Effect of rifampin on steady-state pharmacokinetics of atazanavir with ritonavir in healthy volunteers

Pharmacokinetics and Safety of Twice-daily Ritonavir-boosted Atazanavir With Rifampicin

BACKGROUND

Critical drug-drug interactions (DDI) and hepatotoxicity complicate concurrent use of rifampicin and protease inhibitors. We investigated whether dose escalation of atazanavir/ritonavir could safely overcome the DDI with rifampicin.

METHODS

DERIVE (NCT04121195, EDCTP) was a dose-escalation trial in people with human immunodeficiency virus (HIV) on atazanavir/ritonavir-based antiretroviral therapy (ART) in Uganda. Four intensive pharmacokinetic (PK) visits were performed: PK1 300/100 mg OD (baseline); PK2 300/100 mg OD with rifampicin 600 mg; PK3 300/100 mg twice a day (BID) with rifampicin 600 mg OD; PK4 300/100 mg BID with rifampicin 1200 mg OD. Dolutegravir 50 mg BID throughout the study period ensured participants remained protected from subtherapeutic atazanavir concentrations. The data were interpreted with noncompartmental analysis. The target minimum concentration was atazanavir's protein-adjusted IC90 (PA-IC90), 0.014 mg/L.

RESULTS

We enrolled 26 participants (23 female) with median (range) age 44 (28-61) years and weight 67 (50-75) kg. Compared with PK1, atazanavir Ctau, and AUC were significantly reduced at PK2 by 96% and 85%, respectively. The escalation to BID dosing (PK3) reduced this difference in Ctau, and AUC24 to 18% lower and 8% higher, respectively. Comparable exposures were maintained with double doses of rifampicin. Lowest Ctau during PK1, PK3, and PK4 were 12.7-, 4.8-, and 8.6-fold higher than PA-IC90, respectively, whereas 65% of PK2 Ctau were below the limit of quantification (0.03 mg/L), hence likely below PA-IC90. No participant developed significant elevation of liver enzymes, reported a serious adverse event (SAE) or experienced rebound viraemia.

CONCLUSIONS

Twice daily atazanavir/ritonavir during rifampicin co-administration was well tolerated and achieved plasma concentrations above the target.

CLINICAL TRIALS REGISTRATION

NCT04121195. Registered on 09 October 2019, https://clinicaltrials.gov/ct2/show/NCT04121195.

HIV/Tuberculosis Coinfection in Pregnancy and the Postpartum Period

The convergence of Human Immunodeficiency Virus (HIV) and tuberculosis (TB) represents a considerable global public health challenge. The concurrent infection of HIV and TB in pregnant women not only intensifies the transmission of HIV from mother to fetus but also engenders adverse outcomes for maternal health, pregnancy, and infant well-being, necessitating the implementation of integrated strategies to effectively address and manage both diseases. In this article, we review the pathophysiology, clinical presentation, treatment, and management of HIV/TB coinfection during pregnancy, the postpartum period, and lactation and highlight the differences compared to the general population.

A Literature Review of Liver Function Test Elevations in Rifampin Drug-Drug Interaction Studies

Although rifampin drug–drug interaction (DDI) studies are routinely conducted, there have been instances of liver function test (LFT) elevations, warranting further evaluation. A literature review was conducted to identify studies in which combination with rifampin resulted in hepatic events and evaluate any similarities. Over 600 abstracts and manuscripts describing rifampin DDI studies were first evaluated, of which 30 clinical studies reported LFT elevations. Out of these, 11 studies included ritonavir in combination with other drug(s) in the rifampin DDI study. The number of subjects that were discontinued from treatment on these studies ranged from 0 to 71 (0–100% of subjects in each study). The number of subjects hospitalized for adverse events in these studies ranged from 0 to 41 (0–83.67% of subjects in each study). LFT elevations in greater than 50% of subjects were noted during the concomitant administration of rifampin with ritonavir‐boosted protease inhibitors and with lorlatinib; with labeled contraindication due to observed hepatotoxicity related safety findings only for saquinavir/ritonavir and lorlatinib. In the lorlatinib and ritonavir DDI studies, considerable LFT elevations were observed rapidly, typically within 24–72 h following co‐administration. A possible sequence effect has been speculated, where rifampin induction prior to administration of the combination may be associated with increased severity of the LFT elevations. The potential role of rifampin in the metabolic activation of certain drugs into metabolites with hepatic effects needs to be taken into consideration when conducting rifampin DDI studies, particularly those for which the metabolic profiles are not fully elucidated.

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.

Predicting Drug-Drug Interactions between Rifampicin and Ritonavir-Boosted Atazanavir Using PBPK Modelling

Objectives

The aim of this study was to simulate the drug–drug interaction (DDI) between ritonavir-boosted atazanavir (ATV/r) and rifampicin (RIF) using physiologically based pharmacokinetic (PBPK) modelling, and to predict suitable dose adjustments for ATV/r for the treatment of people living with HIV (PLWH) co-infected with tuberculosis.

