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Recent CYP2D6 phenotype standardization efforts by CYP2D6 activity score (AS) are based on limited pharmacokinetic (PK) and pharmacodynamic (PD) data. Using data from two independent clinical trials of metoprolol, we compared metoprolol PK and PD across CYP2D6 AS with the goal of determining whether the PK and PD data support the new phenotype classification. S‐metoprolol apparent oral clearance (CLo), adjusted for clinical factors, was correlated with CYP2D6 AS (P

Introduction In intensive care unit (ICU) patients, delirium is frequent, occurs early in ICU admission, and is associated with poor outcomes. Risk models based on clinical factors have shown variable performance in terms of predictive ability. Identification of a candidate biomarker that associates with delirium may lead to a better understanding of disease mechanism, validation biomarker studies, and the ability to develop targeted interventions for prevention and treatment of delirium. This study analyzed metabolite concentrations early in the course of ICU admission to assess the association with delirium onset. Methods Within 24 hours of ICU admission, blood samples for global and targeted metabolomics analyses in adult surgical ICU patients were collected prospectively. Metabolites were determined using mass spectrometry/ultra-high-pressure liquid chromatography and analyzed in patients with delirium and a group of controls matched on age, sex, and admission Sequential Organ Function Assessment (SOFA) score. Results Patients in the study (65 per group) were a mean age of 59 years, had a median SOFA score of 6, and were most commonly admitted to the ICU following major trauma. In the delirium group, median onset of delirium was 3 (interquartile range 1-6) days, and the most common delirium subtype was mixed (56%). Kynurenic acid was significantly increased, and tryptophan concentration was significantly decreased in the delirium group (p=0.04). The ratio of kynurenine-to-tryptophan concentration was significantly higher in the delirium group (p=0.005). Conclusions Evidence of upregulation was found in the tryptophan metabolic pathway in delirious patients because tryptophan concentrations were lower, tryptophan metabolites were higher, and the kynurenine-to-tryptophan ratio was increased. These findings suggest a role of increased inflammation and accumulation of neurotoxic metabolites in the pathogenesis of ICU delirium. Future studies should target this pathway to validate metabolites in the tryptophan pathway as risk biomarkers in patients with ICU delirium.

Pioglitazone is effective in improving insulin resistance and liver histology in patients with nonalcoholic steatohepatitis (NASH). Because dysfunctional mitochondrial metabolism is a central feature of NASH, we hypothesized that an important target of pioglitazone would be alleviating mitochondrial oxidative dysfunction. To this end, we studied hepatic mitochondrial metabolism in mice fed high-fructose high-transfat diet (TFD) supplemented with pioglitazone for 20 wk, using nuclear magnetic resonance-based 13C isotopomer analysis. Pioglitazone improved whole body and adipose insulin sensitivity in TFD-fed mice. Furthermore, pioglitazone reduced intrahepatic triglyceride content and fed plasma ketones and hepatic TCA cycle flux, anaplerosis, and pyruvate cycling in mice with NASH. This was associated with a marked reduction in most intrahepatic diacylglycerol classes and, to a lesser extent, some ceramide species (C22:1, C23:0). Considering the cross-talk between mitochondrial function and branched-chain amino acid (BCAA) metabolism, pioglitazone’s impact on plasma BCAA profile was determined in a cohort of human subjects. Pioglitazone improved the plasma BCAA concentration profile in patients with NASH. This appeared to be related to an improvement in BCAA degradation in multiple tissues. These results provide evidence that pioglitazone-induced changes in NASH are related to improvements in hepatic mitochondrial oxidative dysfunction and changes in whole body BCAA metabolism.

Incidence of venous thromboembolism (VTE) in critically ill patients remains unacceptably high despite widespread use of thromboprophylaxis. A systems biology approach may be useful in understanding disease pathology and predicting response to treatment. Metabolite profile under specific environmental conditions provides the closest link to phenotype, but the relationship between metabolomics and risk of VTE in critically ill patients is unknown. In this study, metabolomics signatures are compared in patients with and without VTE.Multicenter case-control study using prospectively collected data from the Inflammation and Host Response to Injury program, with pathway and in silico gene expression analyses.Eight level 1 US trauma centers.Critically ill adults with blunt trauma who developed VTE within the first 28 days of hospitalization compared to patients without VTE (N-VTE).None.Patients included in the study (n = 20 VTE, n = 20 N-VTE) were mean age of 34 years, injury severity score of 35, and VTE diagnosed a median of 10.5 days after admission. Global metabolomics revealed two kynurenine metabolites, N-formylkynurenine (AUC = 0.77; 95% CI: 0.59-0.89) and 5-hydroxy-N-formylkynurenine (AUC = 0.80; 95% CI:0.63-0.90) significantly discriminated VTE and N-VTE; ratio between N-formylkynurenine/5-hydroxy-N-formylkynurenine improved predictive power (AUC = 0.87; 95% CI: 0.74-0.95). In the pathway analysis, tryptophan was the only significant metabolic pathway including N-formylkynurenine and 5-hydroxy-N-formylkynurenine (p 0.001), and 8 proteins directly or indirectly interacted with these metabolites in the interaction network analysis. Of the 8 genes tested in the in silico gene expression analyses, KYNU (p 0.001), CCBL1 (p 0.001), and CCBL2 (p = 0.001) were significantly different between VTE and N-VTE, controlling for age and sex.Two novel kynurenine metabolites in the tryptophan pathway associated with hospital-acquired VTE, and 3 candidate genes were identified via pathway and interaction network analyses. Future studies are warranted to validate these findings in diverse populations using a multi-omics approach.

Milk thistle is a widely-consumed botanical used for an array of purported health benefits. The primary extract of milk thistle is termed silymarin, a complex mixture that contains a number of structurally-related flavonolignans, the flavonoid, taxifolin, and a number of other constituents. The major flavonolignans present in most extracts are silybin A, silybin B, isosilybin A and isosilybin B, silydianin, silychristin and isosilychristin. Silymarin itself has been reported to inhibit CYP2C8 activity in vitro, but the effect of the individual flavonolignans on this enzyme has not been studied. To investigate the effects of milk thistle extract and its main flavonolignans (silybin A, silybin B, isosilybin A and isosilybin B) on CYP2C8 activity at relevant concentrations, the effect of milk thistle extract and the flavonolignans on CYP2C8 enzyme activity was studied in vitro using human liver microsomes (HLM) incorporating an enzyme-selective substrate for CYP2C8, amodiaquine. Metabolite formation was analyzed using liquid chromatography-tandem mass spectrometry (LC/MS-MS). The concentration causing 50% inhibition of enzyme activity (IC50) was used to express the degree of inhibition. Isosilibinin, a mixture of the diastereoisomers isosilybin A and isosilybin B, was found to be the most potent inhibitor, followed by isosilybin B with IC50 values (mean ± SE) of 1.64 ± 0.66 μg/mL and 2.67 ± 1.18 μg/mL, respectively. The rank order of observed inhibitory potency after isosilibinin was silibinin > isosilybin A > silybin A > milk thistle extract > and silybin B. These in vitro results suggest a potentially significant inhibitory effect of isosilibinin and isosilybin B on CYP2C8 activity. However, the observed IC50 values are unlikely to be achieved in humans supplemented with orally administered milk thistle extracts due to the poor bioavailability of flavonolignans documented with most commercially available formulations.

