Exposure-response modelling for empagliflozin, a sodium glucose cotransporter 2 (SGLT2) inhibitor, in patients with type 2 diabetes.

AIMS: To provide model-based clinical development decision support including dose selection guidance for empagliflozin, an orally administered sodium glucose cotransporter 2 inhibitor, through developed exposure-response (E-R) models for efficacy and tolerability in patients with type 2 diabetes mellitus (T2DM). METHODS: Five randomized, placebo-controlled, multiple oral dose studies of empagliflozin in patients with T2DM (n = 974; 1-100 mg once daily, duration ≤12 weeks) were used to develop E-R models for efficacy (glycosylated haemoglobin [HbA1c ], fasting plasma glucose [FPG] and urinary glucose excretion). Two studies (n = 748, 12 weeks) were used to evaluate tolerability E-R. RESULTS: The efficacy model predicted maximal decreases in FPG and HbA1c of 16% and 0.6%, respectively, assuming a baseline FPG concentration of 8 mm (144 mg dl(-1) ) and 10-25 mg every day empagliflozin targeted 80-90% of these maximums. Increases in exposure had no effect on incidence rates of hypoglycaemia (n = 4), urinary tract infection (n = 17) or genital/vulvovaginal-related (n = 16) events, although low prevalence rates may have precluded more accurate evaluation. CONCLUSIONS: E-R analyses indicated that 10 and 25 mg once daily empagliflozin doses achieved near maximal glucose lowering efficacy.

Steady-state pharmacokinetics of nevirapine extended-release tablets in HIV-1-infected children and adolescents: an open-label, multiple-dose, cross-over study.

BACKGROUND: To compare steady-state (ss) pharmacokinetic targets of nevirapine extended-release (NVP-XR) tablets once-daily (QD) with immediate-release (NVP-IR) tablet or oral suspension twice-daily in HIV-1-infected children and adolescents. METHODS: Phase I, open-label, multidose, cross-over study with optional extension phase, in 85 patients 3 to <18 years of age, previously on an NVP-IR-based regimen for ≥18 weeks with baseline viral load <50 copies/mL. Patients were stratified by age, treated with NVP-IR twice-daily for 11 days, then NVP-XR QD for 10 days. Cpre,ss (steady-state, predose concentrations) was obtained from all, and 12-hour NVP-IR and 24-hour NVP-XR steady-state pharmacokinetic profiles were obtained in the pharmacokinetic substudy. Viral loads, CD4 counts and adverse events (AEs) were monitored. RESULTS: Eighty patients completed the trial. Adjusted geometric mean (gMean) Cpre,ss for NVP-XR and NVP-IR exceeded the target of 3000 ng/mL, and the adjusted gMean NVP-XR:NVP-IR ratio (90% confidence interval) for QD normalized and un-normalized Cpre,ss were 91.2% (83.5-99.6%) and 91.8% (83.7-100.7%). gMean 24-hour area under the curve at steady-state NVP-XR:NVP-IR for un-normalized dose was 90.4% and un-normalized Cpre,ss NVP-XR:NVP-IR were 91.0%, 81.9% and 103.7% for the 3 age groups, 3 to <6, 6 to <12 and 12 to <18 years, respectively. gMean values indicated no exposure to subtherapeutic NVP concentrations and viral suppression was adequate and maintained in all QD groups. Most AEs were mild and similar between age groups. No serious or Division of AIDS Grade 4 AEs or AE related treatment discontinuations occurred. CONCLUSIONS: NVP-XR exhibited adequate trough concentrations with equivalent area under the curve at steady-state relative to NVP-IR. NVP-XR was well-tolerated and is a valuable treatment option for HIV-infected children and adolescents.

Population pharmacokinetics of empagliflozin, a sodium glucose cotransporter 2 inhibitor, in patients with type 2 diabetes.

