Nevirapine In HIV-infected Patients Research Articles

Drug-drug interactions between bedaquiline and the antiretrovirals lopinavir/ritonavir and nevirapine in HIV-infected patients with drug-resistant TB.

Bedaquiline is a new anti-TB drug, which is metabolized by cytochrome P450 (CYP) 3A4. Concomitant ART is important for all HIV-infected patients treated for TB, but several antiretrovirals inhibit or induce CYP3A4. Single-dose drug-drug interaction studies found no significant interactions with nevirapine or lopinavir/ritonavir, but these findings could be misleading, especially because of bedaquiline's long terminal t1/2. We evaluated the effect of nevirapine and lopinavir/ritonavir on bedaquiline exposure. We conducted a parallel-group pharmacokinetic study of three groups of participants who were on bedaquiline as part of therapy for drug-resistant TB: no ART (HIV seronegative); nevirapine-based ART; and lopinavir/ritonavir-based ART. Non-compartmental analyses were done and exposure of bedaquiline and its M2 metabolite compared between the no-ART group and the two ART groups. We enrolled 48 participants: 17 in the no-ART group, 17 in the nevirapine group and 14 in the lopinavir/ritonavir group. The following median bedaquiline pharmacokinetic parameters were significantly higher in the lopinavir/ritonavir group than in the no-ART group: AUC(0-48) (67 002 versus 34 730 ng · h/mL; P = 0.003); Tmax (6 versus 4 h; P = 0.003); and t1/2 (55 versus 31 h; P = 0.004). On multivariate analysis, bedaquiline exposure was increased by lopinavir/ritonavir, male sex and time on bedaquiline. Bedaquiline exposure was not significantly different between the nevirapine group and the no-ART group. M2 metabolite exposure was not significantly different in either of the antiretroviral groups compared with the no-ART group. Lopinavir/ritonavir significantly increased bedaquiline exposure. The clinical significance of this interaction remains to be determined.

Chronic alcohol use affects therapeutic steady state plasma drug concentrations of stavudine, lamivudine and nevirapine in HIV-infected patients during 9 months follow up period: WHO AUDIT tool application

Chronic alcohol consumption is a common problem among the HIV-infected patients on HAART. The study determined the effect of chronic alcohol use on steady state plasma drug concentrations of stavudine (d4T), lamivudine (3TC) and nevirapine (NVP) in HIV-infected patients during the 9 months follow up period. It also determined whether there were some patients with undetectable plasma drug concentrations in their plasma during the follow up. A case control using repeated measures design with serial measurements model, where plasma drug concentrations were measured at 3 month intervals was used. Chronic alcohol-use using WHO AUDIT tool was used to screen patients. A total of 41 patients (21 alcohol group and 20 control group) were followed up for 9 months with blood sampling done at 3 month intervals. The Shimadzu Class-VPTM HPLC Chromatography data system version 6.1 equipment with UV detector was used to measure the plasma drug concentrations. Data was analyzed using SAS 2003 version 9.1 statistical package with repeated measures fixed the model and means were compared using the student t-test. The mean steady state plasma concentration of both d4T and 3TC in chronic alcohol use group were lower than in the control group all throughout the 9 months period of follow-up. The mean steady state plasma drug concentrations of NVP were higher in the alcohol group at 0 and 3 months and lower in the 6 and 9 months as compared to the control group. The mean total plasma NVP concentration was higher in the chronic alcohol group as compared to the control group and the difference was statistically significant (p≤0.05). However some patients had undetectable plasma drug concentrations despite of having ≥ 95 % adherence rate. Chronic alcohol use by the HIV-infected patients lowers the steady state plasma drug concentrations of d4T, 3TC and NVP in patients.