Methods

A whole-body DDI PBPK model was designed using Simbiology 9.6.0 (MATLAB R2019a) and verified against reported clinical data for all drugs administered alone and concomitantly. The model contained the induction mechanisms of RIF and ritonavir (RTV), the inhibition effect of RTV for the enzymes involved in the DDI, and the induction and inhibition mechanisms of RIF and RTV on the uptake and efflux hepatic transporters. The model was considered verified if the observed versus predicted pharmacokinetic values were within twofold. Alternative ATV/r dosing regimens were simulated to achieve the trough concentration (C_trough) clinical cut-off of 150 ng/mL.

Results

The PBPK model was successfully verified according to the criteria. Simulation of different dose adjustments predicted that a change in regimen to twice-daily ATV/r (300/100 or 300/200 mg) may alleviate the induction effect of RIF on ATV C_trough, with > 95% of individuals predicted to achieve C_trough above the clinical cut-off.

Conclusions

The developed PBPK model characterized the induction-mediated DDI between RIF and ATV/r, accurately predicting the reduction of ATV plasma concentrations in line with observed clinical data. A change in the ATV/r dosing regimen from once-daily to twice-daily was predicted to mitigate the effect of the DDI on the C_trough of ATV, maintaining plasma concentration levels above the therapeutic threshold for most patients.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40262-021-01067-1.

Adoption of evidence-informed guidelines in prescribing protease inhibitors for HIV-Tuberculosis co-infected patients on rifampicin and effects on HIV treatment outcomes in Uganda

BACKGROUND

We aimed to determine how emerging evidence over the past decade informed how Ugandan HIV clinicians prescribed protease inhibitors (PIs) in HIV patients on rifampicin-based tuberculosis (TB) treatment and how this affected HIV treatment outcomes.

METHODS

We reviewed clinical records of HIV patients aged 13 years and above, treated with rifampicin-based TB treatment while on PIs between1st-January -2013 and 30th-September-2018 from twelve public HIV clinics in Uganda. Appropriate PI prescription during rifampicin-based TB treatment was defined as; prescribing doubled dose lopinavir/ritonavir- (LPV/r 800/200 mg twice daily) and inappropriate PI prescription as prescribing standard dose LPV/r or atazanavir/ritonavir (ATV/r).

RESULTS

Of the 602 patients who were on both PIs and rifampicin, 103 patients (17.1% (95% CI: 14.3-20.34)) received an appropriate PI prescription. There were no significant differences in the two-year mortality (4.8 vs. 5.7%, P = 0.318), loss to follow up (23.8 vs. 18.9%, P = 0.318) and one-year post TB treatment virologic failure rates (31.6 vs. 30.7%, P = 0.471) between patients that had an appropriate PI prescription and those that did not. However, more patients on double dose LPV/r had missed anti-retroviral therapy (ART) days (35.9 vs 21%, P = 0.001).

CONCLUSION

We conclude that despite availability of clinical evidence, double dosing LPV/r in patients receiving rifampicin-based TB treatment is low in Uganda's public HIV clinics but this does not seem to affect patient survival and viral suppression.

Safety and Pharmacokinetics of Double-Dose Lopinavir/Ritonavir + Rifampin Versus Lopinavir/Ritonavir + Daily Rifabutin for Treatment of Human Immunodeficiency Virus-Tuberculosis Coinfection

BACKGROUND

Protease inhibitor-based antiretroviral therapy may be used in resource-limited settings in persons with human immunodeficiency virus and tuberculosis (HIV-TB). Data on safety, pharmacokinetics/pharmacodynamics (PK/PD), and HIV-TB outcomes for lopinavir/ritonavir (LPV/r) used with rifampin (RIF) or rifabutin (RBT) are limited.

METHODS

We randomized adults with HIV-TB from July 2013 to February 2016 to arm A, LPV/r 400 mg/100 mg twice daily + RBT 150 mg/day; arm B, LPV/r 800 mg/200 mg twice daily + RIF 600 mg/day; or arm C, LPV/r 400 mg/100 mg twice daily + raltegravir (RAL) 400 mg twice daily + RBT 150 mg/day. All received two nucleoside reverse transcriptase inhibitors and other TB drugs. PK visits occurred on day 12 ± 2. Within-arm HIV-TB outcomes were summarized using proportions and 95% CIs; PK were compared using Wilcoxon tests.

RESULTS

Among 71 participants, 52% were women; 72% Black; 46% Hispanic; median age, 37 years; median CD4+ count, 130 cells/mm3; median HIV-1 RNA, 4.6 log10 copies/mL; 46% had confirmed TB. LPV concentrations were similar across arms. Pooled LPV AUC12 (157 203 hours × ng/mL) and Ctrough (9876 ng/mL) were similar to historical controls; RBT AUC24 (7374 hours × ng/mL) and Ctrough (208 ng/mL) were higher, although 3 participants in arm C had RBT Cmax <250 ng/mL. Proportions with week 48 HIV-1 RNA <400 copies/mL were 58%, 67%, and 61%, respectively, in arms A, B, and C.