Data from five randomized, placebo-controlled, multiple oral dose studies of empagliflozin in patients with type 2 diabetes mellitus (T2DM; N = 974; 1-100 mg q.d.; ≤12 weeks) were used to develop a population pharmacokinetic (PK) model for empagliflozin. The model consisted of two-compartmental disposition, lagged first-order absorption and first-order elimination, and incorporated appropriate covariates. Population estimates (interindividual variance, CV%) of oral apparent clearance, central and peripheral volumes of distribution, and inter-compartmental clearance were 9.87 L/h (26.9%), 3.02 L, 60.4 L (30.8%), and 5.16 L/h, respectively. An imposed allometric weight effect was the most influential PK covariate effect, with a maximum effect on exposure of ±30%, using 2.5th and 97.5th percentiles of observed weights, relative to the median observed weight. Sex and race did not lend additional description to PK variability beyond allometric weight effects, other than ∼25% greater oral absorption rate constant for Asian patients. Age, total protein, and smoking/alcohol history did not affect PK parameters. Predictive check plots were consistent with observed data, implying an adequate description of empagliflozin PKs following multiple dosing in patients with T2DM. The lack of marked covariate effects, including weight, suggests that no exposure-based dose adjustments were required within the study population and dose range.

Integration of absorption, distribution, metabolism, and elimination genotyping data into a population pharmacokinetic analysis of nevirapine.

OBJECTIVES: The aim of this analysis was to show the applicability of a newly developed algorithm to assess the influence of genetic variants and other covariates on nevirapine's drug disposition. The algorithm combines high-throughput genotyping data and nonlinear mixed effects modeling methods. METHODS: Patients, who participated in the 2NN pharmacokinetic sub study, were reconsented and reenrolled into a clinical trial for genotyping analysis. Overall, 198 single nucleotide polymorphisms located in 45 absorption, distribution, metabolism, and elimination related genes were genotyped using the Illumina BeadArray technology. Data analysis was performed using NONMEM VI and SAS 9.1.3. RESULTS: Overall, 1260 nevirapine plasma concentrations were obtained from 271 genotyped patients. Plasma concentration-time profiles of nevirapine were best described by a one-compartment model with auto-induced first-order elimination process. Nevirapine clearance was 19.4% reduced in Asian/Black patients, compared with Caucasian/Hispanic patients. For single nucleotide polymorphism rs3745274 (CYP2B6 516G>T) heterozygous patients (GT) showed a 15.3% reduced clearance; patients with homozygous CYP2B6 516TT alleles showed a 30.6% reduced clearance compared to patients with homozygous 516GG alleles. Patients carrying the homozygote genotype of rs12768009 (CYP2C19 8403AA), highly linked to rs4244285 (CYP2C19*2), showed a 26.8% reduced clearance compared with patients with CYP2C19 8403 AG and GG alleles. CONCLUSION: By integration of high-throughput genotyping data into a pharmacometric analysis of nevirapine, the impact of the CYP2B6 516G>T polymorphism on nevirapine's exposure was confirmed and quantified. In addition, a new hypothesis with regard to CYP2C19 involvement in nevirapine metabolism has been generated. The analysis presented might help to optimize and individualize the therapy for patients treated with nevirapine to add to their therapeutic benefit.

Lack of a pharmacokinetic interaction between steady-state tipranavir/ritonavir and single-dose valacyclovir in healthy volunteers.

OBJECTIVE: This study assessed the single-dose pharmacokinetics of the herpes antiviral acyclovir (administered as the pro-drug valacyclovir) alone and in combination with twice-daily 200 mg ritonavir-boosted tipranavir (500 mg) at steady state. METHODS: The study was an open label, one-sequence cross-over pharmacokinetic study in HIV-negative adults. Plasma drug concentrations were measured by validated LC/MS/MS assays; pharmacokinetics (AUC, C(max)) were determined using noncompartmental methods. The geometric mean ratio and 90% confidence interval [GMR, 90% CI] were used to evaluate the drug interaction. RESULTS: Twenty-six of 29 subjects completed the trial. With steady-state tipranavir/ritonavir, acyclovir C(max) decreased 4.9% [0.95, 0.88-1.02] and AUC increased 6.6% [1.07, 1.04-1.09]. The majority of subjects experienced at least one adverse event, most of which were mild gastrointestinal disorders. Three subjects discontinued tipranavir/ritonavir treatment as a result of drug-related increases in ALT/AST, including one subject who experienced mild upper abdominal pain. All subjects recovered without sequelae. CONCLUSIONS: When administered as a single dose of valacyclovir with steady-state tipranavir/ritonavir, there were no clinically important changes in acyclovir pharmacokinetics. This result indicates that valacyclovir can be co-administered safely with no dose adjustments.

