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Background An echocardiography-derived calcium score (ECS) has been shown to predict CV mortality in the general population but has not been utilized in the dialysis population. Methods We conducted a prospective cohort study including 125 prevalent PD patients. Two blinded and independent echocardiographers determined the ECS for each subject at baseline. The primary outcome was the three-point major adverse cardiovascular events (MACE) which is a composite outcome comprising CV Death, non-fatal myocardial infarction and non-fatal stroke. The secondary outcome was all-cause mortality. Results The mean age was 61 ± 13 years. The median follow-up duration was 40 months (range 1-50). Diabetes mellitus (DM) occurred in 76 (60.8%) of the subjects. The median duration of dialysis was 32 (IQR 16-54) months. The incidences of MACE and all-cause mortality were 13.0 per 100 patient-years and 18.3 per 100 patient-years. Multivariate Cox regression analysis identified the following 3 independent predictors of MACE: ECS (HR 1.253 / unit increase in ECS, 95% CI 1.014-1.547, p = 0.036), DM (HR 2.467, 95% CI 1.014-6.005, p = 0.047) and pre-existing CVD (HR 2.441, 95% CI 1.261-4.728, p = 0.008); and the following 2 predictors of all-cause mortality: pre-existing CVD (HR 2.156, 95% CI 1.251-3.714, p = 0.006) and serum albumin (HR 0.887 / g/L increase in serum albumin, 95% CI 0.839-0.937, p Conclusion The ECS appears to be a significant predictor of MACE in PD patients independently of DM and pre-existing CVD. This article is protected by copyright. All rights reserved.

In addition to the observation of an increased viremia among patients with chronic hepatitis C virus (HCV) infection who undergo renal transplantation, fibrosis and necroinflammatory activity have been noted to worsen comparing pre- and post-renal transplantation liver biopsies in some of these patients. Apart from the reported reduced patient and allograft survival rates, post-transplant diabetes mellitus, de novo glomerulonephritis, and an increased overall risk of infection have been observed. However, antiviral therapy for HCV is generally considered contraindicated among patients with solid organ transplants, with the main worry being the risk of acute rejection in relation to the use of interferon. We reported the long-term outcome of four renal transplant patients with chronic HCV infection who received peginterferon-based therapy. We collected the long-term follow-up data of four patients who completed the therapy with peginterferon in combination with ribavirin. Two of them had renal impairment at baseline. With treatment, they had a significant improvement in terms of serum liver transaminase level, and two patients achieved the early virological response and the other two rapid virological response. All four patients achieved sustained virological response, with neither HCV flare up nor renal dysfunction during follow-up for a mean duration of 74.3 months after therapy. These results suggest that sustained HCV virological response may be achieved without allograft dysfunction, in selected renal transplant patients using a peginterferon-based therapy.

