Efavirenz and rifampicin in the South African context: is there a need to dose-increase efavirenz with concurrent rifampicin therapy?

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.

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.

Isolation and Molecular Identification of Virulence, Antimicrobial and Heavy Metal Resistance Genes in Livestock-Associated Methicillin-Resistant Staphylococcus aureus

Staphylococcus aureus is one of the most important pathogens of humans and animals. Livestock production contributes a significant proportion to the South African Gross Domestic Product. Consequently, the aim of this study was to determine for the first time the prevalence, virulence, antibiotic and heavy metal resistance in livestock-associated S. aureus isolated from South African livestock production systems. Microbial phenotypic methods were used to detect the presence of antibiotic and heavy metal resistance. Furthermore, molecular DNA based methods were used to genetically determine virulence as well as antibiotic and heavy metal resistance determinants. Polymerase chain reaction (PCR) confirmed 217 out of 403 (53.8%) isolates to be S. aureus. Kirby-Bauer disc diffusion method was conducted to evaluate antibiotic resistance and 90.8% of S. aureus isolates were found to be resistant to at least three antibiotics, and therefore, classified as multidrug resistant. Of the antibiotics tested, 98% of the isolates demonstrated resistance towards penicillin G. High resistance was shown against different heavy metals, with 90% (196/217), 88% (192/217), 86% (188/217) and 84% (183/217) of the isolates resistant to 1500 µg/mL concentration of Cadmium (Cd), Zinc (Zn), Lead (Pb) and Copper (Cu) respectively. A total of 10 antimicrobial resistance and virulence genetic determinants were screened for all livestock associated S. aureus isolates. Methicillin-resistant S. aureus (MRSA) isolates were identified, by the presence of mecC, in 27% of the isolates with a significant relationship (p < 0.001)) with the host animal. This is the first report of mecC positive LA-MRSA in South Africa and the African continent. The gene for tetracycline resistance (tetK) was the most frequently detected of the screened genes with an overall prevalence of 35% and the highest prevalence percentage was observed for goats (56.76%) followed by avian species (chicken, duck and wild birds) (42.5%). Virulence-associated genes were observed across all animal host species. The study reports the presence of luks/pv, a gene encoding the PVL toxin previously described to be a marker for community acquired-MRSA, suggesting the crossing of species between human and livestock. The high prevalence of S. aureus from the livestock indicates a major food security and healthcare threat. This threat is further compounded by the virulence of the pathogen, which causes numerous clinical manifestations. The phenomenon of co-selection is observed in this study as isolates exhibited resistance to both antibiotics and heavy metals. Further, all the screened antibiotic and heavy metal resistance genes did not correspond with the phenotypic resistance.

Effect of Rifampin-Isoniazid-Containing Antituberculosis Therapy on Efavirenz Pharmacokinetics in HIV-Infected Children 3 to 14 Years Old

We compared efavirenz pharmacokinetic (PK) parameters in children with tuberculosis (TB)/human immunodeficiency virus (HIV) coinfection on and off first-line antituberculosis therapy to that in HIV-infected children. Children 3 to 14 years old with HIV infection, with and without TB, were treated with standard efavirenz-based antiretroviral therapy without any efavirenz dose adjustments. The new World Health Organization-recommended antituberculosis drug dosages were used in the coinfected participants. Steady-state efavirenz concentrations after 4 weeks of antiretroviral therapy were measured using validated liquid chromatography with tandem mass spectrometry (LC-MS/MS) assays. Pharmacokinetic parameters were calculated using noncompartmental analysis. Between groups, PK parameters were compared by Wilcoxon rank-sum test and within group by signed-rank test. Of the 105 participants, 43 (41.0%) had TB coinfection. Children with TB/HIV coinfection compared to those with HIV infection were younger, had lower median weight-for-age Z score, and received a higher median efavirenz weight-adjusted dose. Geometric mean (GM) efavirenz peak concentration (Cmax), concentration at 12 h (C12h), Cmin, and total area under the curve from time 0 to 24 h (AUC0-24h) values were similar in children with HIV infection and those with TB/HIV coinfection during anti-TB therapy. Geometric mean efavirenz C12h, Cmin, and AUC0-24h values were lower in TB/HIV-coinfected patients off anti-TB therapy than in the children with HIV infection or TB/HIV coinfection on anti-TB therapy. Efavirenz clearance was lower and AUC0-24h was higher on than in patients off anti-TB therapy. Reduced efavirenz clearance by first-line anti-TB therapy at the population level led to similar PK parameters in HIV-infected children with and without TB coinfection. Our findings do not support modification of efavirenz weight-band dosing guidelines based on TB coinfection status in children. (The study was registered with ClinicalTrials.gov under registration number NCT01704144.).