Concomitant administration of BILR 355/r with emtricitabine/tenofovir disoproxil fumarate increases exposure to emtricitabine and tenofovir: a randomized, open-label, prospective study.

The objective of this study was to evaluate the pharmacokinetic interaction of ritonavir-boosted BILR 355 (BILR 355/r) with emtricitabine (FTC)/tenofovir disoproxil fumarate (TDF). This was an open-label, prospective study. For Group A, 26 healthy subjects were given FTC/TDF (200/300 mg) once daily (QD) for 7 days and then co-administered with BILR 355/r (150/100 mg) twice daily (bid) for an additional 7 days. Pharmacokinetics assessments were performed at days 7 and 14. For Group B, eight subjects were given BILR 355/r (150/100 mg) bid for 7 days. The pharmacokinetic data from Group B were also pooled with Group B subjects from other similar studies performed in parallel to this study. After co-administration with BILR 355/r, the geometric mean ratio (GMR, %) and 90% confidence interval (CI, %) of combined versus alone treatment for FTC AUC(0-24,ss) , C(max,ss) and C(0-12,ss) were 160 (154-166), 128 (121-136) and 223 (206-241), respectively; and for tenofovir AUC(0-24,ss) , C(max,ss) and C(24,ss) were 126 (121-132), 131 (117-146) and 132 (124-140), respectively. Co-administration with FTC/TDF resulted in an 18% increase in AUC(0-12,ss) , 14% increase in C(max,ss) and 19% increase in C(12,ss) for BILR 355. BILR 355 was well tolerated in this study. There was no evidence of increased risk of TFV or FTC toxicity upon co-administration of FTC/TDF with BILR 355/r.

Coadministration with lopinavir and ritonavir decreases exposure to BILR 355, a nonnucleoside reverse transcriptase inhibitor, in healthy volunteers.

The objective of this investigation was to evaluate the pharmacokinetic interaction of lopinavir/ritonavir (LPV/r) with BILR 355. In group A, 26 healthy participants were administered LPV/r (400mg/100mg) twice daily for 14 days, followed by coadministration of BILR 355, 150 mg twice daily for an additional 7 days. Pharmacokinetic assessments were performed on days 14 and 21. In group B, 8 healthy participants were given BILR 355/ritonavir (BILR 355/r, 150 mg/100mg) twice daily for 7 days. The pharmacokinetic data from group B (BILR 355/r-alone group) were also pooled with group B subjects from 3 similar phase I drug-drug interaction trials performed in parallel to this study. Coadministration with LPV/r resulted in a 51% decrease in steady-state area under plasma concentration-time curve from 0 to 12 hours (AUC(0-12,ss)) and steady-state maximum measured plasma concentration over a dosing interval (C(max,ss)) and a 50% decrease in steady-state plasma concentration 12 hours post last dosing (C(12,ss)) for BILR 355. Exposure to LPV was not changed after coadministration. BILR 355/r was well tolerated in this study. There was no evidence of increased risk of lopinavir or ritonavir toxicity upon coadministration with BILR 355.

Pharmacokinetic characterization of three doses of tipranavir boosted with ritonavir on highly active antiretroviral therapy in treatment-experienced HIV-1 patients.