Background and Objectives Catheter-related infection, namely exit-site infection (ESI) and peritonitis, is a major infectious complication and remains a main cause of technique failure for patients receiving peritoneal dialysis (PD). Topical application of antibiotic cream might reduce catheter-related infection but emergence of resistant or opportunistic organisms could be a concern. Optimal topical agents and regimens remain to be determined. We did a study to examine the effect of an alternating topical antibiotic regimen in preventing catheter-related infection. Method We performed a single-center, randomized, open-label study to compare daily topical application of gentamicin cream with a gentamicin/mupirocin alternate regimen to the exit site. Patients randomized to alternating regimen were asked to have daily application of gentamicin cream in odd months and mupirocin cream in even months. Primary outcomes were ESI and peritonitis. Secondary outcomes were catheter removal or death caused by catheter-related infection. A total of 146 patients (71, gentamicin group; 75, alternating regimen group) were enrolled with a total follow-up duration of 174 and 181 patient-years for gentamicin and alternating groups, respectively. All patients were followed up until catheter removal, death, transfer to another unit, transplantation or the end of the study on March 31, 2014. There were no significant differences in the age, sex, dialysis vintage, and rate of diabetes, helper-assisted dialysis and methicillin-resistant Staphylococcus aureus (MRSA) carriage state. Results No difference was seen in the time to first ESI or peritonitis. However, the time to first gram-negative peritonitis seemed longer for the gentamicin group ( p = 0.055). The 2 groups showed a similar rate of ESI (0.17/yr vs 0.19/yr, p = 0.93) but P. aeruginosa ESI was less common in the gentamicin group (0.06/yr vs 0.11/yr, p < 0.001). There was no difference in the incidence of ESI due to non-tuberculous mycobacteria. Peritonitis rate was significantly lower in the gentamicin group (0.22/yr vs 0.32/yr, p < 0.001), with a striking decrease in gram-negative peritonitis (0.08/yr vs 0.14/yr, p < 0.001), and fungal peritonitis (0.006/yr vs 0.03/yr, p < 0.001), which was all antibiotics-related episodes with antecedent use of systemic antibiotics for the treatment of catheter-related infections. There was no significant difference in the catheter loss or death related to catheter-related infection. Conclusion Alternating gentamicin/mupirocin cream application appeared as effective as gentamicin alone in preventing ESI except for P. aeruginosa. However, it was inferior to gentamicin in the prevention of peritonitis episodes, especially for those caused by gram-negative organisms. It was also not useful in reducing catheter-related infection due to opportunistic organisms but instead associated with a higher incidence of antibiotic-related fungal peritonitis.

Background Hungry bone syndrome (HBS) is an important postoperative complication after parathyroidectomy for severe secondary hyperparathyroidism (SHPT). There is, however, little data in the literature on its detailed clinical course, and the associated risk factors remain controversial. Methods We did a single-center retrospective study on 62 consecutive dialysis patients who underwent total parathyroidectomy for SHPT to examine the risk factors, clinical course and outcome. Data on demographic characteristics, perioperative laboratory parameters including serum calcium, phosphate, alkaline phosphatase (ALP) and parathyroid hormone (PTH), drug treatment for SHPT and operative details of parathyroidectomy were collected. Results Seventeen (27.4%) patients developed severe postoperative hypocalcemia with HBS. The serum calcium dropped progressively while serum ALP rose after operation until 2 weeks later when serum calcium reached the trough and serum ALP peaked. Serum phosphate also fell but stabilized between 4 and 14 days. The total postoperative calcium and vitamin D supplementation was significantly larger, and hospital stay was significantly longer in the group with HBS as compared with those without HBS. Young age, high body weight, high preoperative ALP level, and low preoperative calcium level independently predicted the development of HBS while preoperative PTH and use of cinacalcet or paricalcitol did not. Conclusion HBS was common after total parathyroidectomy in patients with SHPT, and it is important to closely monitor the postoperative serum calcium, phosphate and ALP levels in the following 2 weeks, especially for those at risk. The implications of our findings on perioperative management are discussed.

We report 9 cases of exit-site infection and continuous ambulatory peritoneal dialysis peritonitis associated with atypical mycobacteria. All patients had been using topical gentamicin cream as prophylaxis for exit-site infection before the onset of these infections. Gentamicin cream is postulated to be a potential risk factor for atypical mycobacterial infection because of selective pressure on other micro-organisms. The microbiology of atypical mycobacteria and the treatment for atypical mycobacterial infections are discussed.

Losartan, a selective angiotensin II (AT1) receptor antagonist for hypertension, is metabolized to an active carboxylic acid metabolite, E-3174, which has a longer half-life. To investigate the effects of induction of cytochrome P450 on the metabolism of losartan, we evaluated the effects of phenobarbital on the plasma profiles of losartan and E-3174 in 15 healthy male subjects. Ten subjects received a single 100 mg oral dose of losartan before and during phenobarbital administration (100 mg/day for 16 days), and five subjects received losartan before and during placebo. Urinary excretion of 6-beta-hydroxycortisol (relative to 17-hydroxycorticosteroids) was measured as an endogenous marker of cytochrome P450 induction. The geometric mean area under the plasma concentration-time curve ratios (with/without phenobarbital and 90% confidence intervals) for losartan and its metabolite (E-3174) were 0.795 (0.723, 0.875) and 0.799 (0.778, 0.820), respectively, indicating that phenobarbital treatment significantly but to a clinically minor extent reduced plasma concentrations of losartan and E-3174 (p

