The influence of tuberculosis treatment on efavirenz clearance in patients co-infected with HIV and tuberculosis

Pharmacokinetics of Efavirenz 600mg in Combination with Rifampicin in Chinese HIV/TB Co-Infection Patients

Background

Rifampicin is a known inducer of the cytochrome P450 (CYP2B6) enzyme, which can lead to a decrease in the concentration of efavirenz. Therefore, we conducted a study to evaluate the effect of daily rifampicin intake on efavirenz 600mg pharmacokinetics and HIV-1 virological suppression.

Methods

Patients receiving antiretroviral therapy containing efavirenz (600mg daily), and we collected efavirenz concentration at four visit points: ART day 14 (PK1), ART day 42 (PK2), ART day 140 (PK3), and ART day 336 (PK4), and performed pharmacokinetics analysis.

Results

From February 2017 to November 2020, 29 HIV/TB co-infection patients were included. Ninety percent of patients had a concentration of ≥1000ng/mL of efavirenz during the study. All patients had efavirenz C_max ≥1000ng/mL, 86% patients showed good virology response.

Conclusion

Our study shows that the use of rifampicin in HIV/TB co-infection patients does not affect efavirenz drug concentrations, that virological suppression is good and that no efavirenz dose adjustment is required.

Effects of rifampicin, CYP2B6 and ABCB1 polymorphisms on efavirenz plasma concentration in Chinese patients living with HIV and tuberculosis

BACKGROUND

Tuberculosis (TB) is the leading opportunistic infection of people living with human immunodeficiency virus (HIV; PLWH). Cytochrome P450 (CYP) 2B6 and ATP-binding cassette sub-family B member 1 (ABCB1) are involved in the metabolism and transportation of efavirenz. The study was aimed to investigate the effects of rifampicin, CYP2B6 and ABCB1 polymorphisms on efavirenz exposure in Chinese PLWH co-infected with TB.

METHOD

PLWH were screened according to inclusion and exclusion criteria and divided into HIV group and HIV/TB group. Efavirenz plasma concentration (C₀) was determined, dose-adjusted concentration (C₀/D) was calculated, and genotypes of CYP2B6 516G>T, 785A>G, and ABCB1 2677G>T, 3435C>T were analyzed.

RESULTS

252 PLWH were enrolled, including 75 co-infected with TB and concomitant with rifampicin. Efavirenz C₀ and C₀/D were both higher in HIV group (1.94 μg/mL, 0.2007 (μg/ml)/(mg/kg/d)) compared with HIV/TB group (1.52 μg/mL, 0.1557 (μg/ml)/(mg/kg/d)) (p = .001). Efavirenz C₀/D was significantly higher in patients with variant genotypes of CYP2B6 516G>T and 785A>G (p<.001), and was significantly lower in HIV/TB group compared with HIV group among patients with CYP2B6 516 GG, TT, and 785 AA, AG genotypes (p < .05).

CONCLUSION

Efavirenz exposure is reduced by co-administration with rifampicin, and related to genetic polymorphisms of CYP2B6.

Constitutive androstane receptor and pregnane X receptor genotype influence efavirenz plasma concentration and CYP2B6 enzyme activity

Efavirenz is metabolized by CYP2B6, an inducible enzyme whose expression is regulated by the constitutive androstane receptor and pregnane X receptor nuclear receptors. CAR and PXR are encoded by genetically polymorphic NR1I2 and NR1I3, respectively. We examined the impact of NR1I2 and NR1I3 genotype on plasma EFV concentration and CYP2B6 enzyme activity among TB-HIV co-infected patients in Ethiopia. Treatment-naïve HIV patients with TB co-infection (n = 80) were enrolled and received first-line EFV-based antiretroviral and rifampicin-based anti-TB therapy. Plasma EFV and 8-hydroxy-EFV concentrations at the 4th and 16th week of EFV treatment were determined using LC/MS/MS. EFV/8-hydroxy-EFVmetabolic ratio was used as CYP2B6 metabolic activity index. In multivariate regression analysis, NR1I3 rs3003596C or NR1I2 rs2472677T variant allele carriers had significantly lower plasma EFV concentrations than non-carriers. Patients with NR1I2 rs3814057C/C genotype or NR1I3 rs3003596C allele carriers had significantly lower mean log EFV MR. Among CYP2B6*6 allele carriers, patients with NR1I3 rs2502815T/T or NR1I2 rs3814057C/C genotype had significantly lower mean log EFV MR. In conclusion, genetic variants in NR1I2 and NR1I3 genes influence plasma EFV exposure and CYP2B6 enzyme activity in TB-HIV co-infected patients on drug treatment.

Impact of CYP2B6 genotype, tuberculosis therapy, and formulation on efavirenz pharmacokinetics in infants and children under 40 months of age

OBJECTIVE

Dosing efavirenz (EFV) in children less than 3 years of age is challenging due to large variability in drug levels. This study evaluated differences in pharmacokinetics with tuberculosis (TB) therapy, formulation, age, and CYP2B6 genotype.

DESIGN

Pharmacokinetic data from three IMPAACT/PACTG studies (P382, P1021, and P1070) for children initiating therapy less than 40 months of age were evaluated.

METHODS

Pharmacokinetic data were combined in a population pharmacokinetic model. Exposure from the 2-week pharmacokinetic visit was compared with changes in viral RNA between the Week 0 and Week 4 visits.

RESULTS

The model included 103 participants (19 on TB therapy). CYP2B6 516 genotype information was available for 82 participants (TT: 15, GT: 28, GG: 39). Median age at the first pharmacokinetic visit was 17.0 months (range: 2.0-39.0 months). Liquid formulation led to a 42% decrease in bioavailability compared with opened capsules. TB therapy (isoniazid and rifampin) led to a 29% decreased clearance, however Monte Carlo simulations demonstrated the majority of participants on TB therapy receiving standard EFV dosing to be in the target area under the curve range. Clearance was 5.3-fold higher for GG than TT genotype and 3.3-fold higher for GT than TT genotype. Age did not have a significant effect on clearance in the final model. Initial viral RNA decay was lower for patients in the lowest quartile of exposures (area under the curves) than for higher quartiles (P = 0.013).

CONCLUSION

EFV dosing should account for CYP2B6 516 genotype and formulation, but does not require adjustment for concurrent TB therapy.

Analysis of Potential Interaction between Antiretrovirals and Comorbid Medications of HIV Patients at a Top Referral Hospital in Indonesia

Background:

HIV/AIDS usually present with comorbid diseases such as tuberculosis, pneumonia, toxoplasmosis, fungal infections, etc., that need multiple medications. Potential interaction between ARV and comorbid drugs is unavoidable.

Objective:

This study aimed to investigate the potential interaction between ARV drugs and medications used to treat comorbid diseases among HIV patients at the Dr. Cipto Mangunkusumo Hospital, Jakarta.

Methods:

This was an observational study using medical record data of 121 HIV/AIDS patients treated at the CM Hospital between January 2016 and July 2017. Potential interaction was classified as “major” if it could lead to increase or decrease of plasma drug levels which potentially result in either drug toxicity or treatment failure, or clinically significant harm to the patient; “moderate” if the interaction is not major, but with the recommendation of close monitoring. National, European, Australian, and Liverpool iChart guidelines were used for the classification of drug interactions.

Results:

Major interactions were noted in 17 (14.05%)patients. Fourteen of them received rifampicin, which potentially decreases plasma level of nevirapine (9 patients), rilpivirine (1 patient), and lopinavir/ritonavir (4 patients). Potential increase of ARV level was found in 3 patients involving interaction between voriconazole-efavirenz (2) and omeprazole-rilpivirine (1). Moderate interaction with the potential decrease of ARV level occurred in 46 patients (38.01%); consisting of a combination of rifampicin with efavirenz (38 pts), rifampicin with zidovudine (6 pts), and phenytoin with efavirenz or nevirapine (2 patients).