PURPOSE: This study characterized the pharmacokinetic effects, safety, and antiretroviral activity of three different doses of the nonpeptidic protease inhibitor tipranavir, in combination with ritonavir administered twice daily for 28 days, on a number of triple-combination regimens containing a nonnucleoside reverse transcriptase inhibitor (efavirenz or nevirapine) plus two nucleoside reverse transcriptase inhibitors (abacavir, didanosine, lamivudine, stavudine, and zidovudine) or a three nucleoside reverse transcriptase inhibitor combination (zidovudine, lamivudine, and abacavir). METHODS: The study enrolled 208 HIV-1-positive patients who had been on stable antiretroviral treatment for at least 12 weeks prior to study entry and had an HIV-1 RNA load of delta 20,000 copies/mL. The patients were randomized to receive one of three dose combinations of tipranavir and ritonavir (1250/100 mg, 750/100 mg, and 250/200 mg) in addition to their antiretroviral (ARV) regimen for the next 22 days. The effects of twice-daily tipranavir and ritonavir combinations on the steady-state pharmacokinetics of the antiretrovirals were assessed by comparing pharmacokinetic parameters at baseline and after 3 weeks of coadministration. RESULTS: No clinically relevant changes were observed in the Cmin, Cmax, or AUC parameters for nevirapine, efavirenz, lamivudine, stavudine, or didanosine, when coadministered with tipranavir and ritonavir at the dose combinations studied. All three dose combinations of tipranavir and ritonavir decreased the systemic exposure of abacavir (by 35% to 44%) and zidovudine (by 31% to 42%). Consistent with previous tipranavir studies, gastrointestinal adverse events were those most frequently observed. These reactions tended to be mild, with the majority being of Grade 1, and only 8 being of Grade 3 or 4 in intensity. Virologic response improved from 40.4% of participants at baseline with <50 copies/mL to 67.6% at Day 28 of study following addition of tipranavir and ritonavir. CONCLUSIONS: Tipranavir coadministered with ritonavir has been demonstrated to be safe, effective, and pose little potential for clinically meaningful drug interactions when added to the highly active antiretroviral therapy regimens containing nevirapine, efavirenz, lamivudine, stavudine, or didanosine.

In vitro-in vivo correlation for nevirapine extended release tablets.

An in vitro-in vivo correlation (IVIVC) for four nevirapine extended release tablets with varying polymer contents was developed. The pharmacokinetics of extended release formulations were assessed in a parallel group study with healthy volunteers and compared with corresponding in vitro dissolution data obtained using a USP apparatus type 1. In vitro samples were analysed using HPLC with UV detection and in vivo samples were analysed using a HPLC-MS/MS assay; the IVIVC analyses comparing the two results were performed using WinNonlin. A Double Weibull model optimally fits the in vitro data. A unit impulse response (UIR) was assessed using the fastest ER formulation as a reference. The deconvolution of the in vivo concentration time data was performed using the UIR to estimate an in vivo drug release profile. A linear model with a time-scaling factor clarified the relationship between in vitro and in vivo data. The predictability of the final model was consistent based on internal validation. Average percent prediction errors for pharmacokinetic parameters were <10% and individual values for all formulations were <15%. Therefore, a Level A IVIVC was developed and validated for nevirapine extended release formulations providing robust predictions of in vivo profiles based on in vitro dissolution profiles.

Assessment of nevirapine bioavailability from targeted sites in the human gastrointestinal tract.

This study investigated absorption of nevirapine (NVP) from targeted sites of the gastrointestinal tract using remotely activated capsules and gamma scintigraphy. A total of 24 participants were randomized to receive 50 mg NVP orally as a suspension or via remotely activated capsules for release into the ascending colon. The 24 participants were then rerandomized into parallel groups of n = 8 for drug release into the ileum, jejunum, or descending colon. The mean gastric emptying time of capsules ranged from 0.88 to 3.35 hours. The small intestinal and colon transit time ranged from 4.08 to 7.76 hours and 17.6 to 21.2 hours, respectively, and capsule recovery time ranged from 27.6 to 34.4 hours. The relative bioavailability ratio of NVP in the jejunum was 1.06 (90% confidence interval [CI]: 1.00-1.12) compared to suspension. In the ileum, ascending colon, and descending colon, bioavailability decreased to 0.89 (0.80-0.99), 0.82 (0.71-0.95), and 0.58 (0.22-1.53), respectively. The absorption rate decreased by approximately 10-fold from the jejunum (3.83 h(-1)) to the descending colon (0.338 h(-1)), and t(max) increased from 2.42 hours (jejunum) to 16.3 hours (descending colon). Overall, NVP is absorbed from all 4 sites of the gastrointestinal tract, and the rate of absorption decreased from the jejunum to the descending colon. Relative bioavailability of NVP was in the order of jejunum > ileum > ascending colon > descending colon.

Pharmacokinetic assessment of nevirapine and metabolites in human immunodeficiency virus type 1-infected patients with hepatic fibrosis.