The pharmacokinetics of the angiotensin II receptor antagonist losartan potassium and its active carboxylic acid metabolite EXP3174 were characterized in 18 healthy male subjects after administration of intravenous losartan, intravenous EXP3174, and oral losartan. In these subjects, the average plasma clearance of losartan was 610 ml/min, and the volume of distribution was 34 L. Renal clearance (70 ml/min) accounted for 12% of plasma clearance. Terminal half-life was 2.1 hours. In contrast, the average plasma clearance of EXP3174 was 47 ml/min, and its volume of distribution was 10 L. Renal clearance was 26 ml/min, which accounted for 55% of plasma clearance; terminal half-life was 6.3 hours. After oral administration of losartan, peak concentrations of losartan were reached in 1 hour. Peak concentrations of EXP3174 were reached in 3 1/2 hours. The area under the plasma concentration-time curve of EXP3174 was about four times that of losartan. The oral bioavailability of losartan tablets was 33%. The low bioavailability was mainly attributable to first-pass metabolism. After intravenous or oral administration of losartan the conversion of losartan to the metabolite EXP3174 was 14%.

P in the do Tirofiban And Reopro Give similar Efficacy outcomes Trial (TARGET) treated with abciximab compared with tirofiban had a lower 30-day incidence of the combined end point of death, myocardial infarction, and target vessel revascularization that reflected, in large part, a decrease in the incidence of periprocedural myocardial infarction.1 We have found that the extent of platelet aggregation inhibition was greater from 15 to 60 minutes after abciximab than that after the TARGET study dosage of tirofiban (10 g/kg bolus, followed by a 0.15 g/ kg/min infusion).2–4 To identify a bolus associated with maximal inhibition of platelet aggregation, we used flow cytometry to characterize the inhibitory effects of tirofiban in blood from patients with acute coronary syndromes. In subsequent studies, the average extent of inhibition of turbidometric aggregation in response to 20 M of adenosine diphosphate (ADP) was found to be 90% during the first hour when a bolus of 25 g/kg was combined with the same infusion (0.15 g/kg/min for 18 to 24 hours) employed in the TARGET study.5 In this report, we describe the concentrations of tirofiban in blood and their correlation with the inhibition of turbidometric aggregation in response to 20 M of ADP. • • • Protocols were approved by the institutional review boards of the participating institutions. All patients provided written informed consent. Eligible patients included those with an acute coronary syndrome (ischemic symptoms plus either 0.5 mm of ST-segment depression on electrocardiogram or increased troponin or creatine kinase-MB) in whom a percutaneous coronary intervention was clinically mandated and performed. Exclusion criteria included treatment with antiplatelet agents other than aspirin in the previous 14 days, thrombolytic therapy within 24 hours, renal insufficiency (creatinine 2.5 mg/dl), and contraindication to treatment with a glycoprotein IIb/IIIa inhibitor. To perform in vitro studies, blood was obtained from patients with acute coronary syndromes before coronary intervention or treatment with an antiplatelet agent other than aspirin. After anticoagulation with corn trypsin inhibitor, a specific inhibitor of coagulation factor XIIa,6 the blood was spiked with 0, 50, 100, or 150 ng/ml of tirofiban. After incubation for 15 minutes at room temperature, the capacity to bind fibrinogen in response to 1 M of ADP was determined with the use of flow cytometry. The concentration of tirofiban in blood and its associated inhibition of platelet function were assessed in a preliminary study in which patients were treated with a 10 g/kg bolus2 and in a subsequent study in which patients were treated in a sequential, open-label, nonrandomized fashion with a 20 or 25 g/kg bolus.5 Tirofiban was administered before the start of the coronary intervention, and each bolus was combined with an 18to 24-hour infusion of 0.15 g/kg/min. Patients were treated with aspirin (325 mg before the procedure and daily) and unfractionated heparin (target activated clotting time 250 seconds). Clopidogrel (300 mg initially and then 75 mg daily) was begun after the coronary intervention ( 1 hour). The concentration of tirofiban was determined by radioimmunoassay after 5, 15, 30, 45, 60, 120, and 360 minutes.7 Platelet function was assessed by light transmission aggregometry (Bio Data Corp., Helena Laboratories, Horsham, Pennsylvania), and flow cytometry before treatment and after 15, 30, 45, 60, and 120 minutes, and an additional assessment was made after 5 minutes with flow cytometry. Blood for aggregometry was anticoagulated with D-Phe-Pro-Argchloromethyl ketone (PPACK, 38 M) to avoid effects of citrate on inhibitory properties of tirofiban.8 Blood for flow cytometry was anticoagulated with corn trypsin inhibitor. Maximal turbidometric ex vivo aggregation after 4 minutes was assessed in plateletrich plasma in response to 20 M of ADP (Chronolog, Havertown, Pennsylvania). Assessment of the capacity of platelets to bind fibrinogen was performed as previously described in detail.9 Assay and fixation were performed at each site for flow cytometry. Samples were analyzed at the University of Vermont within 30 hours. As previously described,5 the primary objective was to identify a bolus dose of tirofiban that achieved a mean inhibition of platelet aggregation of 90% plus a lower bound of the 95% confidence interval of inhibition of 85% from 15 to 45 minutes after onset of treatment. The slope of the association between selected concentrations of tirofiban and the extent of From the University of Vermont, Burlington, Vermont; University of Pennsylvania Medical Center, Philadelphia, Pennsylvania; Baylor College of Medicine, Houston, Texas; Prairie Cardiovascular, Springfield, Illinois; and Merck & Company, Inc., West Point, Pennsylvania. This report was supported by Merck & Company, Inc., West Point, Pennsylvania. Dr. Schneider’s address is: University of Vermont, 208 South Park Drive, Suite 2, Colchester, Vermont 05446. E-mail: djschnei@zoo.uvm.edu. Manuscript received August 7, 2002; revised manuscript received and accepted September 24, 2002.