Conclusion:

Potential major interaction occurred in 17 (14.05%), which mostly attributed to rifampicin use; while moderate interaction occurred in 46 (38.01%) of patients. Although no serious adverse event was observed in this study, special care should be taken when the drugs with potential major interaction are to be administered

Pharmacokinetics of Efavirenz 400 mg Once Daily Coadministered With Isoniazid and Rifampicin in Human Immunodeficiency Virus-Infected Individuals

Background

The World Health Organization recommends efavirenz 400 mg (EFV400) as first-line antiretroviral therapy, with a disclaimer that no data with anti-tuberculosis (TB) treatment exist. Many people living with human immunodeficiency virus (PLWH) require TB treatment with isoniazid (INH) and rifampicin (RIF), which affect cytochrome P450 and antiretroviral exposure.

Methods

PLWH receiving tenofovir disoproxil fumarate (TDF)/emtricitabine (FTC)/EFV 600 mg with a viral load (VL) <50 copies/mL switched to TDF/FTC/EFV400. Genetic polymorphisms and pharmacokinetic (PK) parameters of EFV400 without (PK1) and with INH/RIF following 4 (PK2) and 12 (PK3) weeks of coadministration were evaluated.

Results

Twenty-six PLWH were enrolled; 22 completed PK2. All maintained VL <50 copies/mL throughout the study. Geometric mean ratio (GMR) PK2/PK1 of EFV400 maximum plasma concentration (Cmax), area under the curve (AUC), and concentration at 24 hours postdose (C24h) were 0.91 (90% confidence interval [CI], .83-.99), 0.91 (90% CI, .79-1.05), and 0.85 (90% CI, .72-.99), respectively. GMRs (90% CI) of PK3/PK2 and PK3/PK1 Cmax, AUC, and C24h were 0.95 (.86-1.05) and 0.92 (.83-1.01), 0.88 (.75-1.03) and 0.84 (.75-.93), and 0.84 (.72-.99) and 0.75 (.62-.92), respectively. Eleven of 22 participants carried polymorphisms in the CYP2B6 gene associated with slow EFV metabolism.

Conclusions

INH/RIF coadministration was associated with limited changes in EFV400 AUC (<25%), and EFV400 concentrations were maintained within ranges of those measured in PLWH in the ENCORE-1 study, irrespective of CYP2B6 genotype. The coadministration of EFV400 with anti-TB treatment can be considered and this is being confirmed in PLWH with TB.

Clinical Trials Registration

NCT02832778.

Impact of Population and Pharmacogenetics Variations on Efavirenz Pharmacokinetics and Immunologic Outcomes During Anti-Tuberculosis Co-Therapy: A Parallel Prospective Cohort Study in Two Sub-Sahara African Populations

Efavirenz-based combination antiretroviral-therapy (cART) is the recommended regimen during tuberculosis (TB) therapy. In a multi-national parallel prospective-cohort study, we investigated the impact of population and pharmacogenetic variations for efavirenz pharmacokinetics, auto-induction, and immunologic outcome during antituberculosis treatment. A total of 921 treatment-naïve HIV patients with (196 Ethiopians and 231 Tanzanians) or without TB co-infection (285 Ethiopians and 209 Tanzanians) were enrolled and treated with efavirenz-based cART. TB-HIV patients started rifampicin-based anti-TB therapy 4 weeks before cART. Efavirenz plasma concentrations were measured on the 4th and 16th weeks of cART. Genotyping for CYP2B6, CYP3A5, ABCB1, UGT2B7, and SLCO1B1 was done. CD4 cells-count was measured at baseline, 12th, 24th, and 48th weeks of cART. Among HIV-only cohort, plasma efavirenz concentration and median CD4 cell count were significantly higher in Tanzanians than Ethiopians, and both CYP2B6 genotype and population-variation were significant predictors of efavirenz plasma concentration. Within-population analyses indicated a pronounced efavirenz autoinduction in Tanzanians as reflected by a significant decrease of plasma efavirenz concentration over time (p = 0.0001), but not in Ethiopians. Among TB-HIV cohort, there were no significant between-population differences in plasma efavirenz concentrations or CD4 cell-recovery, and CYP2B6 genotype but not population-variation was a significant predictor of efavirenz plasma exposure. In Tanzanian patients, short-term anti-TB co-treatment significantly reduced the mean plasma efavirenz concentration in CYP2B6*1/*1 genotype at week-4 (p = 0.005), but not at week-16 of cART. In Ethiopian patients, anti-TB cotreatment increased the mean plasma efavirenz concentration among CYP2B6*6 carriers at week-4 (p = 0.003) and week-16 (p = 0.035) of cART. In general, long-term anti-TB co-treatment increased plasma efavirenz concentration at week 16 of cART in both Ethiopians and Tanzanians being higher in CYP2B6*6/*6 > *1/*6 > *1/*1 genotypes. In TB-HIV patients, baseline body mass index (BMI), viral load, and WHO clinical-stage but not genotype, population-variation, or efavirenz concentration were significant predictors of immunologic outcome at week-48. In summary efavirenz auto-induction, pharmacokinetics, and the immunologic outcome are influenced by population-variation, anti-TB co-medication, and CYP2B6 genotype. CYP2B6 genotype is a significant predictor of efavirenz plasma exposure regardless of population-variation or antituberculosis co-treatment, but population-variation is insignificant during antituberculosis treatment. CYP2B6 genotype, population, and geographic differences need to be considered for efavirenz dosage-optimization.

Safety implications of combined antiretroviral and anti-tuberculosis drugs

Introduction: Antiretroviral and anti-tuberculosis (TB) drugs are often co-administered in people living with HIV (PLWH). Early initiation of antiretroviral therapy (ART) during TB treatment improves survival in patients with advanced HIV disease. However, safety concerns related to clinically significant changes in drug exposure resulting from drug-drug interactions, development of overlapping toxicities and specific challenges related to co-administration during pregnancy represent barriers to successful combined treatment for HIV and TB.Areas covered: Pharmacokinetic interactions of different classes of ART when combined with anti-TB drugs used for sensitive-, drug-resistant (DR) and latent TB are discussed. Overlapping drug toxicities, implications of immune reconstitution inflammatory syndrome (IRIS), safety in pregnancy and research gaps are also explored.Expert opinion: New antiretroviral and anti-tuberculosis drugs have been recently introduced and international guidelines updated. A number of effective molecules and clinical data are now available to build treatment regimens for PLWH with latent or active TB. Adopting a systematic approach that also takes into account the need for individualized variations based on the available evidence is the key to successfully integrate ART and TB treatment and improve treatment outcomes.

Detection of Tuberculosis Recurrence, Diagnosis and Treatment Response by a Blood Transcriptomic Risk Signature in HIV-Infected Persons on Antiretroviral Therapy

HIV-infected individuals are at high risk of tuberculosis disease and those with prior tuberculosis episodes are at even higher risk of disease recurrence. A non-sputum biomarker that identifies individuals at highest tuberculosis risk would allow targeted microbiological testing and appropriate treatment and also guide need for prolonged therapy. We determined the utility of a previously developed whole blood transcriptomic correlate of risk (COR) signature for (1) predicting incident recurrent tuberculosis, (2) tuberculosis diagnosis and (3) its potential utility for tuberculosis treatment monitoring in HIV-infected individuals. We retrieved cryopreserved blood specimens from three previously completed clinical studies and measured the COR signature by quantitative microfluidic real-time-PCR. The signature differentiated recurrent tuberculosis progressors from non-progressors within 3 months of diagnosis with an area under the Receiver-operating characteristic (ROC) curve (AUC) of 0.72 (95% confidence interval (CI), 0.58-0.85) amongst HIV-infected individuals on antiretroviral therapy (ART). Twenty-five of 43 progressors (58%) were asymptomatic at microbiological diagnosis and thus had subclinical disease. The signature showed excellent diagnostic discrimination between HIV-uninfected tuberculosis cases and controls (AUC 0.97; 95%CI 0.94-1). Performance was lower in HIV-infected individuals (AUC 0.83; 95%CI 0.81-0.96) and signature scores were directly associated with HIV viral loads. Tuberculosis treatment response in HIV-infected individuals on ART with a new recurrent tuberculosis diagnosis was also assessed. Signature scores decreased significantly during treatment. However, pre-treatment scores could not differentiate between those who became sputum negative before and after 2 months. Direct application of the unmodified blood transcriptomic COR signature detected subclinical and active tuberculosis by blind validation in HIV-infected individuals. However, prognostic performance for recurrent tuberculosis, and performance as diagnostic and as treatment monitoring tool in HIV-infected persons was inferior to published results from HIV-negative cohorts. Our results suggest that performance of transcriptomic signatures comprising interferon stimulated genes are negatively affected in HIV-infected individuals, especially in those with incompletely suppressed viral loads.