Nevirapine is a nonnucleoside reverse transcriptase inhibitor used as part of combination therapy for human immunodeficiency virus (HIV) infection. Nevirapine may be prescribed for patients with hepatic fibrosis and cirrhosis. Significant autoinduction of cytochrome P450 3A4 and 2B6 following multiple dosing prompted an assessment of the metabolic profiles in patients with liver disease receiving chronic nevirapine therapy. HIV-infected patients with hepatic fibrosis who were receiving a stable antiretroviral regimen containing nevirapine for > or = 6 weeks had liver biopsy specimens assessed by Ishak histologic scoring and were grouped by severity (group 1, Ishak scores of 1 and 2; group 2, Ishak scores of 3 and 4; group 3, Ishak scores of 5 and 6). Steady-state trough nevirapine levels were determined for all patients, and additional measurements were obtained at 1, 2, and 4 h following nevirapine dosing for a subset of patients. The pharmacokinetics of nevirapine and its five metabolites were characterized, and a comparison of the results for the different Ishak groups was performed. Among 51 patients with hepatic fibrosis, the majority of whom were coinfected with hepatitis C virus or hepatitis B virus, differences between the maximum and the minimum observed plasma concentrations demonstrated a statistically significant flattening of the systemic exposure curves with progression from Ishak group 1 to Ishak group 2 or 3, suggesting a decrease in systemic clearance with the progression of liver disease. However, there were no significant differences in the trough and the maximum nevirapine concentrations between the Ishak groups. The metabolite profiles were also comparable across the Ishak groups. In HIV-infected patients who were chronically treated with nevirapine and who had various degrees of hepatic fibrosis, including cirrhosis, trough plasma nevirapine concentrations were not significantly increased, and thus, no dose adjustment is warranted.

Pharmacokinetics of BILR 355 after multiple oral doses coadministered with a low dose of ritonavir.

The pharmacokinetics and safety of BILR 355 following oral repeated dosing coadministered with low doses of ritonavir (RTV) were investigated in 12 cohorts of healthy male volunteers with a ratio of 6 to 2 for BILR 355 versus the placebo. BILR 355 was given once a day (QD) coadministered with 100 mg RTV (BILR 355/r) at 5 to 50 mg in a polyethylene glycol solution or at 50 to 250 mg as tablets. BILR 355 tablets were also dosed at 150 mg twice a day (BID) coadministered with 100 mg RTV QD or BID. Following oral dosing, BILR 355 was rapidly absorbed, with the mean time to maximum concentration of drug in serum reached within 1.3 to 5 h and a mean half-life of 16 to 20 h. BILR 355 exhibited an approximately linear pharmacokinetics for doses of 5 to 50 mg when given as a solution; in contrast, when given as tablets, BILR 355 displayed a dose-proportional pharmacokinetics, with a dose range of 50 to 100 mg; from 100 to 150 mg, a slightly downward nonlinear pharmacokinetics occurred. The exposure to BILR 355 was maximized at 150 mg and higher due to a saturated dissolution/absorption process. After oral dosing of BILR 355/r, 150/100 mg BID, the values for the maximum concentration of drug in plasma at steady state, the area under the concentration-time curve from 0 to the dose interval at steady state, and the minimum concentration of drug in serum at steady state were 1,500 ng/ml, 12,500 h.ng/ml, and 570 ng/ml, respectively, providing sufficient suppressive concentration toward human immunodeficiency virus type 1. Based on pharmacokinetic modeling along with the in vitro virologic data, several BILR 355 doses were selected for phase II trials using Monte Carlo simulations. Throughout the study, BILR 355 was safe and well tolerated.

Pharmacokinetic and safety evaluation of BILR 355, a second-generation nonnucleoside reverse transcriptase inhibitor, in healthy volunteers.