Losartan is an orally active, nonpeptide angiotensin II (Ang II) (site-1) receptor antagonist. We conducted a multiple-dose study in healthy male volunteers to investigate the tolerability, blood pressure effects, and changes in plasma renin activity (PRA) and plasma Ang II concentration associated with once-daily administration of 100 mg losartan for a week. Subjects were studied on a standardized sodium diet (24-hour urinary sodium excretion, 98 +/- 37 [SD] mEq per 24 hours on the placebo run-in day). Measurements of blood pressure, heart rate, PRA, Ang II, and aldosterone were taken during a placebo run-in day and after single and multiple (7 days) daily doses of losartan (100 mg, n = 10) or placebo (n = 4). Ang II was measured specifically by high performance liquid chromatography coupled with radioimmunoassay. In subjects given losartan, respective decreases (systolic/diastolic) from run-in in supine blood pressure 6 hours after dosing were (mean +/- SD), compared with the placebo run-in day, first dose: -8.8 +/- 9.6/-6.8 +/- 5.0, last dose: -11.6 +/- 8.9/-7.0 +/- 4.8 mm Hg (p < 0.05 for all changes). At this 6-hour time point, corresponding increases from run-in in PRA were from 1.2 +/- 0.6 to 12.0 +/- 6.3 (first dose) and 9.6 +/- 4.9 (last dose) ng angiotensin I per milliliter per hour and in Ang II were from 4.3 +/- 1.7 to 72.4 +/- 33.3 and 45.7 +/- 14.1 pg/mL. All changes in PRA and Ang II were statistically significant within the losartan-treated group, and the biochemical changes were significantly greater than those in the placebo-treated group. The increment in Ang II was less after the last dose than after the first (p < 0.05). The drug was well tolerated by all subjects. These data indicate that, under the conditions of this study, losartan administration (100 mg/day for eight doses over 9 days) results in treatment-related decreases in blood pressure and increases in PRA and Ang II octapeptide.