Drug-Drug Interactions of Infectious Disease Treatments in Low-Income Countries: A Neglected Topic?

Despite recent advances in recognizing and reducing the risk of drug-drug interactions (DDIs) in developed countries, there are still significant challenges in managing DDIs in low-income countries (LICs) worldwide. In the treatment of major infectious diseases in these regions, multiple factors contribute to ineffective management of DDIs that lead to loss of efficacy or increased risk of adverse events to patients. Some of these difficulties, however, can be overcome. This review aims to evaluate the inherent complexities of DDI management in LICs from pharmacological standpoints and illustrate the unique barriers to effective management of DDIs, such as the challenges of co-infection and treatment settings. A better understanding of comprehensive drug-related properties, population-specific attributes, such as physiological changes associated with infectious diseases, and the use of modeling and simulation techniques are discussed, as they can facilitate the implementation of optimal treatments for infectious diseases at the individual patient level.

Cytochrome P450 CYP2B6*6 distribution among Congolese individuals with HIV, Tuberculosis and Malaria infection

BACKGROUND

The cytochrome P450 CYP2B6*6 (CYP2B6 c.516G>T; rs3745274) is one of the genetic factors that alters the drug metabolism in antimalarial, antiretroviral and TB first-line drugs. In Central African populations, the distribution of the CYP2B6*6 variant is poorly documented. This study investigated the distribution of CYP2B6 c.516G>T variant among Congolese individuals.

METHODS

A total of 418 patients with HIV-1 mono-infection, HIV-1 and Tuberculosis coinfection and symptomatic P. falciparum malaria were genotyped for the CYP2B6 c.516G>T SNP using Restriction Fragment Length Polymorphism (RFLP). The allele frequencies and genotype distributions were determined.

RESULTS

The CYP2B6 c.516G>T was successfully analysed in 69% (288/418) of the study participants. Among the investigated individuals, the distribution of the major allele CYP2B6*G was 45% and the minor CYP2B6*T allele was 55%. Significant differences in genotype distribution were also observed among the studied individuals. The CYP2B6*GG (rapid metabolizer) genotype was observed in 17% (49/288) followed by CYP2B6*GT (intermediate metabolizer) 55% (159/288) and CYP2B6*TT (poor metabolizers) 28% (80/288).

CONCLUSION

This study contributes to increasing understanding on population pharmacogenetics and may help policy makers regulate treatment guidelines in the Congolese population with a high burden of HIV, Malaria and TB.

Conference report: pharmacogenomics in special populations at WCP2018

The 18th World Congress of Basic and Clinical Pharmacology (WCP2018), coordinated by IUPHAR and hosted by the Japanese Pharmacological Society and the Japanese Society of Clinical Pharmacology and Therapeutics, was held in July 2018 at the Kyoto International Conference Center, in Kyoto, Japan. Having as its main theme 'Pharmacology for the Future: Science, Drug Development and Therapeutics', WCP2018 was attended by over 4500 delegates, representing 78 countries. The present report is an overview of a symposium at WCP2018, entitled Pharmacogenomics in Special Populations, organized by IUPHAR´s Pharmacogenetics/Genomics (PGx) section. The PGx section congregates distinguished scientists from different continents, covering expertise from basic research, to clinical implementation and ethical aspects of PGx, and one of its major activities is the coordination of symposia and workshops to foster exchange of PGx knowledge (https://iuphar.org/sections-subcoms/pharmacogenetics-genomics/). The symposium attracted a large audience to listen to presentations covering various areas of research and clinical adoption of PGx in Oceania, Africa, Latin America and Asia.

Long-term efavirenz pharmacokinetics is comparable between Tanzanian HIV and HIV/Tuberculosis patients with the same CYP2B6*6 genotype

The impact of anti-tuberculosis co-treatment on efavirenz (EFV) exposure is still uncertain as contradictory reports exist, and the relevance of CYP2B6*6 genetic polymorphism on efavirenz clearance while on-and-off anti-tuberculosis co-treatment is not well investigated. We investigated the determinants of long-term efavirenz pharmacokinetics by enrolling HIV (n = 20) and HIV/Tuberculosis (n = 36) subjects undergoing efavirenz and efavirenz/rifampicin co-treatment respectively. Pharmacokinetic samplings were done 16 weeks after initiation of efavirenz-based anti-retroviral therapy and eight weeks after completion of rifampicin-based anti-tuberculosis treatment. Population pharmacokinetic modeling was used to characterize variabilities and covariates of efavirenz pharmacokinetic parameters. CYP2B6*6 genetic polymorphism but not rifampicin co-treatment was the statistically significant covariate. The estimated typical efavirenz clearance in the HIV only subjects with the CYP2B6*1/*1 genotype was 23.6 L/h/70 kg, while it was 38% and 69% lower in subjects with the CYP2B6*1/*6 and *6/*6 genotypes, respectively. Among subjects with the same CYP2B6 genotypes, efavirenz clearances were comparable between HIV and HIV/Tuberculosis subjects. Typical efavirenz clearances before and after completion of anti-tuberculosis therapy were comparable. In conclusion, after 16 weeks of treatment, efavirenz clearance is comparable between HIV and HIV/Tuberculosis patients with the same CYP2B6 genotype. CYP2B6 genotyping but not anti-tuberculosis co-treatment should guide efavirenz dosing to optimize treatment outcomes.

Plasma Cytokine Predictors of Tuberculosis Recurrence in Antiretroviral-Treated Human Immunodeficiency Virus-infected Individuals from Durban, South Africa

Background

Immune correlates of tuberculosis (TB) risk in populations infected with human immunodeficiency virus (HIV) remain understudied, despite HIV being associated with a high burden of TB disease. Here we describe plasma cytokine correlates of TB recurrence in a well-characterized cohort of HIV-infected individuals on antiretroviral therapy (ART) with a history of prior TB cure.

Methods

Study participants were drawn from a prospective cohort study initiated at the conclusion of a randomized clinical trial in which individuals presented with untreated HIV infection and active pulmonary TB. At baseline, ART was initiated, and TB successfully cured. Participants were screened for TB recurrence quarterly for up to 4 years. TB recurrent cases (n = 63) were matched to controls (n = 123) on sex, study arm assignment in the original trial, and month of enrollment with a subset of cases sampled longitudinally at several time-points.

Results

Three cytokines were associated with increased rates of TB recurrence in univariate models: interleukin 6 (IL6) (odds ratio [OR] 2.66, 95% confidence interval [CI] 1.34-5.28, P = .005), IP10 (OR 4.62, 95% CI 1.69-12.65, P = .003), monokine induced by IFN-γ (MIG) (OR 3.11, 95% CI 1.10-8.82, P = .034). Conversely, interferon β (IFNβ) was associated with decreased TB risk (OR 0.34, 95% CI 0.13-0.87, P = .025). Following multivariate analyses adjusting for covariates IL6, interleukin 1β (IL1β), and interleukin 1Rα (IL1Rα) were associated with increased risk and IFNβ with decreased TB risk. Longitudinal analysis showed that levels of many TB-associated markers, including IL6, IP10, sCD14, and interferon γ (IFNγ) are reduced following TB treatment.