Daily 800 mg versus 600 mg Efavirenz for HIV Patients Treating Tuberculosis with a Rifampicin-Based Regimen: An Open Label Randomized Controlled Trial

Objectives

Pharmacokinetics studies recommend increasing efavirenz dosage in tuberculosis/HIV patients using rifampicin. We aimed to evaluate efficacy and safety of 600 versus 800 mg of efavirenz in tuberculosis/HIV patients using rifampicin.

Design

We conducted an open label, multicentre, randomized trial from 2006 to 2012. The primary outcome was the proportion of undetectable viral load (HIV-VL) within six months. Secondary outcomes were time to achieve primary endpoint, trajectories of HIV-VL, proportion of any adverse events (AE), proportion of severe and serious AE (SSAE), and time to treatment interruption due to SSAE.

Methods

Efavirenz-naïve patients were randomized 30 days after rifampicin-containing regimens initiation to receive 600 (comparison arm) or 800 mg (intervention arm) efavirenz-based regimens and followed-up for 180 days.

Results

Sixty-five and 67 participants were respectively included in the comparison and intervention arms with 64.6% (52.5%-65.1%) and 62.7% (50.7%-73.3%) attaining undetectable HIV-VL in six months. Median time to attain undetectable HIV-VL was 70 days in both arms, with HIV-VL overlapping trajectories during follow-up. Cough, acne, and dizziness were more frequent in the intervention arm. SSAE were observed in 19.1% (13.8%-25.8%) and 25.0% (18.9%-33.2%), respectively. Survival curves up to the first SSAE-attributed treatment interruption were similar. None of the differences were statistically significant.

Conclusion

Efficacy of efavirenz was similar regardless of dosage. Differences regarding safety occurred as mild and transient events, which did not interfere with treatment. Similar efficacy and safety (SSAE) and lower tolerance (minor AE) in the intervention group favour the use of 600 mg efavirenz in patients using rifampicin.

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.

Pharmacogenomics and Global Precision Medicine in the Context of Adverse Drug Reactions: Top 10 Opportunities and Challenges for the Next Decade

In a move indicative of the enthusiastic support of precision medicine, the U.S. President Barack Obama announced the Precision Medicine Initiative in January 2015. The global precision medicine ecosystem is, thus, receiving generous support from the United States ($215 million), and numerous other governments have followed suit. In the context of precision medicine, drug treatment and prediction of its outcomes have been important for nearly six decades in the field of pharmacogenomics. The field offers an elegant solution for minimizing the effects and occurrence of adverse drug reactions (ADRs). The Clinical Pharmacogenetics Implementation Consortium (CPIC) plays an important role in this context, and it aims at specifically guiding the translation of clinically relevant and evidence-based pharmacogenomics research. In this forward-looking analysis, we make particular reference to several of the CPIC guidelines and their role in guiding the treatment of highly relevant diseases, namely cardiovascular disease, major depressive disorder, cancer, and human immunodeficiency virus, with a view to predicting and managing ADRs. In addition, we provide a list of the top 10 crosscutting opportunities and challenges facing the fields of precision medicine and pharmacogenomics, which have broad applicability independent of the drug class involved. Many of these opportunities and challenges pertain to infrastructure, study design, policy, and science culture in the early 21st century. Ultimately, rational pharmacogenomics study design and the acquisition of comprehensive phenotypic data that proportionately match the genomics data should be an imperative as we move forward toward global precision medicine.