SummaryBackground Pioglitazone is a safe and effective option to manage patients with type 2 diabetes and nonalcoholic steatohepatitis (NASH). However, there is marked variability in treatment response. Aim To evaluate the relationship between concentrations of pioglitazone and its active metabolites and treatment outcomes in patients with NASH. Methods Pioglitazone concentrations were measured in patients with NASH treated with pioglitazone 45 mg/day for 18 months; liver biopsy samples were obtained at baseline and after treatment. The primary outcome was a ≥2-point reduction in NAFLD activity score (NAS) with at least one-point improvement in more than one liver histology category and without worsening of fibrosis. A novel marker, the pioglitazone exposure index, was calculated to consider the concentrations of pioglitazone as well as the two active metabolites. Results The response to pioglitazone was concentration-dependent as evidenced by the significant relationship between both pioglitazone concentration and pioglitazone exposure index with changes in NAS (r=.48, P=.0002 and r=.51, P

The emerging use of genomic data to inform medication therapy populates the medical literature and provides evidence for guidelines in the prescribing information for many medications. Despite the availability of pharmacogenomic studies, few pharmacists feel competent to use these new data in patient care. The first pharmacogenomics competency statement for pharmacists was published in 2002. In 2011, the Pharmacogenomics Special Interest Group of the American Association of Colleges of Pharmacy led a process to update this competency statement with the use of a consensus-based method that incorporated input from multiple key professional pharmacy organizations to reflect growth in genomic science as well as the need for pharmacist application of genomic data. Given the rapidly evolving science, educational needs, and practice models in this area, a standardized competency-based approach to pharmacist education and training in pharmacogenomics is needed to equip pharmacists for leadership roles as essential members of health care teams that implement clinical utilization strategies for genomic data.

The objectives of this study were to investigate the effect of grapefruit juice low in furanocoumarins on CYP3A activity and to summarize previous findings of enzyme inhibition measured by the metabolism of midazolam after intake of grapefruit juice. Twelve healthy volunteers participated in a prospective, randomized, double-blinded, 3-way crossover clinical study to determine the effect of regular grapefruit juice (RGJ) and a novel, low-furanocoumarin hybrid grapefruit juice (HGJ) on the metabolism of oral midazolam, used as a probe for in vivo CYP3A activity, compared with water as a control. The RGJ was 100% hand-squeezed "Hudson" grapefruit juice, and the HGJ contained low amounts of furanocoumarin constituents. The point estimates (90% confidence intervals) for the RGJ/water midazolam AUC geometric mean ratio was 122% (107-140). The point estimate for the HGJ/water midazolam AUC ratio was within the 80% to 125% bioequivalence range, indicating an absence of interaction. This finding also prompted a systematic review of available evidence on the pharmacokinetic alteration of midazolam by grapefruit juice. Although most studies demonstrated alteration in midazolam pharmacokinetics supporting inhibition of CYP3A activity as a likely mechanism, the cohorts included in these studies and the extent of the pharmacokinetic interaction varied widely. The current study indicated grapefruit juice-drug interaction varies substantially based on patient characteristics and/or grapefruit juice product-related factors, including the amount of furanocoumarin constituents present in the juice.

Beverage-drug interactions have remained an active area of research and have been the subject of extensive investigations in the past 2 decades. The known mechanisms of clinically relevant beverage-drug interactions include modulation of the activity of cytochrome P450 (CYP) 3A and organic anion-transporting polypeptide (OATP). For CYP3A-mediated beverage-drug interaction, the in vivo CYP3A inhibitory effect is limited to grapefruit juice (GFJ), which increases the bioavailability of several orally administered drugs that undergo extensive first-pass metabolism via enteric CYP3A. In contrast, clinically significant OATP-mediated beverage-drug interactions have been observed with not only GFJ but also orange juice, apple juice, and, most recently, green tea. Fruit juices and green tea are all a mixture of a large number of constituents. The investigation of specific constituent(s) responsible for the enzyme and/or transporter inhibition remains an active area of research, and many new findings have been obtained on this subject in the past several years. This review highlights the multiple mechanisms through which beverages can alter drug disposition and provides an update on the new findings of beverage-drug interactions, with a focus on fruit juices and green tea.

Background Although hydrochlorothiazide ( HCTZ ) is a well‐established first‐line antihypertensive in the United States, HCTZ treated patients achieve blood pressure ( BP ) control. Thus, identifying biomarkers that could predict the BP response to HCTZ is critically important. In this study, we utilized metabolomics, genomics, and lipidomics to identify novel pathways and biomarkers associated with HCTZ BP response. Methods and Results First, we conducted a pathway analysis for 13 metabolites we recently identified to be significantly associated with HCTZ BP response. From this analysis, we found the sphingolipid metabolic pathway as the most significant pathway ( P =5.8E‐05). Testing 78 variants, within 14 genes involved in the sphingolipid metabolic canonical pathway, with the BP response to HCTZ identified variant rs6078905, within the SPTLC 3 gene, as a novel biomarker significantly associated with the BP response to HCTZ in whites (n=228). We found that rs6078905 C‐allele carriers had a better BP response to HCTZ versus noncarriers (∆ SBP /∆ DBP : −11.4/−6.9 versus −6.8/−3.5 mm Hg; ∆ SBP P =6.7E‐04; ∆ DBP P =4.8E‐04). Additionally, in blacks (n=148), we found genetic signals in the SPTLC 3 genomic region significantly associated with the BP response to HCTZ ( P HCTZ DBP ‐response ( r =−0.42; P =7E‐03) and SBP ‐response ( r =−0.36; P =2E‐02). Conclusions This study provides insight into potential pharmacometabolomic and genetic mechanisms underlying HCTZ BP response and suggests that SPTLC 3 is a potential determinant of the BP response to HCTZ . Clinical Trial Registration URL : http://www.clinicaltrials.gov . Unique identifier: NCT 00246519.

A simple and rapid high performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the simultaneous determination of pioglitazone and its active metabolites hydroxypioglitazone and ketopioglitazone in human plasma. Samples were processed by protein precipitation with acetonitrile and selective phospholipid depletion in a 96-well plate format. The method used deuterated internal standards for each analyte. Chromatographic separation was achieved with gradient elution on a Hypersil GOLD C18 column. The mass spectrometer was operated in electrospray positive ion mode with detection by selected reaction monitoring using the transitions m/z 357.1>134.0 for pioglitazone, m/z 373.1>150.0 for hydroxypioglitazone, and m/z 371.0>148.0 for ketopioglitazone. A linear standard curve was established for the range of 10-1800ng/mL for all three analytes. Intra-run and inter-run precision and accuracy (relative error) were less than 15%, and the mean extraction recoveries of all analytes were more than 87.8%. The validated method is sensitive and selective and was successfully applied to analyze clinical samples obtained from patients with nonalcoholic fatty liver disease taking pioglitazone.

Background— The 5-amino acid (AA) signature, including isoleucine, leucine, valine, tyrosine, and phenylalanine, has been associated with incident diabetes mellitus and insulin resistance. We investigated whether this same AA signature, single-nucleotide polymorphisms in genes in their catabolic pathway, was associated with development of impaired fasting glucose (IFG) after atenolol treatment. Methods and Results— Among 234 European American participants enrolled in the Pharmacogenomic Evaluation of Antihypertensive Responses (PEAR) study and treated with atenolol for 9 weeks, we prospectively followed a nested cohort that had both metabolomics profiling and genotype data available for the development of IFG. We assessed the association between baseline circulating levels of isoleucine, leucine, valine, tyrosine, and phenylalanine, as well as single-nucleotide polymorphisms in branched-chain amino-acid transaminase 1 (BCAT1) and phenylalanine hydroxylase (PAH ) with development of IFG. All baseline AA levels were strongly associated with IFG development. Each increment in standard deviation of the 5 AAs was associated with the following odds ratio and 95% confidence interval for IFG based on a fully adjusted model: isoleucine 2.29 (1.31–4.01), leucine 1.80 (1.10–2.96), valine 1.77 (1.07–2.92), tyrosine 2.13 (1.20–3.78), and phenylalanine 2.04 (1.16–3.59). The composite P value was 2×10 −5 . Those with PAH (rs2245360) AA genotype had the highest incidence of IFG ( P for trend=0.0003). Conclusions— Our data provide important insight into the metabolic and genetic mechanisms underlying atenolol-associated adverse metabolic effects. Clinical Trial Registration— http://www.clinicaltrials.gov ; Unique Identifier: NCT00246519