Conclusion

These data show that TB recurrence, in HIV-infected individuals on ART is predicted by biomarkers of systemic inflammation, many of which are implicated in more rapid HIV disease progression.

Clinical Trials Registration

NCT 01539005.

Pharmacokinetics of efavirenz in patients on antituberculosis treatment in high human immunodeficiency virus and tuberculosis burden countries: A systematic review

AIMS

Efavirenz (EFV) and rifampicin-isoniazid (RH) are cornerstone drugs in human immunodeficiency virus (HIV)-tuberculosis (TB) coinfection treatment but with complex drug interactions, efficacy and safety challenges. We reviewed recent data on EFV and RH interaction in TB/HIV high-burden countries.

METHODS

We conducted a systematic review of studies conducted in the high TB/HIV-burden countries between 1990 and 2016 on EFV pharmacokinetics during RH coadministration in coinfected patients. Two reviewers conducted article screening and data collection.

RESULTS

Of 119 records retrieved, 22 were included (two conducted in children), reporting either EFV mid-dose or pre-dose concentrations. In 19 studies, median or mean concentrations of RH range between 1000 and 4000 ng ml^-1 , the so-called therapeutic range. The proportion of patients with subtherapeutic concentration of RH ranged between 3.1 and 72.2%, in 12 studies including one conducted in children. The proportion of patients with supratherapeutic concentration ranged from 19.6 to 48.0% in six adult studies and one child study. Five of eight studies reported virological suppression >80%. The association between any grade hepatic and central nervous system adverse effects with EFV/RH interaction was demonstrated in two and three studies, respectively. The frequency of the CYP2B6 516G > T polymorphism ranged from 10 to 28% and was associated with higher plasma EFV concentrations, irrespective of ethnicity.

CONCLUSIONS

Anti-TB drug coadministration minimally affect the EFV exposure, efficacy and safety among TB-HIV coinfected African and Asian patients. This supports the current 600 mg EFV dosing when coadministered with anti-TB drugs.

NeuroAIDS in children

The human immunodeficiency virus-1 (HIV-1) enters the central nervous system compartment within the first few weeks of systemic HIV infection and may cause a spectrum of neurologic complications. Without combination antiretroviral therapy (cART), 50-90% of all HIV-infected infants and children develop some form of neuroAIDS. Of the estimated 2.3 million children less than 15 years of age who were living in sub-Saharan Africa at the end of 2014, only 30% were receiving cART, suggesting that there is a large burden of neuroAIDS among HIV-infected children in sub-Saharan Africa. There is complex interplay between the disease process itself, the child's immune reaction to the disease, the secondary complications, the side-effects of antiretroviral drugs, and inadequate antiretroviral drug uptake into the central nervous system. In addition there is the layering effect from the multiple socioeconomic challenges for children living in low- and middle-income countries. Adolescents may manifest with a range of neurocognitive sequelae from mild neurocognitive disorder through to severe neurocognitive impairment. Neuroimaging studies on white-matter tracts have identified dysfunction, especially in the frontostriatal networks needed for executive function. Psychiatric symptoms of depression, attention deficit hyperactivity disorder, and behavioral problems are also commonly reported in this age group. Antiretroviral drugs may cause treatment-limiting neurologic and neuropsychiatric adverse reactions. The following chapter addresses the neurologic complications known to be, and suspected of being, associated with HIV infection in children and adolescents.

Nevirapine- versus Efavirenz-based antiretroviral therapy regimens in antiretroviral-naive patients with HIV and Tuberculosis infections in India: a multi-centre study

Background

According to World Health Organization (WHO) guidelines, which have also been adopted by the National AIDS Control Organization (NACO), India, Efavirenz-based Anti-Retroviral Therapy (ART) is better in Human-Immunodeficiency-Virus (HIV)-infected patients who are also being treated with Rifampicin-based Anti-Tuberculous Therapy (ATT). However, Efavirenz is much more expensive. We hypothesize that Nevirapine is a cheaper alternative that possesses equal efficacy as Efavirenz in HIV-Tuberculosis (TB) co-infected patients.

Methods

A parallel open-label randomized clinical trial was conducted at All India Institute of Medical Sciences (AIIMS), New Delhi and National AIDS Research Institute (NARI), Pune. Those who were ART-naïve and co-infected with TB were randomized to receive either Nevirapine (Group 1)- or Efavirenz (Group 2)-based ART along with Rifampicin-based ATT. ATT was begun first in ART-naïve patients according to the NACO guidelines, with a median of 27 days between ATT and ART in both groups. The primary endpoint was a composite unfavourable outcome (death and/or ART failure) at 96 weeks, and the secondary outcome was successful TB treatment at 48 weeks.

Results

A total of 284 patients (mean age 36.7 ± 8.1 years) were randomized in a 1:1 ratio to receive either Nevirapine (n = 144)- or Efavirenz (n = 140)-based ART after a median ATT-ART gap of 27 days. The median CD4 count was 105 cells/μl, with a median viral load of 820,200 copies/μl and no significant difference between the groups. Composite unfavourable outcomes were reported in 49 patients in the Nevirapine group and 51 patients in the Efavirenz group (35.3% vs. 36.9%; hazard ratio, 0.95, 95% confidence interval (CI), 0.63,1.43, adjusted). There was no difference in successful TB treatment outcome between the groups (71.5% vs. 65.6%, 95% CI -3.8,17.9, adjusted). The results were similar, showing no difference between the groups in the two centres of the study after adjusting for disease stage.

Conclusions

Composite unfavourable outcome in HIV-TB co-infected patients who were ART-naïve showed no statistically significant difference in the Nevirapine or Efavirenz groups.. Therefore, Nevirapine-based ART is a reasonable alternative to Efavirenz in resource-limited settings. However, multi-centric studies with larger sample sizes are required to confirm these findings.

Trial registration

NCT01805258 (Retrospectively registered on March 6, 2013) Date of registration: March 2013.

Electronic supplementary material

The online version of this article (10.1186/s12879-017-2864-0) contains supplementary material, which is available to authorized users.

Neuropsychiatric complications of efavirenz in children with HIV infection

Efavirenz is an effective antiretroviral agent widely used as part of first-line regimen in HIV1-infected children and adults. Neuropsychiatric adverse effects are reported in up to 50% of users. These include dizziness, insomnia, abnormal dreams, headache and impaired concentration. The plasma level of efavirenz may be key in the development of these adverse effects. Even among individuals taking recommended doses for weight, the plasma levels vary widely. Genetic polymorphisms leading to different allelic variants of the CYP2B6 enzyme, making some individuals slow metabolizers may play a role. These allelic variants are highest in people of African descent. This report examines the neuropsychiatric adverse effects of efavirenz, and the strength of the data that the product may result in neuronal damage.

