albumin and furosemide for the treatment of cirrhosis, and likely other hypoalbuminemic conditions, should not be used clinically.

For the purpose of enhancement the bioavailability of furosemide (FR), a floating dosage form with controlled release of FR was designed in this study. Because of the lower solubility of active material in the gastric medium, it was first enhanced by preparing an inclusion complex of FR with beta-cyclodextrin (beta-CD) in a 1:1 proportion using the kneading method. Following the design of dosage form, bilayer floating tablets were prepared. After dissolution rate studies were performed using the continuous flow-through cell method, the formulation that provided delivery of active material near the target profile was given to six healthy male volunteer subjects, and in vivo tests were performed. It was determined by radiographs that floating tablets prepared by adding BaSO4 stayed in the stomach for 6 hr. Further, values of the area under the plasma concentration-time curve (AUC) obtained with the floating dosage form were about 1.8 times those of the conventional FR tablet in blood analyses; maximum and minimum plasma concentrations were also found to be between the desired limits. In urine analyses, the peak diuretic effect seen in classical preparations was decreased and prolonged in floating dosage forms. Also, a considerably significant correlation was detected between in vivo results and in vitro data of the dissolution rate, and it was concluded that the modified continuous flow-through cell method is usable for in vitro dissolution rate tests of floating dosage forms.

The authors examined the natriuretic efficiency of furosemide in rats with cirrhosis induced by carbon tetrachloride (CCl(4)). Rats were treated for 17 weeks with intraperitoneal injections of CCl(4) in groundnut oil twice a week throughout the study. Control rats were treated with vehicle (groundnut oil). Studies in metabolic cages showed that sodium retention was present from week 14. Renal clearance experiments were performed in chronically, instrumented conscious rats at the end of week 14 and at the termination of the study (end week 16) when ascites and hyponatremia were present. After 14 weeks, cirrhotic rats had sodium retention along with increased renal plasma flow, normal GFR, normal renal lithium handling, and a significantly increased diuretic (+41% vs. control) and natriuretic (+56% vs. control) response to a test dose furosemide (7.5 mg/kg b.w., intravenously). The natriuretic efficiency of furosemide, i.e., the natriuresis expressed relative to the furosemide excretion rate (triangle upU(Na)V/U(FUR)V) was increased by 51% versus control. After 17 weeks, ascites and hyponatremia had developed, and significant decreases in renal plasma flow (-33%), GFR (-30%), and fractional lithium excretion (-44%) were observed. At this stage urinary recovery of furosemide was significantly decreased and the diuretic (-27% vs. Control) and natriuretic (-38% vs. control) responses to furosemide were significantly impaired. However, the increased natriuretic efficiency of furosemide was still present (+34% vs. control). Together these results suggest that increased sodium reabsorption in the thick ascending limb of Henle's loop is involved in the renal sodium retention in cirrhosis in rats that eventually results in decompensation with the formation of ascites.

Response to loop diuretics in patients with nephrotic syndrome (NS) is subnormal. Studies in animal models of NS have suggested that binding of diuretic to urinary albumin is one of the mechanisms that may be operative in this diuretic resistance. To explore this hypothesis, 12 patients with NS were studied to determine whether displacement from urinary protein binding with sulfisoxazole would restore response to 120 mg of furosemide. The study was stopped after treating seven patients because it was clear that sulfizoxazole had no effect. Sodium excretion (mean +/- SD) from furosemide alone was 239 +/- 90 versus 240 +/- 115 mEq/8 h with sulfisoxazole. Sulfisoxazole had modest effects on serum pharmacokinetics of furosemide but had no effect on either the time course of furosemide urinary excretion or overall amount excreted: 49 +/- 15 mg versus 54 +/- 12 mg for furosemide alone and furosemide plus sulfisoxazole, respectively. It is concluded that urinary protein binding of loop diuretics is not a major mechanism for the diuretic resistance of NS. In turn, strategies aimed at displacing such binding are unlikely to be clinically helpful.