The xanthones α-mangostin and γ-mangostin are the major bioactive compounds in Garcinia mangostana (mangosteen) fruit extracts. Previously, we reported the pharmacokinetic properties of α-mangostin in rats. The purpose of this follow-up study was to compare the pharmacokinetic characteristics of α-mangostin and γ-mangostin in rats if administered as either a pure compound or as a component of a mangosteen fruit extract. The absolute bioavailability of γ-mangostin when administered as a pure compound was determined by giving male Sprague Dawley rats 2 mg/kg γ-mangostin intravenously or 20 mg/kg orally. A 160 mg/kg aliquot of mangosteen fruit extract was administered, containing α- and γ-mangostin doses equal to 20 mg/kg and 4.5 mg/kg of each pure compound, respectively. Plasma samples were collected for both pharmacokinetic studies, and compound concentrations were measured by LC-MS/MS. The pharmacokinetic of γ-mangostin after intravenous administration followed a two-compartment body model. The half-life of the distribution phase was 2.40 min, and that of the elimination phase was 1.52 h. After oral administration, both α- and γ-mangostin underwent intensive first-pass metabolism, and both compounds were conjugated rapidly after oral administration. When given as an extract, the total absorption of α- and γ-mangostin was not increased, but the conjugation was slower, resulting in increased free (unconjugated) compound exposure when compared to pure compound administration. Since reported beneficial biological activities of mangosteen xanthones are based on the free, unconjugated compounds, food supplements containing mangosteen fruit extracts should be preferred over the administration of pure xanthones.

Atenolol, a commonly prescribed β blocker for hypertension, is also associated with adverse cardiometabolic effects such as hyperglycemia and dyslipidemia. Knowledge of the mechanistic underpinnings of these adverse effects of atenolol is incomplete. We sought to identify biomarkers associated with risk for these untoward effects of atenolol. We measured baseline blood serum levels of acylcarnitines (ACs) that are involved in a host of different metabolic pathways, to establish associations with adverse cardiometabolic responses after atenolol treatment. Serum samples from Caucasian hypertensive patients (n = 224) who were treated with atenolol in the Pharmacogenomic Evaluation of Antihypertensive Responses (PEAR) study were interrogated using a quantitative LC/MS assay for a large number of unique ACs in serum. For the 23 ACs that were detected in serum from ≥80 % of all patients, we conducted linear regression for changes in cardiometabolic factors with baseline AC levels, baseline cardiometabolic factors, age, sex, and BMI as covariates. For the 5 ACs that were detected in serum from 20 to 79 % of the patients, we similarly modeled changes in cardiometabolic factors, but with specifying the AC as present/absent in the regression. Among the 28 ACs, the presence (vs. absence) of arachidonoyl-carnitine (C20:4) was significantly associated with increased glucose (p = 0.0002), and was nominally associated with decreased plasma HDL-C (p = 0.017) and with less blood pressure (BP) lowering (p = 0.006 for systolic BP, p = 0.002 for diastolic BP), after adjustment. Serum level of C20:4 is a promising biomarker to predict adverse cardiometabolic responses including glucose and poor antihypertensive response to atenolol.

While atenolol is an effective antihypertensive agent, its use is also associated with adverse events including hyperglycemia and incident diabetes that may offset the benefits of blood pressure lowering. By combining metabolomic and genomic data acquired from hypertensive individuals treated with atenolol, it may be possible to better understand the pathways that most impact the development of an adverse glycemic state. To identify biomarkers that can help predict susceptibility to blood glucose excursions during exposure to atenolol. Plasma samples acquired from 234 Caucasian participants treated with atenolol in the Pharmacogenomic Evaluation of Antihypertensive Responses trial were analyzed by gas chromatography Time-Of-Flight Mass Spectroscopy. Metabolomics and genomics data were integrated by first correlating participant’s metabolomic profiles to change in glucose after treatment with atenolol, and then incorporating genotype information from genes involved in metabolite pathways associated with glucose response. Our findings indicate that the baseline level of β-alanine was associated with glucose change after treatment with atenolol (Q = 0.007, β = 2.97 mg/dL). Analysis of genomic data revealed that carriers of the G allele for SNP rs2669429 in gene DPYS, which codes for dihydropyrimidinase, an enzyme involved in β-alanine formation, had significantly higher glucose levels after treatment with atenolol when compared with non-carriers (Q = 0.05, β = 2.76 mg/dL). This finding was replicated in participants who received atenolol as an add-on therapy (P = 0.04, β = 1.86 mg/dL). These results suggest that β-alanine and rs2669429 may be predictors of atenolol-induced hyperglycemia in Caucasian individuals and further investigation is warranted.

Incidence of venous thromboembolism (VTE) in adult trauma patients is high despite mechanical and pharmacologic prophylaxis. We hypothesized that thrombin formation capacity as measured by calibrated automated thrombogram (CAT) is increased early in hospitalization and is associated with the development of VTE.We conducted a prospective study in adult, critically ill trauma patients. Plasma was generated from whole blood samples collected within the first 3days of hospital admission. CAT was used to determine lag time, thrombin peak, time to thrombin peak, endogenous thrombin potential (ETP), and velocity index in plasma samples from patients, and in control samples of platelet-poor, pooled normal plasma.There were 35 trauma patients and 35 controls included in this pilot analysis. Patients were a mean (SD) age of 45 (19) years, and 23 (66%) were male. The most common mechanism of injury was motor vehicle crash followed by falls, and the median (IQR) injury severity score was 17 (12-27). Three patients (8.6%) had deep vein thrombosis (DVT) confirmed by Doppler ultrasound on median hospital day 7. Compared to control samples, patients had significantly longer lag times (3.1min vs. 2.7min, p=0.02) and significantly higher ETP (1136nM∗min vs. 1019nM∗min, p=0.007), peak thrombin generation (239nM vs. 176nM, p0.001), and velocity index (108nM/min vs. 57nM/min, p0.001) (Fig. 1). There was no difference in the time to peak thrombin generation between the two groups (5.5min vs. 5.7min, p=0.22). In the 3 patients with VTE compared to controls, lag times were shorter and velocity index was higher while ETP and peak thrombin generation were similar. There were no statistically significant differences in thrombin generation parameters in patients with or without VTE, but lag time was numerically shorter, and thrombin peak, time to peak and area-under-the-curve (ETP) were numerically lower in patients with DVT.We observed a thrombin generation profile in critically ill trauma patients consistent with an early hypercoagulable state; however, thrombin generation parameters did not discriminate patients with VTE.

The objectives of this study were to investigate the effect of grapefruit juice low in furanocoumarins on CYP3A activity and to summarize previous findings of enzyme inhibition measured by the metabolism of midazolam after intake of grapefruit juice. Twelve healthy volunteers participated in a prospective, randomized, double-blinded, 3-way crossover clinical study to determine the effect of regular grapefruit juice (RGJ) and a novel, low-furanocoumarin hybrid grapefruit juice (HGJ) on the metabolism of oral midazolam, used as a probe for in vivo CYP3A activity, compared with water as a control. The RGJ was 100% hand-squeezed "Hudson" grapefruit juice, and the HGJ contained low amounts of furanocoumarin constituents. The point estimates (90% confidence intervals) for the RGJ/water midazolam AUC geometric mean ratio was 122% (107-140). The point estimate for the HGJ/water midazolam AUC ratio was within the 80% to 125% bioequivalence range, indicating an absence of interaction. This finding also prompted a systematic review of available evidence on the pharmacokinetic alteration of midazolam by grapefruit juice. Although most studies demonstrated alteration in midazolam pharmacokinetics supporting inhibition of CYP3A activity as a likely mechanism, the cohorts included in these studies and the extent of the pharmacokinetic interaction varied widely. The current study indicated grapefruit juice-drug interaction varies substantially based on patient characteristics and/or grapefruit juice product-related factors, including the amount of furanocoumarin constituents present in the juice.