SUMMARY: Background: The ideal treatment of lupus nephritis has yet to be defined. Both cyclophosphamide and mycophenolate mofetil have been used with encouraging results, but adverse events are frequently seen. There are no data on the use of enteric-coated mycophenolate sodium. Methods: We retrospectively reviewed 12 patients with active forms of lupus nephritis (1 class III, 7 class IV and 4 class V) treated with enteric-coated mycophenolate sodium combined with corticosteroids. Results: The mean age of the patients was 32.3 ± 11.2 years and the average length of follow up was 25.9 ± 8.9 months. The mean serum creatinine clearance was 93 ± 30.1 mL/min per 1.73 m2 and the mean proteinuria level was 4.5 ± 3.6 g/day. All had features that warranted aggressive treatment. Mycophenolate sodium was given for 12.9 ± 9.7 months with an averaged starting dose of 1350 ± 163 mg/day. Six patients attained complete remission and six attained partial remission with treatment. The mean interval to attain first remission (complete or partial) was 8.3 ± 5.7 weeks. At last follow up, all patients were in complete or partial remission. Apart from herpes zoster that developed in one patient, no other significant side-effects were encountered. Conclusion: Enteric-coated mycophenolate sodium was effective and well-tolerated in the treatment of active lupus nephritis.

Background Fungal peritonitis (FP) is associated with significant mortality and high risk of peritoneal failure. The optimum treatment for peritoneal dialysis (PD)-associated FP remains unclear. Since January 2000 we have been treating FP with a combination of intravenous amphotericin B and oral flucytosine, together with deferred catheter replacement. We examined the clinical course and outcome of the FP patients treated with this approach (study group). An outcome comparison was also made to an alternatively treated historic cohort (control group). Methods This was a single-center retrospective study. The clinical course and outcome of 13 consecutive episodes of FP occurring in 13 patients treated between January 2000 and April 2005 with the study approach were examined. The patients were treated with an incremental dose of intravenous amphotericin B to a target dose of 0.75 – 1 mg/kg body weight/day, and oral flucytosine 1 g/day upon a diagnosis of FP at 3.77 ± 0.93 days from presentation. Replacement of the peritoneal catheter was intended after complete clearing of effluent, after which, antifungal chemotherapy was continued for another 1 – 2 weeks. Their outcome was compared with 14 historic controls that were treated between April 1995 and December 1999. Results Mean age of the study group was 58.7 ± 13.2 years; male-to-female ratio was 2:11; 6 (46.1%) were diabetic. All FP were caused by Candida species ( C. albicans, 2; C. parapsilosis, 8; C. glabrata, 3). Two (15.4%) patients died before resolution of the peritonitis. The dialysate effluent cleared in 11 patients (84.6%) after 13.2 ± 3.3 days of treatment, but 2 patients died of acute myocardial infarction before catheter replacement. Nine patients had their catheters replaced at day 26.7 ± 7.7 of treatment; all 9 returned to PD after a total of 31 ± 12.2 days of antifungal chemotherapy. Reversible liver dysfunction was common with this regimen. When compared with the 14 cases in the historic control group ( Candida species, 13; Trichosporon, 1), who were treated with amphotericin B, fluconazole, or a combination of the two, and the majority (78.6%) of whose catheters were removed before day 10 of presentation, the study group appeared to have a lower technique failure rate (30.8% vs 78.6%, p = 0.013) and similar all-cause mortality (30.7% vs 28.5%, p = NS), FP-related mortality (15.4% vs 28.5%, p = NS), and length of hospitalization (48.5 ± 30.2 vs 57.0 ± 37.7 days, p = NS). However, a significantly earlier commencement of antifungal treatment in the study group (3.8 ± 0.9 vs 5.8 ± 2.4 days, p = 0.012) could be an important confounder of outcome. Conclusions Combination of intravenous amphotericin B and oral flucytosine with deferred catheter replacement appears to be associated with a relatively low incidence of PD technique failure, without affecting mortality in patients suffering from FP due to yeasts in this preliminary study. Nonetheless, drug-induced hepatic dysfunction was common; close monitoring during treatment is of paramount importance. The reasons accounting for the observed distinctive outcome remain unclear and further study is required to confirm the results and to investigate for the underlying mechanism.