Long-Term Effect of Rifampicin-Based Anti-TB Regimen Coadministration on the Pharmacokinetic Parameters of Efavirenz and 8-Hydroxy-Efavirenz in Ethiopian Patients

We compared the pharmacokinetic (PK) exposure parameters of efavirenz (EFV) and its major inactive metabolite, 8-hydroxy-efavirenz (8-OH-EFV), in an open-label, single-sequence, and parallel design of HIV-infected and tuberculosis (TB)-HIV-coinfected Ethiopian patients in the HIV-TB Pharmagene study with 20 and 33 patients, respectively. Both treatment groups underwent PK sampling following oral 600 mg EFV in week 16 of initiating EFV-based combination antiretroviral therapy. The TB-HIV-coinfected group repeated the PK sampling 8 weeks after stopping rifampin (RIF)-based anti-TB treatment. Between-treatment group analysis indicated no significant effect of RIF-based anti-TB cotreatment on PK exposure parameters of EFV, nor was there a significant effect after controlling for sex or CYP2B6 genotype. However, RIF-based therapy in TB-HIV-coinfected patients had significantly increased 8-OH-EFV PK exposure measures and metabolic ratio relative to HIV-only patients, AUC_0-24 greater by 79%. The effect was more prominent in women and CYP2B6*6 carriers in within-sex and CYP2B6 genotype comparisons. Within-subject comparisons for AUC_0-24 and C_max when "on" and "off" RIF-based anti-TB cotreatment showed geometric mean ratios (90% confidence intervals) of 100.5% (98.7%-102.3%) and 100.2% (98.1%-102.4%), respectively, for EFV and 98.6% (95.5%-101.7%-) and 97.6% (92.2%-103.0%), respectively, for 8-OH-EFV. We report no significant influence of RIF-based anti-TB cotherapy on the EFV PK exposure measures. The study also calls for caution related to higher exposure to 8-OH-EFV during simultaneous coadministration of EFV and RIF-based anti-TB regimens, which may be associated with neurotoxicity, particularly in female patients and CYP2B6*6 carriers.

Tenofovir DF/emtricitabine and efavirenz combination therapy for HIV infection in patients treated for tuberculosis: the ANRS 129 BKVIR trial

BACKGROUND

HIV-infected patients with TB need simplified, effective and well-tolerated antiretroviral regimens.

METHODS

The French ANRS 129 BKVIR open trial evaluated the once-daily tenofovir DF/emtricitabine and efavirenz combination, started within 12 weeks after TB treatment initiation, in antiretroviral-naive HIV-1-infected patients. Success was defined as an HIV-1 RNA <50 copies/mL and TB cure at 48 weeks.

RESULTS

TB was confirmed microbiologically (90%) or histologically (10%) in 69 patients (71% male; median age 43 years; 54% born in Africa). The median time between TB treatment initiation and antiretroviral therapy was 8 weeks (range 1-22 weeks). At baseline, median HIV-1 RNA was 5.4 log10 copies/mL and median CD4 cell count 74 cells/mm(3). In the ITT analysis, combined success at week 48 was achieved in 57/69 patients (83%, 95% CI 74-92). Twelve patients did not achieve virological success, and TB was not cured in one of them. Among the 47 patients who fully adhered to the strategy, the success rate was 96% (95% CI 90-100) and was not affected by low rifampicin and isoniazid serum concentrations. Forty-nine serious adverse events were reported in 31 patients (45%), and 11 led to antiretroviral drug interruption. All adverse events resolved. The immune reconstitution inflammatory syndrome occurred in 23 patients (33%, 95% CI 22-44), and was associated with a low baseline BMI (P = 0.03) and a low haemoglobin level (P = 0.02).

CONCLUSION

These results support the use of tenofovir DF/emtricitabine and efavirenz combination therapy for HIV infection in 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.

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.

The Use of Therapeutic Drug Monitoring in Complex Antituberculous and Antiretroviral Drug Dosing in HIV/Tuberculosis-Coinfected Patients

We report 2 cases coinfected with HIV and tuberculosis (HIV/TB), requiring drug dose adjustments guided by therapeutic drug monitoring (TDM) and/or serum drug concentrations.

CASE 1

Over the course of the 9-months of TB treatment, drugs that required increased doses due to low concentrations included efavirenz (800 mg), rifampin (900 mg), and isoniazid (450 mg). Higher drug doses were well tolerated until the end of treatment.

CASE 2

Over the 12-month course of TB therapy, drugs that required increased doses due to incomplete and/or delayed absorption were rifampin (1500 mg), moxifloxacin (800 mg), and ethambutol (1600 mg). Higher drug doses were well tolerated until the end of treatment. Due to delayed/incomplete drug absorption and weight gain during therapy, higher antituberculous doses may be required in patients coinfected with HIV/TB. A daily dose of efavirenz 800 mg was well tolerated in both patients (weight over 70 kg). Managing patients coinfected with HIV/TB is complex, and, therefore, TDM of drug concentrations can help guide clinical decision making.

