Modest but variable effect of rifampin on steady-state plasma pharmacokinetics of efavirenz in healthy African-American and Caucasian volunteers

Transfer of antiretroviral drugs into breastmilk: a prospective study from the Swiss Mother and Child HIV Cohort Study

INTRODUCTION

In 2018, Switzerland changed its guidelines to support women living with HIV wishing to breastfeed. The exposure of antiretroviral drugs (ARVs) in breastmilk and the ingested daily dose by the breastfed infant are understudied, notably for newer ARVs. This study aimed to quantify ARV concentrations in maternal plasma and breastmilk to determine the milk/plasma ratio, to estimate daily infant ARV dose from breastfeeding and to measure ARV concentrations in infants.

METHODS

All women wishing to breastfeed were included, regardless of their ARV treatment. Breastmilk and maternal plasma samples were mostly collected at mid-dosing interval.

RESULTS

Twenty-one mother/child pairs were enrolled; of those several were on newer ARVs including 10 raltegravir, 1 bictegravir, 2 rilpivirine, 2 darunavir/ritonavir and 3 tenofovir alafenamide. No vertical HIV transmission was detected (one infant still breastfed). The median milk/plasma ratios were 0.96/0.39 for raltegravir once/twice daily, 0.01 for bictegravir, 1.08 for rilpivirine, 0.12 for darunavir/ritonavir and 4.09 for tenofovir alafenamide. The median estimated infant daily dose (mg/kg) from breastfeeding was 0.02/0.25 for raltegravir once/twice daily, 0.01 for bictegravir, 0.02 for rilpivirine, 0.05 for darunavir/ritonavir and 0.007 for tenofovir alafenamide, resulting in relative infant dose <10% exposure index for all ARVs.

CONCLUSIONS

ARVs were transferred to a variable extent in breastmilk. Nevertheless, the estimated daily ARV dose from breastfeeding remained low. Differential ARV exposure was observed in breastfed infants with some ARVs being below/above their effective concentrations raising the concern of resistance development if HIV infection occurs. More data on this potential risk are warranted to better support breastfeeding.

Pharmacogenetics of interaction between depot medroxyprogesterone acetate and efavirenz, rifampicin, and isoniazid during treatment of HIV and tuberculosis

OBJECTIVE

In AIDS Clinical Trials Group study A5338, concomitant rifampicin, isoniazid, and efavirenz was associated with more rapid plasma medroxyprogesterone acetate (MPA) clearance compared to historical controls without tuberculosis or HIV therapy. We characterized the pharmacogenetics of this interaction.

METHODS

In A5338, women receiving efavirenz-based HIV therapy and rifampicin plus isoniazid for tuberculosis underwent pharmacokinetic evaluations over 12 weeks following a 150-mg intramuscular injection of depot MPA. Data were interpreted with nonlinear mixed-effects modelling. Associations between individual pharmacokinetic parameters and polymorphisms relevant to rifampicin, isoniazid, efavirenz, and MPA were assessed.

RESULTS

Of 62 A5338 participants in four African countries, 44 were evaluable for pharmacokinetic associations, with 17 CYP2B6 normal, 21 intermediate, and 6 poor metabolizers, and 5 NAT2 rapid, 20 intermediate, and 19 slow acetylators. There were no associations between either CYP2B6 or NAT2 genotype and MPA Cmin at week 12, apparent clearance, Cmax, area under the concentration-time curve (AUC) or half-life, or unexplained interindividual variability in clearance, and uptake rate constant or mean transit time of the slow-release fraction (P > 0.05 for each). In exploratory analyses, none of 28 polymorphisms in 14 genes were consistently associated with MPA pharmacokinetic parameters, and none withstood correction for multiple testing.

CONCLUSIONS

Study A5338 suggested that more frequent depot MPA dosing may be appropriate for women receiving rifampicin, isoniazid, and efavirenz. The present results suggest that knowledge of CYP2B6 metabolizer or NAT2 acetylator status does not inform individualized DMPA dosing in this setting.

Pharmacogenetic interactions of rifapentine plus isoniazid with efavirenz or nevirapine

OBJECTIVES

The effect of rifapentine plus isoniazid on efavirenz pharmacokinetics was characterized in AIDS Clinical Trials Group protocol A5279 (NCT01404312). The present analyses characterize pharmacogenetic interactions between these drugs, and with nevirapine.

METHODS

A subset of HIV-positive individuals receiving efavirenz- or nevirapine-containing antiretroviral therapy in A5279 underwent pharmacokinetic evaluations at baseline, and again weeks 2 and 4 after initiating daily rifapentine plus isoniazid. Associations with polymorphisms relevant to efavirenz, nevirapine, isoniazid, and rifapentine pharmacokinetics were assessed.