BILR 355 is a second-generation nonnucleoside reverse transcriptase inhibitor (NNRTI) under clinical development for the treatment of human immunodeficiency virus infection, particularly in those who harbor virus resistant to the currently available NNRTIs. Two single-center, double-blinded, placebo-controlled, parallel dose-escalation studies were conducted to evaluate the pharmacokinetics and safety of oral BILR 355 administration alone and after coadministration with ritonavir (RTV) at 100 mg. Following a single dose of BILR 355 in oral solution, the mean half life (t(1/2)) was 2 to 4 h, with peak concentrations occurring at 0.5 to 1 h postadministration. The mean apparent clearance (CL/F) ranged from 79.2 to 246 liters/h for administered doses of 12.5 mg to 100 mg. This observed nonlinearity in CL/F resulted from the increased bioavailability attributed to a saturated absorption and/or elimination process at higher doses. In contrast, after the coadministration of single doses of 5 mg to 87.5 mg of BILR 355 with RTV, the mean CL/F ranged from 5.88 to 8.47 liters/h. Over the dose range (5 to 87.5 mg) studied, systemic BILR 355 exposures were approximately proportional to the doses administered when they were coadministered with RTV. With RTV coadministration, the mean t(1/2) increased to 10 to 16 h, and the mean time of the maximum concentration in plasma lengthened to 1.5 to 5 h. Compared to the values for BILR 355 given alone, the mean area under the concentration-time curve from time zero to infinity, the maximum concentration in plasma, and the t(1/2) of BILR 355 achieved after coadministration with RTV increased 15- to 30-fold, 2- to 5-fold, and 3- to 5-fold, respectively. In both studies, BILR 355 appeared to be safe and well tolerated in healthy volunteers when the outcomes in the treated volunteers were compared with those in the placebo group.

Pharmacokinetics, safety, and efficacy of tipranavir boosted with ritonavir alone or in combination with other boosted protease inhibitors as part of optimized combination antiretroviral therapy in highly treatment-experienced patients (BI Study 1182.51).

BACKGROUND: Given the limited treatment options for patients with high-level resistance, antiretroviral (ARV) regimens based on concomitant use of 2 ritonavir (RTV)-boosted protease inhibitors (PIs) were considered a therapeutic option. METHODS: Boehringer Ingelheim (BI) study 1182.51 examined the pharmacokinetic profile, safety, and efficacy of RTV-boosted tipranavir (TPV/r), alone and in combination with comparator PIs (CPIs) in 315 triple-class-experienced, HIV-infected patients. RESULTS: Two weeks after single PI therapy, the addition of TPV/r reduced plasma trough levels 52%, 80%, and 56% for lopinavir (LPV), saquinavir (SQV), and amprenavir (APV) recipients, respectively. After 2 weeks, a TPV/r-only regimen reduced HIV viral load (VL) by a median of 1.06 log(10) copies/mL. VL reductions at 2 weeks between single-boosted CPIs were difficult to compare, because the numbers of patients maintaining their previous failing PI after randomization were different. At week 4, patients initiating treatment with TPV-containing regimens sustained VL reduction (median decrease of 1.27 log(10) copies/mL). Patients adding TPV to regimens at week 2 achieved median reductions from a baseline of 1.19 log(10), 0.96 log(10), and 1.12 log(10) copies/mL at week 4 in dual-boosted LPV, SQV, and APV groups, respectively. At 24 weeks, VL reductions (median: -0.24 to -0.47 log(10) copies/mL) were comparable between treatment groups. CONCLUSIONS: The efficacy of a dual PI regimen depended on the presence of TPV, with additional recycled CPIs having limited activity, even in drug-resistant patient populations with plasma trough concentrations regarded as likely to be adequate in this study. No clear guidelines exist about ARV plasma trough concentrations in treatment-experienced patients, however.

Case-control exploration of relationships between early rash or liver toxicity and plasma concentrations of nevirapine and primary metabolites.

OBJECTIVE: This investigation measured trough nevirapine and five oxidative metabolite concentrations in plasma specimens collected from patients who exhibited a rash or liver function abnormality during the first 6 weeks of treatment. METHOD: Patient selection came from three clinical trials, totaling 1,357 patients, from which frozen specimens had been stored and were available for assay. The control patients were matched according to trial, steroid use, CD4 cell count, gender, race, and hepatitis B/C status. Observed plasma metabolite concentrations were compared using signed rank tests. RESULTS: A total of 49 case-control pairs were studied. Women had significantly greater exposure than men to nevirapine and four of the five metabolites at week 2, but the plasma concentrations were comparable by week 4. Steroid (prednisone) co-medication produced significantly different plasma nevirapine and metabolite concentrations for the majority of case-control comparisons at week 3, a week after cessation of steroid treatment, but only occasionally produced a measurable difference at other weeks. CONCLUSION: During the first 6 weeks of nevirapine therapy, the rashes and liver enzyme elevations that occurred appear to be idiosyncratic. There were no strong relationships observed between the plasma concentrations of nevirapine or any of its five metabolites to a casedefining event. The systemic exposure of the metabolite 12-hydroxynevirapine and its successor 4-carboxynevirapine, hypothesized in the skin rash female Brown Norway rat model as reactive intermediates for idiosyncratic immune-mediated adverse reactions, were comparable between case and control samples and were comparable in proportion to the precursor nevirapine exposure.