Integrated therapy for HIV and tuberculosis

Tuberculosis (TB) has been the most common opportunistic infection and cause of mortality among HIV-infected patients, especially in resource-limited countries. Clinical manifestations of TB vary and depend on the degree of immunodeficiency. Sputum microscopy and culture with drug-susceptibility testing are recommended as a standard method for diagnosing active TB. TB-related mortality in HIV-infected patients is high especially during the first few months of treatment. Integrated therapy of both HIV and TB is feasible and efficient to control the diseases and yield better survival. Randomized clinical trials have shown that early initiation of antiretroviral therapy (ART) improves survival of HIV-infected patients with TB. A delay in initiating ART is common among patients referred from TB to HIV separate clinics and this delay may be associated with increased mortality risk. Integration of care for both HIV and TB using a single facility and a single healthcare provider to deliver care for both diseases is a successful model. For TB treatment, HIV-infected patients should receive at least the same regimens and duration of TB treatment as HIV-uninfected patients. Currently, a 2-month initial intensive phase of isoniazid, rifampin, pyrazinamide, and ethambutol, followed by 4 months of continuation phase of isoniazid and rifampin is considered as the standard treatment of drug-susceptible TB. ART should be initiated in all HIV-infected patients with TB, irrespective of CD4 cell count. The optimal timing to initiate ART is within the first 8 weeks of starting antituberculous treatment and within the first 2 weeks for patients who have CD4 cell counts <50 cells/mm(3). Non-nucleoside reverse transcriptase inhibitor (NNRTI)-based ART remains a first-line regimen for HIV-infected patients with TB in resource-limited settings. Although a standard dose of both efavirenz and nevirapine can be used, efavirenz is preferred because of more favorable treatment outcomes. In the settings where raltegravir is accessible, doubling the dose to 800 mg twice daily is recommended. Adverse reactions to either antituberculous or antiretroviral drugs, as well as immune reconstitution inflammatory syndrome, are common in patients receiving integrated therapy. Early recognition and appropriate management of these consequences can reinforce the successful integrated therapy in HIV-infected patients with TB.

CYP2B6 genotype, but not rifampicin-based anti-TB cotreatments, explains variability in long-term efavirenz plasma exposure

AIM

We investigated the effects of rifampicin-based anti-TB treatment on plasma efavirenz exposure and the implications of CYP2B6 genotype.

PATIENTS & METHODS

Antiretroviral therapy-naive Ugandan HIV patients without (n = 157) or with TB coinfection (n = 106) were enrolled and treated with efavirenz-based highly active antiretroviral therapy alone or with rifampicin-based anti-TB therapy, respectively. Efavirenz plasma concentration was determined on day 3 and weeks 1, 2, 8, 12, 16, 20, 24, 28 and 32.

RESULTS

Rifampicin-based anti-TB cotreatment reduced plasma efavirenz exposure during the first 2 weeks (p < 0.05), but no significant effect was observed afterwards. Although not significant, rifampicin-based anti-TB cotreatment inconsistently increased efavirenz exposure over time, which was reduced immediately after completing anti-TB therapy. CYP2B6*6, *11 and ABCB1 c.4036A>G genotypes were significant predictors of efavirenz plasma exposure.

CONCLUSION

Plasma efavirenz exposure is mainly influenced by CYP2B6 genotype, but not by rifampicin cotreatment. Therefore, no efavirenz dosage adjustment during rifampicin cotreatment is required in Ugandans.

Efavirenz dosing: influence of drug metabolizing enzyme polymorphisms and concurrent tuberculosis treatment

BACKGROUND

Rifampicin-based tuberculosis (TB) treatment alters efavirenz (EFV) clearance. Polymorphisms in important drug metabolizing enzymes and the implications for EFV dosing were investigated.

METHODS

Trough EFV concentrations (Cmin) were measured in 54 South African black patients. During TB treatment, EFV dose was 600 mg in patients <50 kg or 800 mg if ≥50 kg. Off TB treatment it was 600 mg. Polymorphisms in CYP2B6, CYP2A6 and UGT2B7 enzymes were sequenced. A multivariate generalized estimating equations model was fitted to assess predictors of high median EFV Cmin.

RESULTS

During TB treatment, median EFV Cmin was 3.2 (IQR 2.6-6.3) µg/ml and 3.3 (2.4-9.5) µg/ml in the 800 mg and 600 mg groups, respectively. After TB treatment EFV Cmin was 2.0 (1.4-3.5) µg/ml. Minor allele frequencies for CYP2B6 516G→T, 785A→G, 983T→C, UGT2B7-372G→A, CYP2A6*9B and CYP2A6*17 were 0.31, 0.33, 0.23, 0.29, 0.10 and 0.02, respectively. Haplotypes CYP2B6*6 and CYP2B6*18 were found in 38.9% and 25.9% of patients, respectively. Polymorphisms in all three CYP2B6 genes studied (516T-785G-983C) were present in 11.1% of patients and in this group median EFV Cmin was 19.2 (IQR 9.5-20) µg/ml during and 4.7 (IQR 3.5-5.6) µg/ml after TB treatment. The presence of TB treatment and composite genotypes CYP2B6 516 GT/TT, CYP2B6 983 TC/CC and CYP2A6*9B carrier status predicted median EFV Cmin>4 µg/ml. Adverse events due to high EFV concentrations were rare.

CONCLUSIONS

Because polymorphisms of EFV metabolizing enzymes are frequent and are associated with elevated EFV concentrations in this population, EFV dose increases are unnecessary when concomitant rifampicin-containing TB treatment is prescribed.

How to Choose In Vitro Systems to Predict In Vivo Drug Clearance: A System Pharmacology Perspective

The use of in vitro metabolism data to predict human clearance has become more significant in the current prediction of large scale drug clearance for all the drugs. The relevant information (in vitro metabolism data and in vivo human clearance values) of thirty-five drugs that satisfied the entry criteria of probe drugs was collated from the literature. Then the performance of different in vitro systems including Escherichia coli system, yeast system, lymphoblastoid system and baculovirus system is compared after in vitro-in vivo extrapolation. Baculovirus system, which can provide most of the data, has almost equal accuracy as the other systems in predicting clearance. And in most cases, baculovirus system has the smaller CV in scaling factors. Therefore, the baculovirus system can be recognized as the suitable system for the large scale drug clearance prediction.

Pharmacological interactions between rifampicin and antiretroviral drugs: challenges and research priorities for resource-limited settings

Coadministration of antituberculosis and antiretroviral therapy is often inevitable in high-burden countries where tuberculosis (TB) is the most common opportunistic infection associated with HIV/AIDS. Concurrent use of rifampicin and many antiretroviral drugs is complicated by pharmacokinetic drug-drug interactions. Rifampicin is a very potent enzyme inducer, which can result in subtherapeutic antiretroviral drug concentrations. In addition, TB drugs and antiretroviral drugs have additive (pharmacodynamic) interactions as reflected in overlapping adverse effect profiles. This review provides an overview of the pharmacological interactions between rifampicin-based TB treatment and antiretroviral drugs in adults living in resource-limited settings. Major progress has been made to evaluate the interactions between TB drugs and antiretroviral therapy; however, burning questions remain concerning nevirapine and efavirenz effectiveness during rifampicin-based TB treatment, treatment options for TB-HIV-coinfected patients with nonnucleoside reverse transcriptase inhibitor resistance or intolerance, and exact treatment or dosing schedules for vulnerable patients including children and pregnant women. The current research priorities can be addressed by maximizing the use of already existing data, creating new data by conducting clinical trials and prospective observational studies and to engage a lobby to make currently unavailable drugs available to those most in need.

Is there a need to increase the dose of efavirenz during concomitant rifampicin-based antituberculosis therapy in sub-Saharan Africa? The HIV-TB pharmagene study

AIMS

The current HIV treatment guidelines are inconsistent about the need for weight-based efavirenz dose adjustment during rifampicin containing antituberculosis (anti-TB) cotreatment. We investigated effect of rifampicin-based anti-TB cotreatment on plasma efavirenz exposure and treatment outcome, considering effect of CYP2B6 genotype and bodyweight.

PATIENTS & METHODS

HIV-only (arm 1, n = 285) or TB-HIV (arm 2, n = 208) coinfected patients were enrolled and received efavirenz-based ART alone or with rifampicin-based anti-TB therapy, respectively. Plasma efavirenz concentrations at 4th and 16th weeks, viral load and CD4 cell count at 24th and 48th weeks were determined.