Guidelines for the use of extended-release nevirapine in HIV-infected patients

Introduction: Nevirapine (NVP) was the first non-nucleoside reverse transcriptase inhibitor (NNRTI) approved for the treatment of HIV infection and quickly became one of the most extensively used antiretrovirals (ARVs) worldwide. A new extended-formulation of the drug has now been FDA approved for once-daily use.Areas covered: Two recent, randomized and controlled clinical trials have established the clinical noninferiority of a new, extended-release formulation of NVP (NVP XR), in both treatment-naive and treatment-experienced patients. VERxVE demonstrated the noninferiority of NVP XR in treatment-naive patients. Treatment-experienced patients already stable on the NVP immediate-release formulation (NVP IR) were safely transitioned directly to NVP XR in the TRANxITION study.Expert opinion: The advantage of the extended release formulation of NVP is that it permits once-daily dosing, while demonstrating safety and efficacy results that are noninferior to that of the twice-daily formulation. It is expected that patients who are on NVP IR at present will consider switching to NVP XR to achieve regimen simplification by reducing their daily dosing and pill burden. In addition, treatment-naive patients who are considering starting on an NVP-based ARV regimen will probably transition to the extended-release formulation once they have successfully initiated NVP therapy according to current guidelines.

Safety and efficacy of tenofovir/emtricitabine plus nevirapine in HIV-infected patients

All 178 HIV-infected individuals who had initiated tenofovir-emtricitabine-nevirapine (TDF/FTC/NVP) at our institution and were adherent to their medication were retrospectively examined. Only 22% were antiretroviral naive. After a median follow-up of 16 months, only five (2.8%) individuals (all with prior exposure to other antiretroviral regimens) experienced virological failure. In all instances, viral rebound occurred after 12 weeks of therapy. These results do not support an increased risk of early virological failure using TDF/FTC/NVP.

Substrate Specificity, Regulation, and Polymorphism of Human Cytochrome P450 2B6

CYP2B6 is mainly expressed in the liver that has been thought historically to play an insignificant role in human drug metabolism. However, increased interest in this enzyme has been stimulated by the discovery of polymorphic and ethnic differences in CYP2B6 expression, identification of additional substrates for CYP2B6, and evidence for co-regulation with CYP3A4. This paper updates our knowledge about the structure, function, regulation and polymorphism of CYP2B6. CYP2B6 can metabolise approximately 8% of clinically used drugs (n > 60), including cyclophosphamide, ifosfamide, tamoxifen, ketamine, artemisinin, nevirapine, efavirenz, bupropion, sibutramine, and propofol. CYP2B6 is one of the CYP enzymes that bioactivate several procarcinogens and toxicants. This enzyme also metabolizes arachidonic acid, lauric acid, 17beta-estradiol, estrone, ethinylestradiol, and testosterone. Typical substrates of CYP2B6 are non-planar molecules, neutral or weakly basic, highly lipophilic with one or two hydrogen-bond acceptors. The crystal structure of CYP2B6 has not been resolved, while several pharmacophore and homology models of human CYP2B6 have been reported. Human CYP2B6 is closely regulated by constitutive androstane receptor (CAR/NR1I3) which can activate CYP2B6 expression upon ligand binding. Pregnane X receptor and glucocorticoid receptor also play a role in the regulation of CYP2B6. Induction of CYP2B6 may partially explain some clinical drug interactions observed. For example, coadministered carbamazepine decreases the systemic exposure of bupropion. There is a wide interindividual variability in the expression and activity of CYP2B6. Such a large variability is probably due to effects of genetic polymorphisms and exposure to drugs that are inducers or inhibitors of CYP2B6. To date, at least 28 allelic variants and some subvariants of CYP2B6 (*1B through *29) have been described and some of them have been shown to have important functional impact on drug clearance and drug response. For example, the efavirenz plasma levels in African-American subjects with the CYP2B6 homozygous 516T/T genotype are approximately 3-fold higher than individuals carrying the homozygous G/G genotype. The CYP2B6 516T/T genotype is associated with 1.7-fold greater plasma levels of nevirapine in HIV-infected patients. Smokers with the 1459C>T (R487C) variant of CYP2B6 may be more vulnerable to abstinence symptoms and relapse following treatment with bupropion as a smoking cessation agent. Further studies in the structure, function, regulation and polymorphism of CYP2B6 are warranted.