Quantitation of five nevirapine oxidative metabolites in human plasma using liquid chromatography-tandem mass spectrometry.

A multiple-reaction-monitoring LC/MS/MS method for the analysis of nevirapine oxidative metabolites, 2-hydroxynevirapine, 3-hydroxynevirapine, 8-hydroxynevirapine, 12-hydroxynevirapine, and 4-carboxynevirapine, in human plasma was developed and validated. The metabolites were isolated from 50 microL heparinized plasma by enzymatic hydrolysis of the glucuronide conjugates to the free metabolite followed by protein precipitation with acetonitrile. Peaks were quantitated at 3.03 min for the 4-carboxynevirapine metabolite, at 3.72, 4.27, 5.27, and 5.73 min for the positional 2-hydroxynevirapine, 12-hydroxynevirapine, 3-hydroxynevirapine, and 8-hydroxynevirapine metabolites, respectively, and 2.30 min for the internal standard, pirenzepine. The assay was accurate and precise based on assay validation controls over the nominal range of 0.010-1.0 mg/L. The average accuracy at the lowest concentration quality control (QC) sample was 16% (difference from theoretical value) for 8-hydroxynevirapine, all others were closer to their known respective standards. Within- and between-day precisions were within 12% for quality control samples for all five metabolites. Repetitive thawing and freezing did not have an effect on any metabolite through a minimum of three cycles. Thawed samples, remaining in plasma for 4 h before extraction, were within 5% of theoretical value. Stability of the extracted samples on the autosampler at room temperature was evaluated for 48 h and was observed to be within 12% of a fresh analytical sample for 2-hydroxynevirapine and 3-hydroxynevirapine; other metabolites were within 6% of theoretical value. The utility of the analytical method was demonstrated using trough steady-state plasma samples collected from 48 patients in a hepatic impairment study.

Steady-state disposition of the nonpeptidic protease inhibitor tipranavir when coadministered with ritonavir.

The pharmacokinetic and metabolite profiles of the antiretroviral agent tipranavir (TPV), administered with ritonavir (RTV), in nine healthy male volunteers were characterized. Subjects received 500-mg TPV capsules with 200-mg RTV capsules twice daily for 6 days. They then received a single oral dose of 551 mg of TPV containing 90 microCi of [(14)C]TPV with 200 mg of RTV on day 7, followed by twice-daily doses of unlabeled 500-mg TPV with 200 mg of RTV for up to 20 days. Blood, urine, and feces were collected for mass balance and metabolite profiling. Metabolite profiling and identification was performed using a flow scintillation analyzer in conjunction with liquid chromatography-tandem mass spectrometry. The median recovery of radioactivity was 87.1%, with 82.3% of the total recovered radioactivity excreted in the feces and less than 5% recovered from urine. Most radioactivity was excreted within 24 to 96 h after the dose of [(14)C]TPV. Radioactivity in blood was associated primarily with plasma rather than red blood cells. Unchanged TPV accounted for 98.4 to 99.7% of plasma radioactivity. Similarly, the most common form of radioactivity excreted in feces was unchanged TPV, accounting for a mean of 79.9% of fecal radioactivity. The most abundant metabolite in feces was a hydroxyl metabolite, H-1, which accounted for 4.9% of fecal radioactivity. TPV glucuronide metabolite H-3 was the most abundant of the drug-related components in urine, corresponding to 11% of urine radioactivity. In conclusion, after the coadministration of TPV and RTV, unchanged TPV represented the primary form of circulating and excreted TPV and the primary extraction route was via the feces.

Pharmacokinetics of nevirapine: once-daily versus twice-daily dosing in the 2NN study.