Caffeine reduces the amount of analgesic medications necessary to provide postoperative pain (POP) relief and augments treatments for headaches and dental pain. Despite considerable evidence of its beneficial effects, little is understood about the role of dietary caffeine consumption on baseline pain sensitivity or POP following oral surgery.Baseline experimental pain testing (quantitative sensory testing [QST]) using four stimulus modalities was conducted on 30 healthy adults (53% females) before surgical extraction of four third molars. Self-reported caffeine ingestion was reported before QST, and on the day of surgery, preoperative and postoperative caffeine plasma concentrations (CPC) were measured by mass spectrometry. POP ratings were obtained at timed intervals.In QST, compared to subjects who self-reported no caffeine intake, those who self-reported caffeine ingestion demonstrated a higher pain sensitivity, particularly, on ramp and hold sustained heat at 44°C and 46°C, as well as a lower heat pain threshold and tolerance (Self-reported, dietary caffeine intake was associated with higher QST ratings with lower threshold and tolerance particularly on heat pain modalities. External factors (i.e., analgesic dosage) may have played a role in the analgesic effects of caffeine on POP in oral surgery, especially in individuals with CPC exceeding 300 ng/mL who reported lower pain.

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT • The pharmacokinetics of cyclophosphamide and 4-hydroxycyclophosphamide in cancer patients have been well described. The current study was conducted to document the pharmacokinetics of cyclophosphamide and 4-hydroxycyclophosphamide in patients with glomerulonephritis. The study was necessary due to the numerous clinical abnormalities that are present in glomerulonephritis (altered glomerular filtration rate, proteinuria, hypoalbuminaemia) which can alter the disposition of drugs. WHAT THIS STUDY ADDS • This study documents the differences in pharmacokinetics of cyclophosphamide and 4-hydroxycyclophosphamide in glomerulonephritis vs. the cancer population. The current results demonstrate that clinical and pharmacogenetic covariates can both alter the disposition of cyclophosphamide and 4-hydroxycyclophosphamide in glomerulonephritis. AIMS Cyclophosphamide, the precursor to the active 4-hydroxycyclophosphamide, is used in active glomerulonephritis despite limited pharmacokinetics data. The pharmacokinetics of cyclophosphamide and 4-hydroxycyclophosphamide were evaluated. The influence of laboratory and pharmacogenomic covariates on pharmacokinetics was evaluated as a secondary aim. METHODS Glomerulonephritis patients (n = 23) participated in a pharmacokinetic evaluation. Blood was serially collected and assayed for cyclophosphamide and 4-hydroxycyclophosphamide by LC/MS methods. Kidney function, serum albumin and polymorphisms in drug metabolism or transport genes were evaluated. Analyses included non-compartmental pharmacokinetics and parametric and non-parametric statistics. RESULTS The mean area under the plasma concentration–time curve (AUC(0,∞)) data were 110 100 ± 42 900 ng ml−1 h and 5388 ± 2841 ng ml−1 h for cyclophosphamide and 4-hydroxycyclophosphamide, respectively. The mean metabolic ratio was 0.06 ± 0.04. A statistically significant relationship was found between increased serum albumin and increased half-life (0.584, P = 0.007, 95% CI 0.176, 0.820) and a borderline relationship with AUC(0,∞) (0.402, P = 0.079, 95% CI –0.064, 0.724) for 4-hydroxycyclophosphamide. Covariate relationships that trended toward significance for cyclophosphamide included decreased serum albumin and increased elimination rate constant (–0.427, P = 0.061, 95% CI 0.738, 0.034), increased urinary protein excretion and increased AUC(0,∞) (–0.392, P = 0.064, 95% CI –0.699 to 0.037), decreased Cmax (0.367, P = 0.085, 95% CI –0.067, 0.684) and decreased plasma clearance (–0.392, P = 0.064, 95% CI –0.699, 0.037). CYP2B6*9 variants vs. wildtype were found to have decreased elimination rate constant (P = 0.0005, 95% CI 0.033, 0.103), increased Vd (P = 0.0271, 95% CI −57.5, −4.2) and decreased Cmax (P = 0.0176, 95% CI 0.696, 6179) for cyclophosphamide. ABCB1 C3435T variants had a borderline decrease in cyclophosphamide elimination rate constant (P = 0.0858; 95% CI –0.005, 0.102). CONCLUSIONS Pharmacokinetics of cyclophosphamide and 4-hydroxycyclophosphamide in patients with lupus nephritis and small vessel vasculitis are similar. Clinical and pharmacogenetic covariates alter disposition of cyclophosphamide and 4-hydroxycyclophosphamide. Clinical findings of worsened glomerulonephritis lead to increased exposure to cyclophosphamide vs. the active 4-hydroxycyclophosphamide, which could have relevance in terms of clinical efficacy. The CYP2B6*9 and ABCB1 C3435T polymorphisms alter the pharmacokinetics of cyclophosphamide and 4-hydroxycyclophosphamide in glomerulonephritis.

It is unclear whether high-fructose corn syrup (HFCS), which contains a higher amount of fructose and provides an immediate source of free fructose, induces greater systemic concentrations of fructose as compared with sucrose. It is also unclear whether exposure to higher levels of fructose leads to increased fructose-induced adverse effects. The objective was to prospectively compare the effects of HFCS- vs sucrose-sweetened soft drinks on acute metabolic and hemodynamic effects. Forty men and women consumed 24 oz of HFCS- or sucrose-sweetened beverages in a randomized crossover design study. Blood and urine samples were collected over 6 hours. Blood pressure, heart rate, fructose, and a variety of other metabolic biomarkers were measured. Fructose area under the curve and maximum concentration, dose-normalized glucose area under the curve and maximum concentration, relative bioavailability of glucose, changes in postprandial concentrations of serum uric acid, and systolic blood pressure maximum levels were higher when HFCS-sweetened beverages were consumed as compared with sucrose-sweetened beverages. Compared with sucrose, HFCS leads to greater fructose systemic exposure and significantly different acute metabolic effects.

Study Objective. To assess the effects of the cytochrome P450 (CYP) 3A genotype, CYP3A5, on atorvastatin pharmacokinetics and its interaction with clarithromycin. Design. Prospective, two-phase, randomized-sequence, open-label pharmacokinetic study. Setting. Clinical research center at a teaching hospital. Subjects. Twenty-three healthy volunteers who were screened for genotype: 10 subjects carried the CYP3A5*1 allele (expressors) and 13 subjects did not (nonexpressors). Intervention. In one phase, subjects received a single oral dose of atorvastatin 20 mg. In the other phase, subjects received clarithromycin 500 mg twice/day for 5 days; on day 4 after the morning dose, subjects also received a single oral dose of atorvastatin 20 mg. All subjects participated in both phases of the study, which were separated by at least 14 days. Measurements and Main Results. Pharmacokinetic parameters of both forms of atorvastatin-atorvastatin acid and atorvastatin lactone-were compared between CYP3A5 expressors and nonexpressors, both in the absence and presence of clarithromycin, a strong CYP3A inhibitor. The acid form is pharmacologically active, and the lactone form has been associated with the atorvastatin's muscle-related adverse effects. Atorvastatin acid exposure did not differ significantly between CYP3A5 genotype groups. When subjects had not received clarithromycin pretreatment, the area under the concentration-time curve from time zero extrapolated to infinity (AUC(0-∞)) of atorvastatin lactone was 36% higher in nonexpressors than in expressors (median 47.6 ng•hr/ml [interquartile range (IQR) 37.8-64.3 ng•hr/ml] vs 34.9 ng•hr/ml [IQR 21.6-42.2 ng•hr/ml], p=0.038). After clarithromycin pretreatment, changes in the pharmacokinetic parameters of atorvastatin acid and lactone were not significantly different between the nonexpressors versus the expressors; however, the increase in the AUC(0-∞) of atorvastatin lactone was 37% greater in expressors than in nonexpressors (geometric mean ± SD 3.59 ± 0.57 vs 2.62 ± 0.35, p=0.049). Conclusion. Our data suggest that the CYP3A5 genotype has minimal effects on the pharmacokinetic parameters of atorvastatin and its interaction with clarithromycin; these effects are unlikely to be clinically significant.