RESULTS

The mean plasma efavirenz concentration at weeks 4 (p = 0.03) and 16 (p = 0.08) was inconsistently higher in arm 2 than arm 1, mainly in CYP2B6*6 carriers. Effect of bodyweight on efavirenz pharmacokinetics was significant only in arm 1, but not in arm 2. Proportion of patients with nondetectable viral load (≤50 copies/ml) at week 24 was higher in arm 1 than arm 2 patients (91.0 vs 76.3%; p = 0.002), but no significant difference was observed at week 48 (89.5 vs 87.8%; p = 0.22).

CONCLUSION

Rifampicin-based anti-TB cotreatment has no significant influence on long-term efavirenz plasma exposure and efficacy. Hence, there is no need to increase the dose of efavirenz during concomitant rifampicin-based anti-TB cotreatment in the sub-Saharan African population.

Combined effect of CYP2B6 and NAT2 genotype on plasma efavirenz exposure during rifampin-based antituberculosis therapy in the STRIDE study

In STRIDE, slow metabolizer CYP2B6 and NAT2 genotypes were each associated with increased plasma efavirenz concentrations during antituberculosis therapy. Concentrations were greater on therapy than off therapy in 58% with CYP2B6 and 93% with NAT2 slow metabolizer genotypes. Individuals with slow metabolizer genotypes in both genes had markedly elevated concentrations.

Nevirapine or efavirenz for tuberculosis and HIV coinfected patients: exposure and virological failure relationship

Objectives

We describe nevirapine and efavirenz exposure on and off tuberculosis treatment and consequences for virological efficacy and tolerance in patients included in the ANRS 12146/12214-CARINEMO trial.

Methods

Participants were randomly selected to receive either nevirapine at 200 mg twice daily (n = 256) or efavirenz at 600 mg daily (n = 270), both combined with two nucleoside analogues. Blood samples were drawn 12 h after nevirapine or efavirenz administration, while on tuberculosis treatment and after tuberculosis treatment discontinuation. In 62 participants, samples taken 12 h after drug administration were drawn weekly for the first month of ART. Sixteen participants participated in an extensive pharmacokinetic study of nevirapine. Concentrations were compared with the therapeutic ranges of 3000–8000 ng/mL for nevirapine and 1000–4000 ng/mL for efavirenz.

Results

Nevirapine concentrations at the end of the first week of treatment (on antituberculosis drugs) did not differ from concentrations off tuberculosis treatment, but declined thereafter. Concentrations at steady-state were 4111 ng/mL at week 12 versus 6095 ng/mL at week 48 (P < 0.0001). Nevirapine concentrations <3000 ng/mL were found to be a risk factor for virological failure. Efavirenz concentrations were higher on than off tuberculosis treatment (2700 versus 2450 ng/mL, P < 0.0001).

Conclusions

The omission of the 2 week lead-in dose of nevirapine prevented low concentrations at treatment initiation but did not prevent the risk of virological failure. Results support the WHO recommendation to use efavirenz at 600 mg daily in patients on rifampicin-based antituberculosis therapy.

Management of tuberculosis and latent tuberculosis infection in human immunodeficiency virus-infected persons

The syndemic of human immunodeficiency virus (HIV)/tuberculosis (TB) co-infection has grown as a result of the considerable sociogeographic overlaps between the two epidemics. The situation is particularly worrisome in countries with high or intermediate TB burden against the background of a variable HIV epidemic state. Early diagnosis of TB disease in an HIV-infected person is paramount but suffers from lack of sensitive and specific diagnostic tools. Enhanced symptom screening is currently advocated, and the wide application of affordable molecular diagnostics is urgently needed. Treatment of TB/HIV co-infection involves the concurrent use of standard antiretrovirals and antimycobacterials during which harmful drug interaction may occur. The pharmacokinetic interaction between rifamycin and antiretrovirals is a case in point, requiring dosage adjustment and preferential use of rifabutin, if available. Early initiation of antiretroviral therapy is indicated, preferably at 2 weeks after starting TB treatment for patients with a CD4 of <50 cells/μL. Development of TB-immune reconstitution inflammatory syndrome (TB-IRIS) is however more frequent with early antiretroviral therapy. The diagnosis of TB-IRIS is another clinical challenge, and cautious use of corticosteroids is suggested to improve clinical outcome. As a preventive measure against active TB disease, the screening for latent TB infection should be widely practiced, followed by at least 6-9 months of isoniazid treatment. To date tuberculin skin test remains the only diagnostic tool in high TB burden countries. The role of alternative tests, for example, interferon-γ release assay, would need to be better defined for clinical application.

Plasma concentrations, efficacy and safety of efavirenz in HIV-infected adults treated for tuberculosis in Cambodia (ANRS 1295-CIPRA KH001 CAMELIA trial)

OBJECTIVE

To assess efavirenz plasma concentrations and their association with treatment efficacy and tolerance of efavirenz 600 mg daily in HIV-tuberculosis co-infected patients.

METHODS

HIV-infected adults with CD4+ T cell count ≤ 200/mm(3) received standard 6-month tuberculosis treatment and antiretroviral therapy including a daily-dose of 600 mg of efavirenz, irrespective of their body weight. Mid-dose blood samples were drawn both on tuberculosis treatment (week +2 and week +6 after antiretroviral therapy initiation, and week 22 of follow-up) and off tuberculosis treatment (week 50 of follow-up). Considered therapeutic range was 1,000 to 4,000 ng/mL. Multivariate analysis was performed to evaluate the association between efavirenz concentration below 1,000 ng/mL and virological failure. Linear regression was used to test the association between efavirenz exposure and CD4+ T cell gain. Severe side effects potentially related to efavirenz were described and their association with efavirenz exposure was tested by multivariate analysis.

RESULTS

Efavirenz plasma concentrations were available in 540 patients. Median [interquartile range] efavirenz concentrations were 2,674 ng/mL [1,690-4,533], 2,667 ng/mL [1,753-4,494] and 2,799 ng/mL [1,804-4,744] at week +2, week +6, week 22, respectively, and 2,766 ng/mL [1,941-3,976] at week 50. Efavirenz concentrations were lower at week 50 (off rifampicin) compared to week 22 (on rifampicin) (p<0.001). Late attendance to study visit and low hemoglobinemia were the only factors associated with an increased risk of efavirenz concentration below 1,000 ng/mL. Efavirenz concentration below 1,000 ng/mL was not associated with treatment failure. Efavirenz concentration above 4,000 ng/mL was associated with higher risk of central nervous system side effects (p<0.001) and of hepatotoxicity (p<0.001).

CONCLUSION

Body weight and tuberculosis treatment were not associated with low efavirenz concentrations or treatment failure, supporting the 600 mg daily-dose of efavirenz in HIV-tuberculosis co-infected patients. High efavirenz concentrations were related to a higher risk of central nervous system side effects and hepatotoxicity.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01300481.

Changes to antiretroviral drug regimens during integrated TB-HIV treatment: results of the SAPiT trial

BACKGROUND

Frequency of drug changes in combination antiretroviral therapy among patients starting both tuberculosis (TB) and HIV therapy, as a result of treatment-limiting toxicity or virological failure, is not well established.

METHODS

Patients in the Starting Antiretroviral Therapy at Three Points in Tuberculosis (SAPiT) trial were randomized to initiate antiretroviral therapy (ART) either early or late during TB treatment or after completion of TB treatment. Drug changes due to toxicity (defined as due to grade 3 or 4 adverse events) or virological failure (defined as viral load >1,000 copies/ml on two occasions, taken ≥4 weeks apart) were assessed in these patients.