OBJECTIVE: As part of the large international, randomized 2NN trial, the pharmacokinetics of nevirapine in once-daily 400 mg and twice-daily 200 mg dosing regimens were investigated. METHOD: Treatment-naive HIV-1-infected patients were randomized to receive nevirapine 400 mg once daily or 200 mg twice daily, in combination with lamivudine and stavudine. Blood samples were collected at several time-points (day 3, weeks 1, 2, 4, 24, and 48). Differences in pharmacokinetics between once- versus twice-daily dosing were investigated with nonlinear mixed effects modelling (NONMEM). RESULTS: In total, 2,899 nevirapine plasma concentrations were available from 578 patients. Dosage and dosing frequency did not influence clearance or volume of distribution of nevirapine, indicating linear pharmacokinetic behavior of nevirapine whether given as a single daily dose or as divided doses over 24 hours. During steady state, the Cmin was lower (3.26 mg/L vs. 4.44 mg/L; p < .001) and the Cmax was higher (7.88 mg/L vs. 6.55 mg/L; p < .001) in the once-daily arm. However, compared to total variability in nevirapine levels for both treatments, these differences were minor. During steady state, total exposure, measured as AUC24h, was comparable for both regimens (133 mg/L*h vs. 133 mg/L*h; p = .084). CONCLUSION: The daily exposure to nevirapine (AUC24h) was similar for the 400 mg once-daily and the 200 mg twice-daily dosing regimens. The Cmin of nevirapine is lower and the Cmax of nevirapine is higher for the once-daily regimen as compared to the twice-daily regimen. As a result, 200 mg nevirapine dosed twice daily may be preferred over 400 mg nevirapine dosed once daily.

Are adverse events of nevirapine and efavirenz related to plasma concentrations?

OBJECTIVE: The relationships between adverse events (AEs) and plasma concentrations of nevirapine (NVP) and efavirenz (EFV) were investigated as part of the large, international, randomized 2NN study. METHODS: Treatment-naive, HIV-1-infected patients received NVP (once or twice daily), EFV or their combination, each in combination with lamivudine and stavudine. Blood samples were collected on day 3 and weeks 1, 2, 4, 24 and 48. Concentrations of NVP and EFV were quantitatively assessed by a validated HPLC assay. Individual Bayesian estimates of the area under the plasma concentration-time curve over 24 h (AUC24h), and minimum and maximum plasma concentrations (Cmin and Cmax) as measures for drug exposure of NVP and EFV, were generated using a previously developed population pharmacokinetic model. Pharmacokinetic parameters were compared for patients with and without central nervous system (CNS) and psychiatric AEs, hepatic events, liver enzyme elevations (LEEs) and rash. Furthermore, it was investigated whether a clear cut-off for a pharmacokinetic parameter could be identified above which the incidence of AEs was clearly increased. AEs were also related to demographic parameters and baseline characteristics. RESULTS: In total, from 1077 patients, NVP (3024 samples) and EFV (1694 samples) plasma concentrations and AE data (825 observations) were available. For all patients Cmin, Cmax and AUC24h were determined. When corrected for known covariates of gender, CD4 cell count at baseline, region, hepatitis coinfection and possible interactions between these factors, no significant associations between AEs and any tested exposure parameter of NVP was observed. Also, no target Cmin value, above which patients were at increased risk for AEs, could be established. On the other hand, geographical region, hepatitis coinfection, CD4 cell count and gender were found to be significantly related with the incidence of CNS and psychiatric AEs, hepatic events, LEEs and rash during the treatment with NVP. The occurrence of elevated liver enzymes during the first 6 weeks in the EFV-containing arm was significantly (P = 0.036) correlated to the exposure of EFV (Cmin). Only hepatitis coinfection impacted on LEEs during the first 6 weeks of treatment. With an EFV Cmin above 2.18 mg/l during the induction phase, patients were 4.4 (range 1.3-15.5) times more at risk for elevated liver enzymes. No other correlations between AEs and EFV pharmacokinetics or patient characteristics could be identified. CONCLUSIONS: Pharmacokinetic parameters of NVP did not have a relationship to AEs in the 2NN trial when corrected for known covariates. The value of periodical drug monitoring of NVP as a way to prevent toxicity is therefore limited. Treating physicians should instead focus on factors that are more predictive of AEs (gender, CD4 count and hepatitis coinfection). High EFV Cmin levels resulted in elevated liver enzyme values during the first 6 weeks of treatment. Regular measurement of EFV levels and liver enzymes at the start of therapy may therefore be advised.