The aim of this study was to investigate the effect of commonly used botanicals on UDP-glucuronosyltransferase (UGT) 1A4, UGT1A6, and UGT1A9 activities in human liver microsomes. The extracts screened were black cohosh, cranberry, echinacea, garlic, ginkgo, ginseng, milk thistle, saw palmetto, and valerian in addition to the green tea catechin epigallocatechin gallate (EGCG). Formation of trifluoperazine glucuronide, serotonin glucuronide, and mycophenolic acid phenolic glucuronide was used as an index reaction for UGT1A4, UGT1A6, and UGT1A9 activities, respectively, in human liver microsomes. Inhibition potency was expressed as the concentration of the inhibitor at 50% activity (IC(50)) and the volume in which the dose could be diluted to generate an IC(50)-equivalent concentration [volume/dose index (VDI)]. Potential inhibitors were EGCG for UGT1A4, milk thistle for both UGT1A6 and UGT1A9, saw palmetto for UGT1A6, and cranberry for UGT1A9. EGCG inhibited UGT1A4 with an IC(50) value of (mean ± S.E.) 33.8 ± 3.1 μg/ml. Milk thistle inhibited both UGT1A6 and UGT1A9 with IC(50) values of 59.5 ± 3.6 and 33.6 ± 3.1 μg/ml, respectively. Saw palmetto and cranberry weakly inhibited UGT1A6 and UGT1A9, respectively, with IC(50) values100 μg/ml. For each inhibition, VDI was calculated to determine the potential of achieving IC(50)-equivalent concentrations in vivo. VDI values for inhibitors indicate a potential for inhibition of first-pass glucuronidation of UGT1A4, UGT1A6, and UGT1A9 substrates. These results highlight the possibility of herb-drug interactions through modulation of UGT enzyme activities. Further clinical studies are warranted to investigate the in vivo extent of the observed interactions.

The present study assessed the absolute and relative bioavailabilities of dodeca-2 E,4 E,8 Z,10 E/ Z-tetraenoic acid isobutylamides (tetraenes), the main bioactive constituents in Echinacea, administered as pure compounds or in the form of an Echinacea purpurea root extract preparation. Tetraenes were administered orally by gavage or intravenously in a dose of 0.75 mg/kg. The extract was administered orally in a dose of 158.6 mg/kg which corresponds to the same amount of tetraenes. Pharmacokinetic parameters of tetraenes were calculated by non-compartmental analysis using WinNonlin® 5.2 software. Mean dodeca-2 E,4 E,8 Z,10 E/ Z-tetraenoic acid isobutylamide dose-normalized plasma area under the concentration-time curve (AUC₀-∞/dose) was 3.24 ± 0.32 min · ng/mL/µg and 0.95 ± 0.16 min · ng/mL/µg after iv and oral administrations, respectively, and 1.53 ± 0.18 min · ng/mL/µg after oral administration of the Echinacea root extract. The absolute oral bioavailability of dodeca-2 E,4 E,8 Z,10 E/ Z-tetraenoic acid isobutylamides was 29.2 ± 2.3 %, which was increased to 47.1 ± 7.2 % (1.6-fold) by administration of the Echinacea extract. Administration of an Echinacea extract increased blood exposure with no impact on C(max), but prolonged the elimination half-life to 123.3 ± 15.7 min in comparison to 35.8 ± 6.5 min after administration of the pure dodeca-2 E,4 E,8 Z,10 E/ Z-tetraenoic acid isobutylamides.

The use of herbal supplements has increased steadily over the last decade. Recent surveys show that many people who take herbal supplements also take prescription and nonprescription drugs, increasing the risk for potential herb-drug interactions. While cytochrome P450-mediated herb-drug interactions have been extensively characterized, the effects of herbal extracts and constituents on UDP-glucuronosyl transferase (UGT) enzymes have not been adequately studied. Thus, the purpose of this review is to evaluate current evidence on the glucuronidation of phytochemicals and the potential for UGT-mediated herb-drug interactions with the top-selling herbal supplements in the United States and Europe. IN VITRO and animal studies indicate that cranberry, GINKGO BILOBA, grape seed, green tea, hawthorn, milk thistle, noni, soy, St. John's wort, and valerian are rich in phytochemicals that can modulate UGT enzymes. However, the IN VIVO consequences of these interactions are not well understood. Only three clinical studies have investigated the effects of herbal supplements on drugs cleared primarily through UGT enzymes. Evidence on the potential for commonly used herbal supplements to modulate UGT-mediated drug metabolism is summarized. Moreover, the need for further research to determine the clinical consequences of the described interactions is highlighted.

Study Objective—To evaluate whether the level of systemic exposure to atenolol explains observed interindividual differences in adverse metabolic responses. Design—Open-label, prospective, pharmacokinetic pilot substudy of the Pharmacogenomic Evaluation of Antihypertensive Responses (PEAR) study. Setting—General clinical research center. Patients—Fifteen hypertensive adults (mean age 46 ± 8.9 yrs) who were enrolled in the PEAR study. Intervention—Patients received atenolol therapy for at least 8 weeks, with 5 of those weeks at a dosage of 100 mg/day, and then underwent a 2-hour oral glucose tolerance test during a pharmacokinetic study visit. Measurements and Main Results—Twenty-hour plasma atenolol concentrations were measured during the pharmacokinetic visit. Glucose and insulin levels were measured during the 2-hour oral glucose tolerance test, and fasting plasma lipid, glucose, and insulin levels were measured at baseline and after 8 weeks of atenolol treatment. A significant association was noted between atenolol area under the concentration-time curve (AUC) and change in fasting glucose level when adjusted for covariates (p=0.0025); the effect was strongest in women. No significant relationship was noted between plasma atenolol concentration and glucose AUC during oral glucose tolerance testing (r=0.08, p=0.78), nor between atenolol AUC and change in triglyceride levels (r=0.13, p=0.63). Conclusion—Higher plasma atenolol exposure may be a risk factor for an increase in fasting plasma glucose level during atenolol treatment. These findings require confirmation in a larger sample.

Chronic kidney disease affects more than 50 million people in the U.S.1. The top three etiologies for end-stage kidney disease are diabetes mellitus (45% of patients), hypertension (29% of patients), and glomerulonephritis (19% of patients).2 While it is well established that chronic kidney diseases can result in decreased elimination of drugs via the kidneys, the effects of kidney disease on non-renal clearance processes, especially specific metabolic routes, are less well described. Experimental models of chronic kidney disease have reported reductions in hepatic cytochrome P450 (CYP) enzymes including 3A1, 3A2, 2C11, and N-acetyltransferases.3–5 Reductions in nonrenal clearance ranging from 30% to 67% have been reported for substrates of the CYP3A4, CYP2D6, CYP2B6, and CYP2C9 enzymes in patients with kidney disease.6 In order to fully understand the clinical significance of altered metabolic routes associated with kidney disease, it will be necessary to evaluate the effects that specific forms of kidney diseases have on these pathways and whether these processes effect drug disposition. Numerous studies have reported various probe drugs or cocktail approaches to evaluate the in vivo function of various drug metabolizing enzymes and transporters in patients.7, 8 However, only a few studies9–12 were actually conducted in chronic kidney disease patients, and hence applicability of most of the published studies beyond the healthy control population remains to be established. As chronic kidney disease patients are commonly prescribed ~10–12 different daily medications13, studies that evaluate metabolic pathway alterations should address requirements for modifications in drug regimens as well as drug interaction potential. While studies designed to assess and report the pharmacokinetics of bupropion exist14, 15, studies designed specifically to assess the influence of chronic kidney diseases on CYP2B6 activity are currently nonexistent. CYP2B6 is responsible for the metabolism of 3–8% of the currently marketed drugs16, 17 including bupropion, cyclophosphamide, efavirenz, selegiline, methadone, and sertraline18–22 and several drugs, including clopidrogrel, ticlopidine, clotrimazole, itraconazole, sertraline, and raloxifene have been purported to inhibit CYP2B6.23 Data from healthy subjects demonstrate that both the R and S enantiomers of bupropion and its hydroxy-metabolite are present in plasma, but only stereoselective S bupropion and (S,S) hydroxybupropion formation clearance have been shown to be a phenotypic probe for CYP2B624, complicating the assessment of in vivo activity. The purpose of the current study was to evaluate the pharmacokinetics of enantiomeric bupropion and its hydroxybupropion metabolite in patients with kidney diseases affecting the glomerulus in order to provide an assessment of CYP2B6 activity in this disease state.