Assessment of Drug-Drug Interactions Between Tenofovir Disoproxil Fumarate and the Nonnucleoside Reverse Transcriptase Inhibitors Nevirapine and Efavirenz in HIV-Infected Patients

Tenofovir disoproxil fumarate (DF) has been studied in combination with efavirenz in healthy volunteers and no interaction was found. No data are available on the possible interaction of tenofovir DF with nevirapine and efavirenz in HIV-infected patients. In this study the combination of nevirapine 200 mg twice daily with tenofovir DF 300 mg once daily and nevirapine 400 mg once daily with tenofovir DF 300 mg once daily were compared with nevirapine twice daily or once daily without tenofovir DF in HIV-infected patients. Furthermore, the combination of efavirenz 600 mg and tenofovir DF 300 mg once daily was compared with use of efavirenz 600 mg once daily only. Data were retrospectively collected from routine therapeutic drug monitoring plasma samples. Nevirapine, efavirenz, and tenofovir plasma levels and tenofovir concentration ratios were analyzed. The concentration ratio represents the measured plasma concentration compared with the time-adjusted average concentration, as measured in a reference population. Six different groups were studied: 200 mg nevirapine twice daily, 400 mg nevirapine once daily, 600 mg efavirenz once daily, all without tenofovir DF (groups 1, 2, and 3, respectively), and the same groups with the drugs combined with tenofovir 300 mg once daily (groups 4, 5, and 6, respectively). Plasma samples were evaluable for 272, 18, 126, 32, 94, and 118 patients in the groups 1-6, respectively. No differences were found in plasma levels for tenofovir, nevirapine, and efavirenz for either of the combinations studied. Addition of tenofovir DF to efavirenz or nevirapine in HIV-infected patients does not influence the plasma levels of nevirapine or efavirenz. Furthermore, nevirapine and efavirenz have no effect on tenofovir plasma levels or tenofovir concentration ratios. Efavirenz or nevirapine can be coadministered with tenofovir DF in HIV-infected patients without dose modifications.

Comparison of efavirenz and nevirapine in HIV-infected patients (NEEF Cohort)

The non-nucleoside reverse transcriptase inhibitors (NNRTIs) efavirenz (EFV) and nevirapine (NVP) taken in combination with nucleoside reverse transcriptase inhibitors (NRTIs) have both shown to be just as highly effective as protease inhibitors (PIs) in reducing viral load in patients infected with HIV. Our study compares the performance of these two NNRTIs with each other. This was a non-randomized, prospective, two-arm, multi-centre trial. We evaluated all patients with an EFV- or NVP-containing antiretroviral regimen. The primary endpoint was the difference in success rates defined as a viral load of </=50 copies/mL at week 48. chi(2)-tests were used for naïve and pretreated patients using intention-to-treat (ITT) and on-treatment analysis. As secondary endpoints, a viral load of </=500 copies/mL and CD4 count at week 48 for naïve patients were evaluated. A Cox regression was used to adjust for prespecified covariates. We included 662 patients (NVP 337, EFV 325). The difference in success rates in the ITT analysis was 4.5% ( -11.5%, 19.0%), P=0.578. Pretreated patients with a triple therapy show a difference of 10.1 (-0.3, 20.6), P=0.056. Non-significant results appeared for all secondary analyses. In this trial, no difference between EFV and NVP in combination with NRTI backbone therapy can be shown, regarding viral load. Further randomized studies are necessary to evaluate possible differences.

Influence of CYP2B6 polymorphism on plasma and intracellular concentrations and toxicity of efavirenz and nevirapine in HIV-infected patients

Efavirenz (EFV) and nevirapine (NVP) are metabolized by cytochrome P450 2B6 (CYP2B6). Allele 516 G>T (Gln172His) is associated with diminished activity of this isoenzyme, and may lead to differences in drug exposure. We evaluated this allele as a pharmacogenetic marker of EFV and NVP pharmacokinetics and EFV toxicity in 167 participants receiving EFV and 59 receiving NVP recruited within the genetics project of the Swiss HIV Cohort Study. Drug concentrations were measured in plasma and in peripheral blood mononuclear cells (PBMCs) from the same sample. Neuropsychological toxicity of EFV (sleep disorders, mood disorders, fatigue) was assessed using a standardized questionnaire. CYP2B6 516TT was associated with greater plasma and intracellular exposure to EFV, and greater plasma exposure to NVP. Intracellular drug concentration, and CYP2B6 genotype were predictors of EFV neuropsychological toxicity. CYP2B6 genotyping may be useful to complement an individualization strategy based on plasma drug determinations to increase the safety and tolerability of EFV.