Objective Fungal peritonitis (FP) is a serious complication of continuous ambulatory peritoneal dialysis (CAPD), being associated with significant morbidity and mortality. The role of nystatin prophylaxis during antibiotic therapy in the prevention of FP remains controversial, especially in programs with a modest or low baseline FP rate. The aim of the present study was to evaluate the effect of nystatin prophylaxis on the occurrence of FP in programs with a relatively modest baseline FP rate. Patients and Methods Incident and prevalent patients receiving CAPD between April 1995 and April 2005 at our center were included and divided into 2 groups. The control group included 320 patients (total follow-up 8875 patient-months) being treated without nystatin before October 1999; the nystatin group included 481 patients (total follow-up 13725 patient-months) being treated after October 1999. Nystatin tablets (500000 units, 4 times per day) were given orally during whatever use of antibiotics to cover the whole course of antibiotic therapy. Occurrence of FP and antibiotic-related FP (AR-FP) in patients with and without nystatin prophylaxis was compared. Results The two groups were of similar age but the nystatin group had a significantly higher percentage of diabetics. In addition, the nystatin group had a higher proportion of patients using disconnecting twin-bag exchange systems and had a significantly lower peritonitis rate compared with the control. There were 13 and 14 episodes of FP in the nystatin and control groups respectively. The fungal peritonitis rate of the nystatin group was slightly lower than that of the control group (0.011 vs 0.019 per patient-year) but it did not reach statistical significance. There was, however, a significant decrease in the incidence and proportion of AR-FP in the nystatin group compared with the control group, which persisted even after adjustment for the peritonitis rate. Kaplan–Meier analysis further demonstrated significantly better AR-FP-free survival in the nystatin group compared with the control group. No significant side effects were observed for nystatin. Subgroup analyses in patients of the 2 different connecting systems revealed a similar but nonsignificant trend toward reduction of AR-FP in patients given nystatin prophylaxis. Conclusion Oral nystatin prophylaxis might prevent the occurrence of AR-FP in CAPD patients, resulting in a trend toward reduction in the incidence of FP even in programs with a modest baseline FP rate. A large scale, prospective, randomized controlled trial is needed to further examine this issue.

The pharmacokinetics and pharmacodynamics of 7 days of treatment with losartan 50 mg/hydrochlorothiazide 12.5 mg were evaluated in 14 patients with normal renal function and in 12 patients with mild to moderate renal impairment. The efficacy of losartan 50 mg/hydrochlorothiazide 12.5 mg titrated to losartan 100 mg/hydrochlorothiazide 25 mg was examined in 32 hypertensive patients with mild to moderate renal impairment who were treated for 12 weeks. Safety was assessed in both studies by the incidence of adverse experiences. After 7 days of treatment, the AUC for losartan, E-3174, and hydrochlorothiazide was slightly higher in patients with mild to moderate renal impairment, but the reduction in blood pressure (BP) after 7 days was not different between the two groups. The final (week 12) mean reductions in trough sitting diastolic and systolic BP were 15.0 +/- 7.1 mmHg (p < 0.01) and 20.8 +/- 16.7 mmHg (p < 0.01), respectively. There were no observed increases in drug-related adverse experiences in either study. Overall, the combination of losartan/hydrochlorothiazide was effective in lowering blood pressure and was well tolerated in patients with mild to moderate renal impairment.