Efficacy of 400 mg efavirenz versus standard 600 mg dose in HIV-infected, antiretroviral-naive adults (ENCORE1): a randomised, double-blind, placebo-controlled, non-inferiority trial

BACKGROUND

The optimum dose of key antiretroviral drugs is often overlooked during product development. The ENCORE1 study compared the efficacy and safety of reduced dose efavirenz with standard dose efavirenz in combination with tenofovir and emtricitabine as first-line treatment for HIV infection. An effective and safe reduced dose could yield meaningful cost savings.

METHODS

ENCORE1 is a continuing non-inferiority trial in HIV-1-infected antiretroviral-naive adults in 38 clinical sites in 13 countries. Participants (plasma HIV-RNA >1000 log10 copies per mL, CD4 T-cell count 50-500 cells per μL) were randomly assigned by a computer-generated sequence with a blocking factor of four (stratified by clinical site and by screening viral load) to receive tenofovir plus emtricitabine with either a reduced daily dose (400 mg) or a standard dose (600 mg) of efavirenz. Participants, physicians, and all other trial staff were masked to treatment group. The primary endpoint was the difference in proportions of participants with plasma HIV-RNA of less than 200 copies per mL at 48 weeks. Treatment groups were regarded as non-inferior if the lower limit of the 95% CI for the difference in viral load was less than -10% by modified intention-to-treat analysis. Adverse events were summarised by treatment. This trial is registered with ClinicalTrials.gov, number NCT01011413.

FINDINGS

The modified intention-to-treat analysis consisted of 630 patients (efavirenz 400=321; efavirenz 600=309). 32% were women; 37% were African, 33% were Asian, and 30% were white. The mean baseline CD4 cell count was 273 cells per μL (SD 99) and median plasma HIV-RNA was 4·75 log10 copies per mL (IQR 0·88). The proportion of participants with a viral load below 200 copies per mL at week 48 was 94·1% for efavirenz 400 mg and 92·2% for 600 mg (difference 1·85%, 95% CI -2·1 to 5·79). CD4 T-cell counts at week 48 were significantly higher for the 400 mg group than for the 600 mg group (mean difference 25 cells per μL, 95% CI 6-44; p=0·01). We recorded no difference in grade or number of patients reporting adverse events (efavirenz 400=89·1%, efavirenz 600=88·4%; difference 0·75%, 95% CI -4·19 to 5·69; p=0·77). Study drug-related adverse events were significantly more frequent in the 600 mg group than in the 400 mg group (146% [47] vs 118 [37]), difference -10·5%, 95% CI -18·2 to -2·8; p=0·01) and significantly fewer patients with these events stopped treatment (400 mg=6 [2%], 600 mg=18 [6%], difference -3·96%, 95% CI -6·96 to -0·95; p=0·01).

INTERPRETATION

Our findings suggest that a reduced dose of 400 mg efavirenz is non-inferior to the standard dose of 600 mg, when combined with tenofovir and emtricitabine during 48 weeks in ART-naive adults with HIV-1 infection. Adverse events related to the study drug were more frequent with 600 mg efavirenz than with 400 mg. Lower dose efavirenz should be recommended as part of routine care.

FUNDING

Bill & Melinda Gates Foundation, University of New South Wales.

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.

Viral suppression following switch to second-line antiretroviral therapy: associations with nucleoside reverse transcriptase inhibitor resistance and subtherapeutic drug concentrations prior to switch

BACKGROUND

High rates of second-line antiretroviral treatment (ART) failure are reported. The association with resistance and nonadherence on switching to second-line ART requires clarification.

METHODS

Using prospectively collected data from patients in South Africa, we constructed a cohort of patients switched to second-line ART (1 January 2003 through 31 December 2008). Genotyping and drug concentrations (lamivudine, nevirapine, and efavirenz) were measured on stored samples preswitch. Their association with viral load (VL) <400 copies/mL by 15 months was assessed using modified Poisson regression.