Herb-drug interactions have received more attention in recent years because of the widespread popularity of herbal supplements. However, there are limited data on the effect of herbs on glucuronidation in humans. The goal of this work was to examine the effect of Ginkgo biloba extract and its main flavonoid and terpene lactone constituents on mycophenolic acid (MPA) 7-O-glucuronidation. Human liver (HLM) and intestinal (HIM) microsomes were incubated with MPA and G. biloba extract (unhydrolyzed or acid-hydrolyzed), quercetin, kaempferol, ginkgolide A, ginkgolide B, or bilobalide. MPA-7-O-glucuronide formation was inhibited in HLM and HIM incubations by unhydrolyzed [IC(50) = 84.3 (HLM) and 6.9 (HIM) microg/ml] and hydrolyzed [IC(50) = 20.9 (HLM) and 4.3 (HIM) microg/ml] G. biloba extracts, quercetin [IC(50) = 19.1 (HLM) and 5.8 (HIM) microM], and kaempferol [IC(50) = 23.1 (HLM) and 7.7 (HIM) microM]. Terpene lactones did not show inhibition of MPA glucuronidation. Quercetin was a mixed-type inhibitor in HLM and HIM incubations [K(i) = 11.3 (HLM) and 2.8 (HLM) microM], whereas kaempferol was a noncompetitive inhibitor in HLM (K(i) = 33.7 microM) and a mixed-type inhibitor in HIM (K(i) = 4.5 microM). These results indicate that G. biloba extract or quercetin- and kaempferol-rich supplements may inhibit intestinal and hepatic glucuronidation of MPA. Future studies are needed to evaluate the clinical significance of this interaction.

ESRD can affect the pharmacokinetic disposition of drugs subject to nonrenal clearance. Cytochrome P450 (CYP) enzymes, including CYP3A, and multiple intestinal and hepatic drug transporters are thought to mediate this process, but the extent to which kidney disease alters the function of these proteins in humans is unknown. We used midazolam and fexofenadine to assess CYP3A (intestinal and hepatic) and drug transport, respectively, in patients with ESRD and healthy control subjects. We evaluated the effect of uremia on CYP3A and transporter expression in vitro by incubating normal rat hepatocytes and enterocytes with serum drawn from study participants. ESRD dramatically reduced nonrenal transporter function, evidenced by a 63% decrease in clearance (P < 0.001) and a 2.8-fold increase in area under the plasma concentration–time curve for fexofenadine (P = 0.002), compared with control subjects. We did not observe significant differences in midazolam or 1′-hydroxymidazolam clearance or area under the curve after oral administration, suggesting that CYP3A function is not changed by ESRD. Changes in hepatocyte and enterocyte protein expression in the presence of uremic serum were consistent with in vivo results. These findings demonstrate a mechanism for altered drug disposition in kidney disease, which may partially account for the high rates of drug toxicity in this population.

A rapid and sensitive method for the determination of visnagin in rat plasma was developed using liquid chromatography tandem mass spectrometry (LC-MS/MS). The plasma samples were processed by protein precipitation with methanol:acetonitrile (25:75) and warfarin was used as the internal standard. After vortex mixing and centrifugation, the supernatants were diluted with water (1:5) and then directly injected onto a Phenomenex Synergi Max RP column (75 mm x 2.0 mm ID, 4 microm) with isocratic elution at a flow rate of 0.2 mL/min. The mobile phase consisted of water and methanol (15:85, v/v) containing 0.1% formic acid and 5mM ammonium acetate. The total run time (injection to injection) was less than 4 min. Detection of the analytes was achieved using positive ion electrospray in the selected reaction monitoring (SRM) mode. The linear standard curve ranged from 1.0 to 5000 ng/mL and the precision and accuracy (inter- and intra-run) were within 4.5% and 4.3%, respectively. The method, which is rapid, simple, and precise, was successfully used to support a visnagin pharmacokinetics study.

A simplified method to determine clarithromycin concentrations in human plasma using protein precipitation in a 96-well plate and liquid chromatography–tandem mass spectrometry was developed and validated. Plasma proteins were precipitated with acetonitrile and roxithromycin was used as the internal standard. After vortex mixing and centrifugation, the supernatants were directly injected onto a Phenomenex Luna Phenyl–Hexyl column (50 mm × 2.0 mm ID, 3 μm). The mobile phase consisted of water and methanol (30:70, v/v) containing 0.1% formic acid and 5 mM ammonium acetate. The flow rate was 0.22 mL/min and the total run time (injection to injection) was less than 3 min. Detection of the analytes was achieved using positive ion electrospray tandem mass spectrometry in selected reaction monitoring (SRM) mode. The linear standard curve ranged from 100 to 5000 ng/mL and the precision and accuracy (inter- and intra-run) were within 7.9% and 4.9%, respectively. The method was successfully used to determine clarithromycin concentrations in human plasma samples obtained from healthy subjects who were given clarithromycin 500 mg for 3 days. The method is rapid, simple, precise and directly applicable to clarithromycin pharmacokinetic studies.

Background Coenzyme Q10 (CoQ10) is a provitamin synthesized via the 3-hydroxy-3-methyl-glutaryl coenzyme A (HMG-CoA) reductase pathway, and thus may serve as a potential marker of intrinsic HMG-CoA reductase activity. HMG-CoA reductase inhibitors (statins) decrease CoQ10, although it is unclear whether this is due to reductions in lipoproteins, which transport CoQ10. Objective We evaluated whether baseline plasma CoQ10 concentrations predict lipid-lowering response to high-dose atorvastatin, and to what extent CoQ10 changes after atorvastatin therapy depend on lipoprotein changes. Methods Individuals without dyslipidemia or known cardiovascular disease (n = 84) received atorvastatin 80 mg/day for 16 weeks. Blood samples collected at baseline and after 4, 8, and 16 weeks of treatment were assayed for CoQ10. Results Individuals with higher baseline CoQ10/low-density lipoprotein cholesterol (LDL-C) ratios displayed diminished absolute and percent LDL-C reductions at 8 and 16 weeks of atorvastatin treatment ( P P = 0.01). After 16 weeks of atorvastatin, plasma CoQ10 decreased 45% from 762 ± 301 to 374 ± 150 ng/mL ( P r = 0.27 − 0.38; P = 0.001 to P = 0.02), but remained significant when normalized to all lipoproteins. CoQ10 changes were not associated with adverse drug reactions. Conclusion Baseline CoQ10/LDL-C ratio was associated with the degree of LDL-C response to atorvastatin. Atorvastatin decreased CoQ10 concentrations in a manner that was not completely dependent on lipoprotein changes. The utility of CoQ10 as a predictor of atorvastatin response should be further explored in patients with dyslipidemia.