To investigate how the response to a bolus and an infusion of furosemide is modulated by the rate of fluid replacement and by hypoalbuminemia, rabbits received 5 mg/kg of furosemide as a bolus or infused over 60 min, whereas diuresis was replaced with 13, 121, or 238 ml/h NaCl 0.9%/glucose 5% (50:50). Natriuretic and diuretic efficiencies were greater with the infusion than with the bolus of furosemide. Fluid replacement increased natriuretic and diuretic efficiency of furosemide bolus but only diuretic efficiency of furosemide infusion. Furosemide net fluid depletion reached a plateau when fluid replacement increased beyond 121 ml/h. Repeated plasmapheresis decreased plasma albumin by 30% (P <.05) and increased furosemide unbound fraction (P <.05). Compared with control rabbits, hypoalbuminemia decreased the natriuresis of the bolus (22.7 +/- 1.5-16.6 +/- 1.3 mmol, P <.05) but not that elicited by furosemide infusion (26.2 +/- 1.8 mmol). Given as a bolus, furosemide natriuretic and diuretic response as a function of its urinary rate of excretion exhibited an hyperbolic relationship, and after its infusion a clockwise hysteresis, denoting tolerance. Plasma renin activity was increased by the bolus and the infusion of furosemide, even in the presence of 121 ml/h of fluid replacement. It is concluded that: 1) the increase in natriuretic/diuretic efficiency of the bolus induced by fluid replacement is greater than when furosemide is infused, 2) furosemide net effect does not increase proportionally to fluid replacement, and 3) the infusion of furosemide prevents the hypoalbuminemia-induced decrease in response of furosemide given as a bolus.

The objectives of this study were to determine the effect of phenylbutazone premedication on the pharmacokinetics and urinary excretion of frusemide in horses; and on frusemide-induced changes in urinary electrolyte excretion. Six Standardbred mares were used in a 3-way crossover design. The pharmacokinetics and renal effects of frusemide (1 mg/kg bwt i.v.) were studied with and without phenylbutazone premedication (8.8 mg/kg bwt per os 24 h before, followed by 4.4 mg/kg bwt i.v. 30 min before frusemide administration). A control (saline) treatment was also studied. Administration of frusemide without phenylbutazone led to diuresis, natriuresis, kaliuresis and chloruresis, and altered the ratio of sodium:chloride excretion from 0.4 to 1.0 in the first hour of diuresis. When frusemide and phenylbutazone were administered, sodium and chloride excretion in the first hour were significantly (P<0.05) reduced by 40 and 32%, respectively, when compared to frusemide administrationwithout phenylbutazone. The fractional clearance of sodium and chloride was also significantly reduced. Potassium excretion, potassium fractional clearance and the ratio of sodium to chloride excretion were not affected by administration of phenylbutazone. During peak diuresis, phenylbutazone did not affect the efficiency of frusemide with respect to electrolyte excretion. The plasma disposition of frusemide was not affected by phenylbutazone. However, the renal excretion of frusemide decreased by approximately 25%. We conclude that the decreased urinary excretion of frusemide by phenylbutazone led to an attenuation of frusemide-induced increases in urinary excretion of sodium and chloride. Since the efficiency of frusemide was not affected by phenylbutazone, we conclude that phenylbutazone attenuates the renal excretion of frusemide without inhibiting the intrarenal activity of frusemide in horses.

Simplified reversed-phase high-performance liquid chromatographic method with ultraviolet detection at 280 nm without extraction procedure is described to quantify furosemide in rabbit and human urine. An internal standard was not used. The lower limit of quantitation was 0.750 microg/ml using 50 microl urine samples (100 microl of total injection volume), and linear response was tested from 0.750 to 250 microg/ml in both humans and rabbits. Within and between-day accuracy and precision were always below 10% at all analyzed concentrations. Validation data showed that this method is linear, sensitive, selective, specific, accurate and reproducible.