RESULTS

Of 128 participants, 101 were evaluable for associations with rifapentine and its active 25-desacetyl metabolite, 87 with efavirenz, and 38 with nevirapine. In multivariable analyses, NAT2 slow acetylators had greater week 4 plasma concentrations of rifapentine (P = 2.6 × 10) and 25-desacetyl rifapentine (P = 7.0 × 10) among all participants, and in efavirenz and nevirapine subgroups. NAT2 slow acetylators also had greater plasma efavirenz and nevirapine concentration increases from baseline to week 4, and greater decreases from baseline in clearance. CYP2B6 poor metabolizers had greater efavirenz concentrations at all weeks and greater nevirapine concentrations at baseline. None of 47 additional polymorphisms in 11 genes were significantly associated with pharmacokinetics.

CONCLUSIONS

Among HIV-positive individuals receiving efavirenz or nevirapine, and who then initiated rifapentine plus isoniazid in A5279, NAT2 slow acetylators had greater rifapentine and 25-desacetyl rifapentine concentrations, and greater increases from baseline in plasma efavirenz and nevirapine concentrations. These associations are likely mediated by greater isoniazid exposure in NAT2 slow acetylators.

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.

Evaluation of CYP2B6 Induction and Prediction of Clinical Drug-Drug Interactions: Considerations from the IQ Consortium Induction Working Group-An Industry Perspective

Drug-drug interactions (DDIs) due to CYP2B6 induction have recently gained prominence and clinical induction risk assessment is recommended by regulatory agencies. This work aimed to evaluate the potency of CYP2B6 versus CYP3A4 induction in vitro and from clinical studies and to assess the predictability of efavirenz versus bupropion as clinical probe substrates of CYP2B6 induction. The analysis indicates that the magnitude of CYP3A4 induction was higher than CYP2B6 both in vitro and in vivo. The magnitude of DDIs caused by induction could not be predicted for bupropion with static or dynamic models. On the other hand, the relative induction score, net effect, and physiologically based pharmacokinetics SimCYP models using efavirenz resulted in improved DDI predictions. Although bupropion and efavirenz have been used and are recommended by regulatory agencies as clinical CYP2B6 probe substrates for DDI studies, CYP3A4 contributes to the metabolism of both probes and is induced by all reference CYP2B6 inducers. Therefore, caution must be taken when interpreting clinical induction results because of the lack of selectivity of these probes. Although in vitro-in vivo extrapolation for efavirenz performed better than bupropion, interpretation of the clinical change in exposure is confounded by the coinduction of CYP2B6 and CYP3A4, as well as the increased contribution of CYP3A4 to efavirenz metabolism under induced conditions. Current methods and probe substrates preclude accurate prediction of CYP2B6 induction. Identification of a sensitive and selective clinical substrate for CYP2B6 (fraction metabolized > 0.9) is needed to improve in vitro-in vivo extrapolation for characterizing the potential for CYP2B6-mediated DDIs. Alternative strategies and a framework for evaluating the CYP2B6 induction risk are proposed.

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.

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.

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.

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.

Mycobacterium haemophilum bone and joint infection in HIV/AIDS: case report and literature review

We report a case of disseminated Mycobacterium haemophilum osteomyelitis in a patient with advanced HIV infection, who later developed recurrent immune reconstitution inflammatory syndrome after commencement of antiretroviral therapy. We review previous reports of M. haemophilum bone and joint infection associated with HIV infection and describe the management of M. haemophilum-associated immune reconstitution inflammatory syndrome, including the role of surgery as an adjunctive treatment modality and the potential drug interactions between antiretroviral and antimycobacterial agents.

Novel on-line column extraction apparatus coupled with binary peak focusing for high-performance liquid chromatography determination of rifampicin in human plasma: a strategy for therapeutic drug monitoring

In order to develop a method that is completely suitable for the routine therapeutic drug monitoring, a sensitive and fully automated on-line column extraction apparatus in combination with high-performance liquid chromatography allowing binary peak focusing was developed and validated for the determination of rifampicin in human plasma. Rifapentine was used as an internal standard. The analytical cycle started with the injection of 100 μL of the sample pretreated by protein precipitation in a Venusil SCX extraction column. After the elution, the analytes were transferred and concentrated in an Xtimate C18 trap column. Finally, the trapped analytes were separated by an Xtimate C18 analytical column and were analyzed by an ultraviolet detector at 336 nm. With this new strategy, continuous on-line analysis of the compounds was successfully performed. The method showed excellent performance for the analysis of rifampicin in plasma samples, including calibration curve linearity (All r were larger than 0.9996), sensitivity (lowest limit of quantification was 0.12 μg/mL), method accuracy (within 6.6% in terms of relative error), and precision (relative standard deviations of intra- and interday precision were less than 7.8%). These results demonstrated that the simple, reliable, and automatic method based on on-line column extraction and binary peak focusing is a promising approach for therapeutic drug monitoring in complex biomatrix samples.