RESULTS

A total of 501 TB-HIV-coinfected patients were followed for a mean of 16.0 months (95% CI 15.5, 16.6) after ART initiation. The standard first-line antiretrovirals used were efavirenz, lamivudine and didanosine. Individual drug switches for toxicity occurred in 14 patients (incidence rate 2.1 per 100 person-years, 95% CI 1.1, 3.5), and complete regimen changes due to virological failure in 25 patients (incidence rate 3.7 per 100 person-years, 95% CI 2.4, 5.5). The most common treatment limiting toxicities were neuropsychiatric effects (n=4, 0.8%), elevated transaminase levels and hyperlactataemia (n=3, 0.6%), and peripheral neuropathy (n=2, 0.4%). Complete regimen change due to treatment failure was more common in patients with CD4(+) T-cell count <50 cells/mm(3) (P<0.001) at ART initiation and body mass index >25 kg/m(2) (P=0.01) at entry into the study.

CONCLUSIONS

Both drug switches and complete regimen change were uncommon in patients cotreated for TB-HIV with the chosen regimen. Patients with severe immunosuppression need to be monitored carefully, as they were most at risk for treatment failure requiring regimen change.

EFV/FTC/TDF-associated hepatotoxicity: a case report and review

The fixed-dose combination efavirenz, emtricitabine, and tenofovir (EFV/FTC/TDF) is a first-line agent for the treatment of HIV. We report the case of a 40-year-old female with a history of HIV acquired through heterosexual contact who initiated EFV/FTC/TDF. Hepatitis B and C serologies were negative, CD4 cell count was 253 cells per cubic millimeter (15.8%), and HIV viral load was 67,373 copies per milliliter. Eight months later she developed transaminitis and severe right upper quadrant pain. Neither illicit drug abuse nor hepatotoxic medication such as acetaminophen was reported. After evaluation including negative acute viral hepatitis studies, EFV/FTC/TDF was discontinued; both her transaminitis and pain resolved. Hepatotoxicity is most often associated with efavirenz. Rarely, fulminant hepatic failure occurs. Efavirenz-related hepatotoxicity is thought to result from a cellular self-digestion process known as autophagy. This is the first report to our knowledge of EFV/FTC/TDF-related hepatotoxicity.

Effects of rifampin-based antituberculosis therapy on plasma efavirenz concentrations in children vary by CYP2B6 genotype

OBJECTIVES

An efavirenz-based antiretroviral therapy (ART) regimen is preferred for children more than 3 years of age with tuberculosis. However, rifampin, a key component of antituberculosis therapy, induces CYP2B6. An increased dose of efavirenz is recommended in adults weighing more than 50 kg who require rifampin, but there is scant information in children being treated for tuberculosis.

DESIGN

Plasma efavirenz concentrations were compared in 40 children during concomitant treatment for tuberculosis and HIV-1, after stopping rifampicin, and in a control group of children without tuberculosis. Associations with antituberculosis treatment, metabolizer genotype (based on CYP2B6 516G→T, 983T→C, and 15582C→T), weight, and time after dose were evaluated.

RESULTS

Compared to children with extensive metabolizer genotypes, efavirenz concentrations were increased 1.42-fold (95% confidence interval, CI 0.94–2.15) and 2.85-fold (95% CI 1.80–4.52) in children with intermediate and slow metabolizer genotypes, respectively. Concomitant antituberculosis treatment increased efavirenz concentrations 1.49-fold (95% CI 1.10–2.01) in children with slow metabolizer genotypes, but did not affect efavirenz concentrations in extensive or intermediate metabolizer genotypes. After adjustment for dose/kg, each kilogram of weight was associated with a 2.8% (95% CI 0.9–4.7) decrease in efavirenz concentrations. Despite higher milligram per kilogram doses, a higher proportion of children in the lowest weight band (10–13.9 kg) had efavirenz concentrations less than 1.0 mg/l than larger children.

CONCLUSION

Antituberculosis treatment was not associated with reduced efavirenz concentrations in children, which does not support increased efavirenz doses. Children with slow metabolizer genotype have increased efavirenz concentrations during antituberculosis treatment, likely due to isoniazid inhibiting enzymes involved in accessory metabolic pathways for efavirenz.

Influence of efavirenz pharmacokinetics and pharmacogenetics on neuropsychological disorders in Ugandan HIV-positive patients with or without tuberculosis: a prospective cohort study

Background

HIV infection, anti-tuberculosis and efavirenz therapy are associated with neuropsychological effects. We evaluated the influence of rifampicin cotreatment, efavirenz pharmacokinetics and pharmacogenetics on neuropsychiatric disorders in Ugandan HIV patients with or without tuberculosis coinfection.

Methods

197 treatment naïve Ugandan HIV patients, of whom 138 were TB co-infected, enrolled prospectively and received efavirenz based HAART. TB-HIV confected patients received concomitant rifampicin based anti-TB therapy. Genotypes for CYP2B6 (*6, *11), CYP3A5 (*3, *6, *7), ABCB1 (c.3435C>T and c.4036 A/G rs3842), CYP2A6 (*9, *17) and NR1I3 rs3003596 T/C were determined. Efavirenz plasma concentrations were serially quantified at 3rd day, 1st, 2nd, 4th, 6th, 8th and 12th weeks during therapy. Efavirenz neuropsychiatric symptoms were evaluated in terms of sleep disorders, hallucinations and cognitive effects at baseline, at two and twelve weeks of efavirenz treatment using a modified Mini Mental State Examination (MMSE) score.

Results

During the first twelve weeks of ART, 73.6% of the patients experienced at least one efavirenz related neuropsychiatric symptom. Commonest symptoms experienced were sleep disorders 60.5% (n=124) and hallucination 30.7% (n=63). Neuropsychiatric symptoms during HAART were significantly predicted by efavirenz plasma concentrations consistently. Rifampicin cotreatment reduced plasma efavirenz concentrations significantly only during the first week but not afterwards. There was no significant difference in the incidence of neuropsychiatric symptoms between patients receiving efavirenz with or without rifampicin cotreatment. CYP2B6*6 and ABCB1 c.4036 A/G genotype significantly predicted efavirenz concentrations. The tendency of CYP2B6*6 genotype association with higher incidence of having vivid dream (p=0.05), insomnia (p=0.19) and tactile hallucination (p=0.09) was observed mainly at week-2.

Conclusions

Efavirenz related neuropsychiatric symptoms are common among Ugandan HIV patients receiving ART and is mainly predicted by higher efavirenz plasma concentrations and CYP2B6 genotype but not by rifampicin based anti-TB co-treatment.

Relationship between weight, efavirenz exposure, and virologic suppression in HIV-infected patients on rifampin-based tuberculosis treatment in the AIDS Clinical Trials Group A5221 STRIDE Study

BACKGROUND

Rifampin (RIF) upregulates CYP 450 isoenzymes, potentially lowering efavirenz (EFV) exposure. The US EFV package insert recommends an EFV dose increase for patients on RIF weighing ≥50 kg. We conducted a pharmacokinetic study to evaluate EFV trough concentrations (Cmin) and human immunodeficiency virus (HIV) virologic suppression in patients on EFV (600 mg) and RIF-based tuberculosis treatment in the multicenter randomized trial (ACTG A5221).

METHODS

EFV Cmin was measured 20-28 hours post-EFV dose at weeks 4, 8, 16, 24 on-RIF and weeks 4, 8 off-RIF. Results were evaluated with 2-sided Wilcoxon rank-sum, χ(2), Fisher exact tests and logistic regression (5% type I error rate).

RESULTS

Seven hundred eighty patients received EFV; 543 provided ≥1 EFV Cmin. Median weight was 52.8 kg (interquartile range [IQR], 48.0-59.5), body mass index 19.4 kg/m(2) (IQR, 17.5-21.6), and age 34 years (IQR, 29-41); 63% were male, 74% black. Median Cmin was 1.96 µg/mL on-RIF versus 1.80 off-RIF (P = .067). Cmin were significantly higher on-RIF versus off-RIF in blacks (2.08 vs 1.75, P = .005). Weight ≥60 kg on-RIF, compared to <60 kg, was associated with lower EFV Cmin (1.68 vs 2.02, P = .021). However, weight ≥60 kg was associated with more frequent HIV RNA < 400 copies/mL at week 48, compared to weight <60 kg (81.9% vs 73.8%, P = .023).