We investigated the tolerability and angiotensin II antagonist activity of oral DuP 532 in healthy male subjects. DuP 532 (1 to 200 mg) was well tolerated, with no effect on blood pressure or heart rate. Compared with losartan (100 mg), DuP 532 (200 mg) was a weak antagonist of pressor responses to intravenous angiotensin II. Maximum inhibition of diastolic pressor response was 86% (95% confidence interval [CI], 84%, 88%) approximately 4.6 hours after losartan and 48% (95% CI, 38%, 56%) 8.7 hours after DuP 532. Twenty-four hours after dosing, inhibition by losartan and DuP 532 was similar (40% to 45%). DUP 532 is extensively bound in human plasma, with an in vitro free fraction of 0.06. Although DuP 532 and EXP3174 (losartan's active metabolite) have similar AT1-receptor potency, and plasma concentrations of DuP 532 were much greater than losartan/EXP3174, the level of antagonism was much less for DuP 532. These results indicate that multiple factors determine the in vivo potency of angiotensin II antagonists, including affinity for and distribution to the receptor as modulated by plasma binding.

This was a 2-period randomized, crossover study in 8 healthy males to determine the effects of cimetidine (400 mg q.i.d. for 6 days) on the pharmacokinetics and pharmacodynamic effects of the angiotensin II receptor antagonist, losartan (100 mg). Cimetidine increased the AUC for losartan 18% without affecting the AUC for E-3174, the active metabolite of losartan. The increase in plasma renin activity following losartan was not affected by cimetidine (maximum mean increases 12.6 and 12.1 ng Ang I.ml-1.h-1 without and with cimetidine, respectively). These results indicate that cimetidine does not appear to alter the pharmacokinetics or pharmacodynamics of losartan to a clinically significant extent.

Abstract We investigated the effects of angiotensin II (Ang II) type 1 receptor blockade with losartan on the renin-angiotensin-aldosterone system in hypertensive patients (supine diastolic blood pressure, 95 to 110 mm Hg). Qualifying patients (n=51) were allocated to placebo, 25 or 100 mg losartan, or 20 mg enalapril. Blood pressure, plasma drug concentrations, and renin-angiotensin-aldosterone system mediators were measured on 4 inpatient days: end of placebo run-in, after first dose, and 2 and 6 weeks of treatment. Plasma drug concentrations were similar after the first and last doses of losartan. At 6 weeks, 100 mg losartan and 20 mg enalapril showed comparable antihypertensive activity. Four hours after dosing, compared with the run-in day, 100 mg losartan increased plasma renin activity 1.7-fold and Ang II 2.5-fold, whereas enalapril increased plasma renin activity 2.8-fold and decreased Ang II 77%. Both drugs decreased plasma aldosterone concentration. For losartan, plasma renin activity and Ang II increases were greater at 2 than at 6 weeks. Effects of losartan were dose related. After the last dose of losartan, plasma renin activity and Ang II changes were similar to placebo changes by 36 hours. These results indicate that long-term blockade of the feedback Ang II receptor in hypertensive patients produces modest increases of plasma renin activity and Ang II that do not appear to affect the antihypertensive response to the antagonist.

The formation of four major metabolites of propranolol by the liver was examined at steady state in three dogs that had undergone surgical portacaval transposition, following which injection of drug into the hindlimb delivers the total dose to the liver. Propranolol was infused directly into the liver via a hindlimb vein at dose rates ranging from 1.01 to 6.3 mg/min. In all dogs the formation of 4-hydroxypropranolol, alpha-naphthoxylactic acid, and propranolol glycol was saturable. Vmax and Km values were determined at steady state by relating the rate of excretion of each metabolite into bile and urine to the blood concentration of propranolol. The formation of propranolol glucuronide was a first order process. The use of a dog with a portacaval transposition has permitted development of a method to estimate, in vivo, the kinetic properties of enzymes responsible for hepatic first-pass metabolism of drugs.