A sensitive and specific HPLC–MS/MS method was developed for the analysis of mycophenolic acid glucuronide (MPAG) in incubations with human liver microsomes. Incubation samples were processed by protein precipitation with acetonitrile. MPAG and the internal standard phenolphthalein glucuronide were chromatographed on a C18 Synergi Fusion-RP column (100 mm × 2 mm, 4 μm) using gradient elution with a mixture of 1 mM acetic acid in deionized water and 1 mM acetic acid in acetonitrile at a flow rate of 0.22 mL/min. The mass spectrometer was operated with negative electrospray ionization and analysis was carried out in the single reaction monitoring (SRM) mode using the mass transitions of m / z 495 → 319 and m / z 493 → 175 for MPAG and phenolphthalein glucuronide, respectively. The MPAG calibration curve was linear over the concentration range of 1.0–20 μM. The within-day and between-day relative standard deviations ranged from 1.1 to 7.9% and accuracy was within 8%. The simple and reproducible method is suitable for measuring mycophenolic acid glucuronidation in microsomal incubations.

Hydrochlorothiazide is among the most commonly prescribed antihypertensives; yet, PRKAG2 , rs12604940 DCC , and rs13262930 EPHX2 ) along with arachidonic acid, converging in the netrin signaling pathway ( P =1×10 −5 ), as potential markers, significantly influencing hydrochlorothiazide BP response. We successfully replicated the 3 genetic signals in 212 white hypertensives treated with hydrochlorothiazide and created a response score by summing their BP-lowering alleles. We found patients carrying 1 response allele had a significantly lower response than carriers of 6 alleles (∆SBP/∆DBP: −1.5/1.2 versus −16.3/−10.4 mm Hg, respectively, SBP score, P =1×10 −8 and DBP score, P =3×10 −9 ). This score explained 11.3% and 11.9% of the variability in hydrochlorothiazide SBP and DBP responses, respectively, and was further validated in another independent study of 196 whites treated with hydrochlorothiazide (DBP score, P =0.03; SBP score, P =0.07). This study suggests that PRKAG2 , DCC , and EPHX2 might be important determinants of hydrochlorothiazide BP response.

Aims We investigated flurbiprofen pharmacokinetics in 12 volunteers to develop a phenotypic trait measure that correlates with the fractional clearance to 4′-hydroxyflurbiprofen. The effect of the CYP2C9 inhibitor fluconazole on flurbiprofen metabolism was also evaluated. Methods Flurbiprofen pharmacokinetics were evaluated before and after the first and seventh doses of fluconazole. The urinary recovery ratio was calculated as FLRR = 4′-OHF/[4′-OHF + Ftot] and the urinary metabolic ratio was calculated as FLMR = 4′-OHF/Ftot, where 4′-OHF and Ftot represent total (conjugated and unconjugated) amounts recovered in urine. Results There was a statistically significant relationship between the 4′-OHF formation clearance (4OHCLf) and both the 8-h FLRR and the 8-h FLMR with and without administration of fluconazole. The flurbiprofen apparent oral clearance (CL/F) was decreased by 53% [90% confidence interval (CI) −58, −48] and 64% (90% CI −69, −59), respectively, after administration of one and seven doses of fluconazole when compared with administration of flurbiprofen alone; similarly, the 4OHCLf decreased by 69% (90% CI −74, −64) and 78% (90% CI −83, −73), the 8-h FLRR decreased by 35% (90% CI −41, −29) and 40% (90% CI −46, −35) and the 8-h FLMR decreased by 61% (90% CI −65, −58) and 67% (90% CI −70, −63). The magnitude of decrease in CL/F and 4OHCLf was greater after seven doses compared with after one dose of fluconazole (P

Background Little information is available on the disposition of vancomycin during chronic peritoneal dialysis (PD) in children. The primary objective of this study was to investigate the disposition of vancomycin following intraperitoneal (IP) administration in children receiving short-dwell [ e.g., automated PD (APD)] and long-dwell [ e.g., continuous ambulatory PD (CAPD)] PD. Methods A 6-hour exchange containing vancomycin 500 mg/L, using an exchange volume of 1100 mL/m2 body surface area (BSA), was followed by 4-, 6-, and 8-hour antibiotic-free exchanges. The 8-hour exchange was followed by three to four 90-minute antibiotic-free exchanges. Serial blood and dialysis effluent samples were obtained and analyzed for vancomycin concentration by high-pressure liquid chromatography. Pharmacokinetic parameters were computed using noncompartmental methods. Results The bioavailability of vancomycin during a 6-hour IP exchange was 70% ± 5%, resulting in a delivered dose of 12.0 ± 1.8 mg/kg, and a 6-hour serum vancomycin concentration of 23.3 ± 7.2 μg/mL. Total body vancomycin clearance measured 10.72 ± 4.52 mL/minute/1.73 m2 BSA, while clearance attributable to PD measured 2.78 ± 1.08 mL/min/1.73 m2 BSA and accounted for 29% ± 11% of total vancomycin clearance. Dialysis clearance during long-dwell (CAPD) and short-dwell (APD) regimens was similar, measuring 2.46 ± 1.04 and 3.09 ± 1.28 mL/min/1.73 m2 BSA, accounting for 25% ± 13% and 32% ± 12% of total body clearance respectively. Conclusions Intraperitoneal absorption and dialysis clearance of vancomycin in children receiving PD are similar to those reported in adult dialysis patients. In contrast, total body clearance of vancomycin appears to be increased and the elimination half-life decreased in children, due to increased elimination by non-renal nondialysis routes. For intermittent IP vancomycin therapy in children with peritonitis, an IP load containing vancomycin 1000 mg/L (or 30 mg/kg), followed a single full-fill (1100 mL/m2 BSA) daily exchange, containing vancomycin 250 mg/L (or 7.5 mg/kg), from day 2 until the end of treatment will maintain a vancomycin dialysate concentration of >4 μg/mL.

Introduction: β-blockers, including atenolol, are among the most widely prescribed antihypertensive drug classes. However, their use has been associated with hyperglycemia and incident diabetes, which poses concern for prescribers and patients. The Pharmacogenomic Evaluation of Antihypertensive Responses (PEAR) study is a multicenter clinical trial with one of its objectives to identify genetic influences on adverse metabolic events in patients treated with atenolol. Here we report a genomics-metabolomics integrative approach to identify biomarkers associated with atenolol-induced glucose change. Methods: PEAR participants were genotyped using the Illumina Omni 1M-Quad Chip. Metabolite profiles were acquired through GC-TOF-MS. Association between baseline levels of metabolites and glucose change was conducted using a multivariate linear regression model adjusted for age, gender and baseline fasting glucose. Genomics-metabolomics integration included selecting SNPs within genes involved in the synthesis and degradation of top metabolites and testing their effect on glucose change in 234 atenolol-treated Caucasians in PEAR, adjusting for age, gender, baseline glucose and principal components 1 and 2. A false discovery rate (FDR) of .05 was used to adjust for multiple comparisons. Replication of significant SNPs was conducted in an additional 228 participants treated with atenolol in PEAR. Results: Metabolomics analysis revealed 3 metabolites associated with glucose change that passed FDR adjustment. The top metabolite signal was beta-alanine. Increasing levels of baseline beta-alanine was significantly correlated with greater glucose increases after atenolol treatment (p=.0003). A total of 79 SNPs in 12 genes in the beta-alanine pathway were explored. SNP rs2669429 in DPYS was significantly associated with glucose change, after FDR adjustment. We found that G allele carriers had significantly greater glucose change compared with non-carriers (p=.0006; β=+2.76 mg/dL). This finding was successfully replicated in the other 228 patients who received atenolol (p=.04; β=+1.86 mg/dL). Conclusions: These results suggest that beta alanine and DPYS rs2669429 SNP might be an important predictor of atenolol-induced dysglycemia.