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.

Factors associated with variability in rifampin plasma pharmacokinetics and the relationship between rifampin concentrations and induction of efavirenz clearance

STUDY OBJECTIVES

To identify factors associated with variability in rifampin plasma pharmacokinetics and explore the relationship between rifampin pharmacokinetics and change in efavirenz plasma pharmacokinetics with rifampin coadministration.

METHODS

In this randomized, cross-over study, 12 healthy volunteers received either efavirenz 600 mg/day or efavirenz 600 mg with rifampin 600 mg/day for 8 days. After a washout period of at least 2 weeks, subjects crossed over to the alternate 8-day regimen. Samples were obtained for pharmacokinetic assessment on day 8 of each study cycle. Drugs concentrations were determined by a validated high-performance liquid chromatography. Pharmacokinetic parameters were calculated using noncompartmental analysis. Multivariate analysis was used to examine factors associated with rifampin pharmacokinetics. Spearman correlation analysis was used to investigate relationship between rifampin pharmacokinetics and change in efavirenz plasma pharmacokinetics with rifampin coadministration.

MEASUREMENTS AND MAIN RESULTS

Of 11 evaluable subjects, the median interquartile range, rifampin peak concentration (Cmax) , area under the concentration-time curve (AUC0-24 hour ), and weight-normalized clearance were 8.9 (7.3-13.8) μg/ml, 48.8 (29.6-67.4) μg·h/ml, and 0.19 (0.11-0.29) L/h/kg, respectively. Solute carrier organic anion transporter family member 1B1 (SLCO1B1) c.388A→G and SLCO1B1 c.463C→A polymorphisms jointly had significant effect on rifampin Cmax (R(2)  = 0.75). Male sex and SLCO1B1 c.463C→A polymorphism together influenced rifampin AUC0-24 hour (R(2)  = 0.52) and weight-normalized clearance (R(2)  = 0.65). All four volunteers with rifampin Cmax less than 8 μg/ml (lower end of the normal range) had c.463CA genotype. Rifampin Cmax and AUC0-24 hour had no significant relationship with the efavirenz AUC0-24 hour ratio or weight-normalized clearance ratio in the presence versus absence of rifampin (p>0.05).

CONCLUSIONS

Men with the SLCO1B1c.463CA genotype are at increased risk of lower rifampin plasma exposure. However, plasma rifampin concentrations did not correlate with the extent of induction of efavirenz clearance by rifampin during coadministration.

Impact of CYP polymorphisms, ethnicity and sex differences in metabolism on dosing strategies: the case of efavirenz

PURPOSE

Differences in drug metabolism due to cytochrome P450 (CYP) polymorphisms may be significant enough to warrant different dosing strategies in carriers of specific cytochrome P450 (CYP) polymorphisms, especially for drugs with a narrow therapeutic index. The impact of such polymorphisms on drug plasma concentrations and the resulting dosing strategies are presented in this review, using the example of efavirenz (EFV).

METHODS

A structured literature search was performed to extract information pertaining to EFV metabolism and the influence of polymorphisms of CYP2B6, ethnicity, sex and drug interactions on plasma concentrations of EFV. The corresponding dosing strategies developed for carriers of specific CYP2B6 genotypes were also reviewed.

RESULTS

The polymorphic CYP2B6 enzyme, which is the major enzyme in the EFV metabolic pathway, is a key determinant for the significant inter-individual differences seen in EFV pharmacokinetics and pharmacodynamics (PKPD). Ethnic differences and the associated prevalence of CYP2B6 polymorphisms result in significant differences in the PKPD associated with a standard 600 mg per day dose of EFV, warranting dosage reduction in carriers of specific CYP2B6 polymorphisms. Drug interactions and auto-induction also influence EFV PKPD significantly.

CONCLUSION

Using EFV as an example of a drug with a narrow therapeutic index and a high inter-patient variability in plasma concentrations corresponding to a standard dose of the drug, this review demonstrates how genotyping of the primary metabolising enzyme can be useful for appropriate dosage adjustments in individuals. However, other variables such as drug interactions and auto-induction may necessitate plasma concentration measurements as well, prior to personalising the dose.

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.

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.