We examined the effect of a new long-acting release formula (LAR) of the somatostatin analogue, octreotide, on development of sodium retention and functional and structural changes in the thick ascending limb of Henle's loop (TAL) in rats with cirrhosis induced by common bile duct ligation (CBL). CBL and sham-operated control rats were treated with octreotide-LAR (10 mg/kg body weight subcutaneously, as a single dose) or vehicle at the time of CBL or sham-CBL. The rats were instrumented with chronic catheters, and sodium balance and renal function were examined 4 weeks after CBL or sham operation. Octreotide-LAR treatment significantly inhibited sodium retention in CBL rats and prevented renal vasodilatation without changes in glomerular filtration rate (GFR). The natriuretic response to a test dose of furosemide (7.5 mg/kg body weight intravenously) was significantly increased in CBL rats, and when expressed in terms of natriuretic efficiency (mmol Na/mg furosemide in urine), the natriuretic response was increased by 57% relative to sham-operated controls. Stereological examination of kidneys demonstrated a 53% increase in the volume of the inner stripe of the outer medulla and a 108% increase in the volume of TAL epithelium in cirrhotic rats relative to controls. The increased natriuretic efficiency of furosemide as well as the hypertrophy of the inner stripe and the TAL in this renal zone were absent in CBL rats treated with octreotide-LAR. These results suggest that octreotide-LAR treatment inhibits sodium retention in cirrhotic rats, partly by inhibition of increased furosemide-sensitive sodium reabsorption in the TAL.

A sensitive, selective and efficient reversed-phase high-performance liquid chromatographic (HPLC) method is reported for the determination of furosemide in human plasma and urine. The method has a sensitivity limit of 5 ng/ml in plasma, with acceptable within- and between-day reproducibilities and good linearity (r2>0.99) over a concentration range from 0.05 to 2.00 microg/ml. The one-step extract of furosemide and the internal standard (warfarin) from acidified plasma or urine was eluted through a muBondapak C18 column with a mobile phase composed of 0.01 M potassium dihydrogenphosphate and acetonitrile (62:38, v/v) adjusted to pH 3.0. Within-day coefficients of variation (C.V.s) ranged from 1.08 to 8.63% for plasma and from 2.52 to 3.10% for urine, whereas between-day C.V.s ranged from 4.25 to 10.77% for plasma and from 5.15 to 6.81% for urine at three different concentrations. The minimum quantifiable concentration of furosemide was determined to be 5 ng/ml. The HPLC method described has the capability of rapid and reproducible measurement of low levels of furosemide in small amounts of plasma and urine. This method was utilized in bioavailability/pharmacokinetic studies for the routine monitoring of furosemide levels in adults, children and neonate patients.

The following possible explanations for the significant increases in the oral bioavailability and the diuretic and natriuretic effects of orally administered furosemide observed when ascorbic acid was coadministered to dogs were investigated: ascorbic acid might enhance the gastrointestinal (GI) absorption of furosemide, might inhibit GI wall metabolism of furosemide, might enhance the reabsorption of furosemide from the renal tubules, and might increase the unionized fraction of furosemide at the receptor sites. The significant increase in the oral bioavailability with coadministration of ascorbic acid seemed to result from reduced gastric first-pass metabolism of furosemide and not enhanced GI absorption of furosemide. This might be supported by rat studies; the percentages of the oral doses of furosemide recovered from the GI tract at 8 hr after oral administration were similar (p < 0.583) without (39.5%) and with (44.7%) coadministration of ascorbic acid, and the amounts of furosemide remaining per gram of stomach after 30-min incubations of 50 micrograms of furosemide with 9000g supernatant fractions of stomach homogenates were increased significantly (48.5 vs. 42.4 micrograms) by the addition of 100 micrograms of ascorbic acid. The significant increases in the diuretic and natriuretic effects of furosemide with ascorbic acid could be the result of increases in the reabsorption of furosemide from renal tubules and increases in the unionized fraction of furosemide at the renal tubular receptor sites. This was supported by 1.5-4.2-fold increases in urine output and approximately 20% decreases in the time-averaged renal clearance of furosemide when the urine pH was decreased by 1.5-2.5 units by oral administration of ammonium chloride.

Furosemide 1-O-acyl glucuronide (Fgnd) was extracted from the urine following oral administration of furosemide. The crude Fgnd was applied to micronized Amberlite XAD-2 column (2.5 cm i.d. x 90 cm length, 75-500 microns particle size). The purified Fgnd was identified by mass spectrometry and beta-glucuronidase treatment. This method was also applicable to the purification of glucuronide of tolmetin (nonsteroidal anti-inflammatory drug, NSAID), suggesting that it was applicable to the other NSAIDs, most of which were known to be metabolized to acyl-glucuronides.