RESULTS

One hundred twenty-two of 417 patients (49% male; median age, 36 years) had genotyping (n = 115) and/or drug concentrations (n = 80) measured. Median CD4 count and VL at switch were 177 cells/µL (interquartile range [IQR], 77-263) and 4.3 log10 copies/mL (IQR, 3.8-4.7), respectively. Fifty-five percent (n = 44/80) had subtherapeutic drug concentrations preswitch. More patients with therapeutic vs subtherapeutic ART had resistance (n = 73): no major mutations (3% vs 51%), nonnucleoside reverse transcriptase inhibitor (94% vs 44%), M184V/I (94% vs 26%), and ≥ 1 thymidine analogue mutations (47% vs 18%), all P = .01; and nucleoside reverse transcriptase inhibitor (NRTI) cross-resistance mutations (26% vs 13%, P = .23). Following switch, 68% (n = 83/122) achieved VL <400 copies/mL. Absence of NRTI mutations and subtherapeutic ART preswitch were associated with failure to achieve VL <400 copies/mL.

CONCLUSIONS

Nonadherence, suggested by subtherapeutic ART with/without major resistance mutations, significantly contributed to failure when switching regimen. Unresolved nonadherence, not NRTI resistance, drives early second-line failure.

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.

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.

Efavirenz, tenofovir and emtricitabine combined with first-line tuberculosis treatment in tuberculosis-HIV-coinfected Tanzanian patients: a pharmacokinetic and safety study

BACKGROUND

To evaluate the effect of rifampicin-based tuberculosis (TB) treatment on the pharmacokinetics of efavirenz/tenofovir/emtricitabine in a fixed-dose combination tablet, and vice versa, in Tanzanian TB-HIV-coinfected patients.

METHODS

This was a Phase II open-label multiple dose pharmacokinetic and safety study. This study was conducted in TB-HIV-coinfected Tanzanian patients who started TB treatment (rifampicin/isoniazid/pyrazinamide/ethambutol) at week 1 to week 8 and continued with rifampicin and isoniazid for another 16 weeks. Antiretroviral treatment (ART) of efavirenz/tenofovir/emtricitabine in a fixed-dose combination tablet was started at week 4 after initiation of TB treatment. A 24-h pharmacokinetic sampling curve was recorded at week 8 (with TB treatment) and week 28 (ART alone). For TB drugs, blood samples at 2 and 5 h post-dose were taken at week 3 (TB treatment alone) and week 8 (with ART).

RESULTS

A total of 25 patients (56% male) completed the study; 21 had evaluable pharmacokinetic profiles. The area under the concentration-time curve 0-24 h post-dose of efavirenz, tenofovir and emtricitabine were slightly higher when these drugs were coadministered with TB drugs; geometric mean ratios (90% CI) were 1.08 (0.90, 1.30), 1.13 (0.93, 1.38) and 1.05 (0.85, 1.29), respectively. For TB drugs, equivalence was suggested for peak plasma concentrations when administered with and without efavirenz/tenofovir/emtricitabine. Adverse events were mostly mild and no serious adverse events or drug discontinuations were reported.

CONCLUSIONS

Coadministration of efavirenz, tenofovir and emtricitabine with a standard first-line TB treatment regimen did not significantly alter the pharmacokinetic parameters of these drugs and was tolerated well by Tanzanian TB patients who are coinfected with HIV.

AtriplaR/anti-TB combination in TB/HIV patients. Drug in focus

Background

Co-administration of anti-tuberculosis and antiretroviral therapy is often inevitable in high-burden countries where tuberculosis is the most common opportunistic infection associated with HIV/AIDS. Concurrent use of rifampicin and several antiretroviral drugs is complicated by pharmacokinetic drug-drug interaction.

Method

Pubmed and Google search following the key words tuberculosis, HIV, emtricitabine, tenofovir efavirenz, interaction were used to find relevant information on each drug of the fixed dose combination Atripla^R

Results

Information on generic name, trade name, pharmacokinetic parameter, metabolism and the pharmacokinetic interaction with Anti-TB drugs of emtricitabine, tenofovir, and efavirenz was obtained.

Conclusion

Fixed dose combination of emtricitabine/tenofovir/efavirenz (ATRIPLA^R) which has been approved by Food and Drug Administration shows promising results as far as safety and efficacy is concerned in TB/HIV co-infection patients, hence can be considered effective and safe antiretroviral drug in TB/HIV management for adult and children above 3 years of age.