Achieving hypertension (HTN) control and mitigating the adverse health effects associated with HTN continues to be a global challenge. Some individuals respond poorly to current HTN therapies, and mechanisms for response variation remain poorly understood. We used a nontargeted metabolomics approach (gas chromatography time-of-flight/mass spectrometry gas chromatography time-of-flight/mass spectrometry) measuring 489 metabolites to characterize metabolite signatures associated with treatment response to anti-HTN drugs, atenolol (ATEN), and hydrochlorothiazide (HCTZ), in white and black participants with uncomplicated HTN enrolled in the Pharmacogenomic Evaluation of Antihypertensive Responses study. Metabolite profiles were significantly different between races, and metabolite responses associated with home diastolic blood pressure (HDBP) response were identified. Metabolite pathway analyses identified gluconeogenesis, plasmalogen synthesis, and tryptophan metabolism increases in white participants treated with HCTZ (P

The effects of conjugated equine estrogens (CEE) 0.625 mg daily on cytochrome P450 (CYP) were quantified in 12 middle-aged and 13 elderly postmenopausal women at baseline and 6 months later. CYP phenotype was characterized by caffeine (CYP1A2), chlorzoxazone (CYP2E1), dapsone (CYP, N-acetyltransferase 2), dextromethorphan (CYP2D6), and mephenytoin (CYP2C19) metabolism. CEE significantly decreased CYP1A2 (caffeine metabolic ratio: 0.57 +/- 0.20 before, 0.40 +/- 0.20 after, P = .001) and significantly increased CYP2D6 (dextromethorphan/dextrorphan ratio: 0.0116 +/- 0.0143 before, 0.0084 +/- 0.0135 after, P = .022) metabolism. CEE had no overall effect on CYP2C19, CYP2E1, CYP-mediated dapsone metabolism, and N-acetyltransferase 2. The dextromethorphan metabolic ratio decreased only in the seniors. The dapsone recovery ratio decreased in the middle-aged group and increased in the seniors. CEE significantly influenced CYP1A2, CYP2D6, and CYP-mediated dapsone oxidative metabolism but not CYP2C19, CYP2E1, or N-acetyltransferase 2 metabolism in postmenopausal women. Age influenced CYP2D6 metabolism and dapsone hydroxylation.

Background We have previously shown that flurbiprofen metabolism to 4′-hydroxyflurbiprofen provides an in vivo measure of cytochrome P450 (CYP) 2C9 activity. This study evaluated the possibility of incorporating flurbiprofen into the current 5-drug Pittsburgh cocktail. Methods In a randomized, 3-way, Latin-square, crossover-design study, 24 healthy subjects (mean age [±SD], 47.8 ± 15.1 years) received flurbiprofen (50 mg) and the Pittsburgh 5-drug cocktail (100 mg caffeine, 100 mg mephenytoin, 10 mg debrisoquin [INN, debrisoquine], 250 mg chlorzoxazone, and 100 mg dapsone) separately and in combination on 3 occasions over a period of 5 weeks. Urine was collected from 0 to 8 hours, and plasma was obtained at 4 and 8 hours after drug administration. Parent drug and metabolite concentrations were measured to determine phenotypic indices for each of the metabolizing enzymes. Results The geometric mean ratio and 90% confidence interval of the phenotypic indices were included within the 80% to 125% bioequivalence range for each of the probe drugs. There were no statistically significant differences between the phenotypic indices determined after administration of the 5-drug and 6-drug cocktails. However, there was a small but statistically significant increase (7.5%, P = .03) in the 8-hour urinary flurbiprofen recovery ratio after administration of the 6-drug cocktail compared with that after administration of flurbiprofen alone. The 6-drug cocktail was well tolerated. Conclusion The results of this study show that caffeine (CYP1A2), chlorzoxazone (CYP2E1), dapsone (N-acetyltransferase 2), debrisoquin (CYP2D6), flurbiprofen (CYP2C9), and mephenytoin (CYP2C19) can be simultaneously administered in low doses without metabolic interaction. Clinical Pharmacology & Therapeutics (2006) 80, 257–263; doi: 10.1016/j.clpt.2006.06.005

Previous reports have supported the concept that messenger ribonucleic acid (mRNA) concentrations for cytochrome P450 (CYP) enzymes in peripheral blood mononuclear cells may be predictive of systemic enzyme activity. We investigated whether changes in mRNA expression for CYP1A2,CYP2C19, CYP2D6 and CYP3A4 in peripheral blood lymphocytes (PBLs) may serve as surrogate markers for changes in CYP enzyme activity following the administration of rifampin.On day 1 and day 9 of the study, 12 healthy volunteers were administered caffeine 100 mg, debrisoquine 10 mg and omeprazole 40 mg orally, along with midazolam 0.025 mg/kg intravenously. Blood samples and urine were collected for 8 h after drug administration. The subjects took rifampin 300 mg (n = 6) or 600 mg (n = 6) daily on days 2-8. Total RNA was isolated from PBLs on day 1 and day 9, and mRNA expression for the CYP enzymes and hGAPDH were determined by means of quantitative, real-time, reverse-transcriptase polymerase chain reaction. CYP1A2 activity was estimated by calculating the plasma paraxanthine to caffeine AUC ratio (caffeine metabolic ratio; CMR), CYP2C19 activity by the 2-h omeprazole hydroxylation index (HI), CYP2D6 activity by the urinary debrisoquine recovery ratio (DBRR) and CYP3A4 activity by midazolam clearance.Median midazolam clearance (0.362 to 0.740 l/kg/h), omeprazole HI (0.752 to 0.214), CMR (0.365 to 0.450) and DBRR (0.406 to 0.479) all changed significantly following rifampin, consistent with the expected enzyme induction. CYP1A2,CYP2D6 and CYP3A4 mRNA content were measurable in all samples. CYP2C19 mRNA was inconsistently detectable. There were no significant correlations between changes in enzyme activity and mRNA expression by Spearman's rank order correlation.The results do not support the use of mRNA expression assays for CYP1A2, CYP2C19, CYP2D6 and CYP3A4 enzymes in PBLs as surrogates for quantifying changes in systemic enzyme activity in the setting of enzyme induction.

ObjectiveThis study determined the pharmacokinetics of intraperitoneal (IP) cefepime in automated peritoneal dialysis (APD) patients.Design and MethodsA prospective pharmacokinetic study was performed in 6 noninfected adult APD patients. All patients were administered a single IP dose of cefepime (15 mg/kg) over a 6-hour dwell. Patients then underwent a fixed APD regimen consisting of the first 6-hour dwell, followed by an 8-hour dialysate-free period and a subsequent series of 3 overnight APD exchanges. Blood and dialysate samples were collected at t = 0, 1, 2, 4, 6 (end of dwell), and 24 hours. Any urine produced during the study period was collected. Cefepime concentrations in serum, dialysate, and urine were determined by liquid chromatography mass spectrometry. Pharmacokinetic parameters were calculated assuming a mono-exponential model.ResultsOne hour after IP administration, serum cefepime levels exceeded the minimum inhibitory concentration (8 μg/mL) for susceptible organisms. The mean serum and dialysate concentrations at 24 hours were 15.8 ± 3.6 and 6.2 ± 2.3 μg/mL respectively. Bioavailability was 84.3% ± 6.2%, volume of distribution 0.34 ± 0.07 L/kg, and serum half-life 13.8 ± 3.2 hours. Total, peritoneal, and renal clearances were 16.5 ± 4.4, 4.3 ± 0.7, and 3.5 ± 2.5 mL/minute, respectively.ConclusionsIP cefepime dosed at 15 mg/kg resulted in adequate serum concentrations in APD patients at 24 hours post dose. Pharmacokinetic predictions suggest that most APD and CAPD patients would achieve adequate serum cefepime concentrations if treated with standard doses of 1000 mg given IP once daily. Patients using APD regimens different from that used in this study, anuric patients, and those with significant residual renal function may require a more individualized approach.