Aims: Both indirect-response models and effect-compartment models are used to describe the pharmacodynamics of drugs when there is a delay in the time course of the pharmacological effect in relation to the concentration of the drug. The aim of this study was to investigate whether the time of maximum response after single-dose administration at different dose levels could be used to distinguish between these models and to select the most appropriate pharmacokinetic-pharmacodynamic model for frusemide., Methods: Three doses of frusemide, 10, 25 and 40 mg were given as rapid intravenous infusions to five healthy volunteers. Urine samples were collected for 5 h after dosing. Volume and sodium losses were isovolumetrically replaced with an intravenous rehydration fluid. Diuresis and natriuresis were modelled for all three doses simultaneously, applying both an indirect-response model and an effect-compartment model with the frusemide excretion rate as the pharmacokinetic input., Results: The observed time of maximum diuretic and natriuretic response significantly increased with dose. This increase was well predicted by the indirect-response model, whereas the modelling with the effect-compartment model led to a poor prediction of the peaks. There was no difference between the observed and predicted time of maximum diuretic and natriuretic response using the indirect-response model, whereas the time of maximum response predicted by the effect-compartment model was significantly earlier than the time observed for the 25 mg (P < 0.05) and 40 mg (P < 0.05) doses., Conclusions: The time of maximum response to frusemide was better described using an indirect-response model than an effect-compartment model. Studying the time of maximum response after administration of different single doses of a drug may be used as a selective tool during pharmacokinetic-pharmacodynamic modelling.

1. The aim of this study was to investigate the autoregulation of renal blood flow under physiological conditions, when challenged by the normal pressure fluctuations, and the contribution of the tubuloglomerular feedback (TGF). 2. The transfer function between 0.0018 and 0.5 Hz was calculated from the spontaneous fluctuations in renal arterial blood pressure (RABP) and renal blood flow (RBF) in conscious resting dogs. The response of RBF to stepwise artificially induced reductions in RABP was also studied (stepwise autoregulation). 3. Under control conditions (n = 12 dogs), the gain of the transfer function started to decrease, indicating improving autoregulation, below 0.06-0.15 Hz (t = 7-17 s). At 0.027 Hz a prominent peak of high gain was found. Below 0.01 Hz (t > 100 s), the gain reached a minimum (maximal autoregulation) of -6.3 +/- 0.6 dB. The stepwise autoregulation (n = 4) was much stronger (-19.5 dB). The time delay of the transfer function was remarkably constant from 0.03 to 0.08 Hz (high frequency (HF) range) at 1.7s and from 0.0034 to 0.01 Hz (low frequency) (LF) range) at 14.3 s, respectively. 4. Nifedipine, infused into the renal artery, abolished the stepwise autoregulation (-2.0 +/- 1.1 dB, n = 3). The gain of the transfer function (n = 4) remained high down to 0.0034 Hz; in the LF range it was higher than in the control (0.3 +/- 1.0 dB, P < 0.05). The time delay in the HF range was reduced to 0.5 s (P < 0.05). 5. After ganglionic blockade (n = 7) no major changes in the transfer function were observed. 6. Under furosemide (frusemide) (40 mg + 10 MG h-1 or 300 mg + 300 mg h-1 i.v..) the stepwise autoregulation was impaired to -7.8 +/- 0.3 or 6.7 +/- 1.9 dB, respectively (n = 4). In the transfer function (n = 7 or n = 4) the peak at 0.027 Hz was abolished. The delay in the LF range was reduced to -1.1 or -1.6 s, respectively. The transfer gain in the LF range (-5.5 +/- 1.2 or -3.8 +/- 0.8 dB, respectively) did not differ from the control but was smaller than that under nifedipine (P < 0.05). 7. It is concluded that the ample capacity for regulation of RBF is only partially employed under physiological conditions. The abolition by nifedipine and the negligible effect of ganglionic blockade show that above 0.0034 Hz it is almost exclusively due to autoregulation by the kidney itself. TGF contributes to the maximum autoregulatory capacity, but it is not required for the level of autoregulation expended under physiological conditions. Around 0.027 Hz, TGF even reduces the degree of autoregulation.