CONCLUSIONS

EFV and RIF-based tuberculosis therapy coadministration was associated with a trend toward higher, not lower, EFV Cmin compared to EFV alone. Patients weighing ≥60 kg had lower median EFV Cmin versus those <60 kg, but there was no association of higher weight with reduced virologic suppression. These data do not support weight-based dosing of EFV with RIF.

Clinical pharmacokinetics of antiretroviral drugs in older persons

INTRODUCTION

Combination antiretroviral therapy has enabled HIV-infected persons to reach older ages in high numbers. Hepatic and renal changes that normally occur with advancing age occur earlier and with higher incidence in HIV-infected individuals. A limited number of prospective controlled studies have demonstrated small reductions (17 to 41%) in lopinavir, atazanavir and lamivudine clearance in older versus younger adults. A much larger number of retrospective studies in adults (age range ∼ 20 to 60 years), including all antiretroviral drugs, have evaluated age as a covariate for pharmacokinetics. Most studies did not detect substantial associations between drug exposures and age.

AREAS COVERED

This review summarizes antiretroviral drug pharmacokinetics in older persons. The authors review articles from PubMed (search terms: elderly, antiretroviral, pharmacokinetics) in addition to the bibliographies of those selected.

EXPERT OPINION

The evidence to date does not support major pharmacokinetic changes in adults between ∼ 20 and 60 years of age. However, additional prospective, well-controlled studies are needed in more persons > 60 years, including those with frailty and comorbidities, with assessment of unbound drug clearance, and incorporation of adherence, pharmacogenetics and concomitant medications. Until then, guidelines for drug-drug interactions and dosing in renal and hepatic impairment should be followed in older HIV-infected individuals.

Nevirapine versus efavirenz for patients co-infected with HIV and tuberculosis: a randomised non-inferiority trial

BACKGROUND

In countries with a high incidence of HIV and tuberculosis co-infection, nevirapine and efavirenz are widely used as antiretroviral therapy but both interact with antituberculosis drugs. We aimed to compare efficacy and safety of a nevirapine-based antiretroviral therapy (started at full dose) with an efavirenz-based regimen in co-infected patients.

METHODS

We did a multicentre, open-label, randomised, non-inferiority trial at three health centres in Maputo, Mozambique. We enrolled adults (≥18 years) with tuberculosis and previously untreated HIV infection (CD4 cell counts <250 cells per μL) and alanine aminotransferase and total bilirubin concentrations of less than five times the upper limit of normal. 4-6 weeks after the start of tuberculosis treatment, we randomly allocated patients (1:1) with central randomisation, block sizes of two to six, and stratified by site and CD4 cell count to nevirapine (200 mg twice daily) or efavirenz (600 mg once daily), plus lamivudine and stavudine. The primary endpoint was virological suppression at 48 weeks (HIV-1 RNA <50 copies per mL) in all patients who received at least one dose of study drug (intention-to-treat population); death and loss to follow-up were recorded as treatment failure. The non-inferiority margin for the difference of efficacy was 10%. We assessed efficacy in intention-to-treat and per-protocol populations and safety in all patients who received study drug. This study is registered with ClinicalTrials.gov, number NCT00495326.

FINDINGS

Between October, 2007, and March, 2010, we enrolled 285 patients into each group. 242 (85%) patients in the nevirapine group and 233 (82%) patients in the efavirenz group completed follow-up. In the intention-to-treat population, 184 patients (64·6%, 95% CI 58·7-70·1) allocated nevirapine achieved virological suppression at week 48, as did 199 patients (69·8%, 64·1-75·1) allocated efavirenz (one-sided 95% CI of the difference of efficacy 11·7%). In the per-protocol population, 170 (70·0%, 63·8-75·7) of 243 patients allocated nevirapine achieved virological suppression at week 48, as did 194 (78·9%, 73·2-83·8) of 246 patients allocated efavirenz (one-sided 95% CI 15·4%). The median CD4 cell count at randomisation was 89 cells per μL. 15 patients substituted nevirapine with efavirenz and six patients substituted efavirenz with nevirapine. 20 patients allocated nevirapine (7%) had grade 3-4 increase of alanine aminotransferase compared with 17 patients allocated efavirenz (6%). Three patients had severe rash after receipt of nevirapine (1%) but no patients did after receipt of efavirenz. 18 patients in the nevirapine group died, as did 17 patients in the efavirenz group.

INTERPRETATION

Although non-inferiority of the nevirapine-regimen was not shown, nevirapine at full dose could be a safe, acceptable alternative for patients unable to tolerate efavirenz.

FUNDING

French Research Agency for HIV/AIDS and hepatitis (ANRS).

When to start antiretroviral therapy during tuberculosis treatment?

PURPOSE OF REVIEW

Effective treatment exists for tuberculosis (TB) and for HIV, but treating both diseases simultaneously presents several challenges. This review assesses the evidence for the timing of antiretroviral therapy (ART) initiation in patients coinfected with TB.

RECENT FINDINGS

Published evidence clearly demonstrates that TB-HIV integration is essential for improved survival, but the question of when to start ART during TB treatment is more complex. Five randomized controlled trials assessed this question: four trials showed no difference in the incidence rates of AIDS or death between TB patients initiating ART within 2 months compared to later during TB therapy, while one trial showed a significant survival gain with ART initiation within 2 weeks of TB therapy start. All five studies found improved AIDS-free survival with earlier ART initiation in TB patients with low CD4 T-cell counts, except among patients with TB meningitis. The survival benefit was, however, accompanied by increased immune reconstitution inflammatory syndrome events.

SUMMARY

The trial data support the World Health Organization recommendations on when to start ART in TB-HIV coinfected patients including earlier ART initiation in severely immune-compromised patients. However, several challenges remain in integrating TB and HIV treatment in public healthcare services. Additional research on timing of ART is needed for patients with drug-resistant and extrapulmonary TB, notably TB meningitis.

Plasma concentrations of efavirenz with a 600 mg standard dose in Cambodian HIV-infected adults treated for tuberculosis with a body weight above 50 kg

BACKGROUND

The optimal dose of efavirenz for HIV-infected patients receiving a tuberculosis regimen including rifampicin remains debated, especially for subjects weighing over 50 kg. To address this issue, we measured plasma efavirenz concentrations from Cambodian adults with tuberculosis enrolled in the CAMELIA randomized trial (ClinicalTrials.gov number, NCT01300481) 6 weeks after the onset of antiretroviral therapy.

METHODS

Efavirenz concentrations and proportions of patients with concentrations below 1,000 ng/ml were compared across patient body weight below or above 50 kg using a Student's t-test and a χ(2) test, respectively. Factors associated with efavirenz concentrations below 1,000 ng/ml were identified by logistic regression analysis. Logistic regression analysis was also performed to check if efavirenz concentrations below 1,000 ng/ml were associated with virological failure.

RESULTS

Plasma efavirenz concentrations were higher in the 332 patients who weighed <50 kg compared with the 150 who weighed ≥50 kg (median [IQR] 2,859 [1,787-4,749] and 2,060 [1,425-3,575] ng/ml, respectively; P=0.02). However, the proportion of patients with efavirenz concentrations below 1,000 ng/ml was not different between those weighing less than or more than 50 kg (6% and 10%, respectively; P=0.13) and a body weight above 50 kg was not associated with a higher risk of plasma efavirenz concentrations below 1,000 ng/ml. When plasma efavirenz concentrations below 1,000 ng/ml were present, they were not associated with virological failure.

CONCLUSIONS

The current WHO guidelines recommending 600 mg efavirenz daily irrespective of patient's body weight remains a safe and effective approach to treating coinfected adults needing simultaneous tuberculosis and HIV therapy.