CONCLUSIONS

Double-dose LPV/r+RIF and LPV/r+RBT 150mg/day had acceptable safety, PK and TB outcomes; HIV suppression was suboptimal but unrelated to PK. Faster RBT clearance and low Cmax in 3 participants on RBT+RAL requires further study.

Predictors of failure on second-line antiretroviral therapy with protease inhibitor mutations in Uganda

Introduction

Failure on second-line antiretroviral therapy (ART) with protease inhibitor (PI) mutations (VF-M) is on the rise. However, there is a paucity of information on the factors associated with this observation in low-income countries. Knowledge of underlying factors is critical if we are to minimize the number of PLHIV switched to costly third-line ART. Our study investigated the factors associated with VF-M.

Methods

We conducted a matched case–control analysis of patients' records kept at the Joint Clinical Research Center, starting from January 2008 to May 2018. We matched records of patients who failed the second-line ART with major PI mutations (cases) with records of patients who were virologically suppressed (controls) by a ratio of 1:3. Data analysis was conducted using STATA Version 14. Categorical variables were compared with the outcomes

failure on second-line ART with PI mutations using the Chi-square and Fisher's exact tests where appropriate. Conditional logistic regression for paired data was used to assess the association between the outcome and exposure variables, employing the backward model building procedure.

Results

Of the 340 reviewed patients' records, 53% were women, and 6.2% had previous tuberculosis treatment. Males (aOR = 2.58, [CI 1.42–4.69]), and patients concurrently on tuberculosis treatment while on second-line ART (aOR = 5.65, [CI 1.76–18.09]) had higher odds of VF-M. ART initiation between 2001 and 2015 had lower odds of VF-M relative to initiation before the year 2001.

Conclusion

Males and patients concomitantly on tuberculosis treatment while on second-line ART are at a higher risk of VF-M. HIV/AIDS response programs should give special attention to this group of people if we are to minimize the need for expensive third-line ART. We recommend more extensive, explorative studies to ascertain underlying factors.

Drug-drug interaction of atazanavir on UGT1A1-mediated glucuronidation of molidustat in human

Molidustat is an oral inhibitor of hypoxia‐inducible factor (HIF) prolyl‐hydroxylase enhancing the erythropoietin (EPO) response to HIF; it is in clinical development for the treatment of anaemia related to chronic kidney disease. The predominant role of glucuronidation for molidustat clearance (formation of N‐glucuronide metabolite M1) and subsequent renal excretion was confirmed in a human mass balance study, with about 85% of the drug being excreted as M1 in urine. The inhibitory effects of 176 drugs and xenobiotics from various compound classes on the UGT‐mediated glucuronidation of molidustat in human liver microsomes (HLMs) were investigated. Based on preclinical findings, glucuronidation of molidustat was predominantly mediated by the 5'‐diphospho‐glucuronosyltransferase (UGT) isoform UGT1A1. Therefore, atazanavir, which is a potent inhibitor of UGT1A1, was chosen for the evaluation of pharmacokinetics and EPO release following a single oral dose of 25 mg molidustat. Molidustat exposure increased about twofold upon coadministration with atazanavir when considering area under plasma concentration‐time curve from zero to infinity (AUC) and maximum plasma concentration (C_max). Baseline‐corrected increase of EPO was 14% and 34% for C_max and AUC (calculated over 24 hours), respectively. Coadministration of molidustat and atazanavir was well tolerated.

Pharmacokinetics of antiretroviral and tuberculosis drugs in children with HIV/TB co-infection: a systematic review

INTRODUCTION

Management of concomitant use of ART and TB drugs is difficult because of the many drug-drug interactions (DDIs) between the medications. This systematic review provides an overview of the current state of knowledge about the pharmacokinetics (PK) of ART and TB treatment in children with HIV/TB co-infection, and identifies knowledge gaps.

METHODS

We searched Embase and PubMed, and systematically searched abstract books of relevant conferences, following PRISMA guidelines. Studies not reporting PK parameters, investigating medicines that are not available any longer or not including children with HIV/TB co-infection were excluded. All studies were assessed for quality.

RESULTS

In total, 47 studies met the inclusion criteria. No dose adjustments are necessary for efavirenz during concomitant first-line TB treatment use, but intersubject PK variability was high, especially in children <3 years of age. Super-boosted lopinavir/ritonavir (ratio 1:1) resulted in adequate lopinavir trough concentrations during rifampicin co-administration. Double-dosed raltegravir can be given with rifampicin in children >4 weeks old as well as twice-daily dolutegravir (instead of once daily) in children older than 6 years. Exposure to some TB drugs (ethambutol and rifampicin) was reduced in the setting of HIV infection, regardless of ART use. Only limited PK data of second-line TB drugs with ART in children who are HIV infected have been published.

CONCLUSIONS

Whereas integrase inhibitors seem favourable in older children, there are limited options for ART in young children (<3 years) receiving rifampicin-based TB therapy. The PK of TB drugs in HIV-infected children warrants further research.

Prioritization of Anti-SARS-Cov-2 Drug Repurposing Opportunities Based on Plasma and Target Site Concentrations Derived from their Established Human Pharmacokinetics

There is a rapidly expanding literature on the in vitro antiviral activity of drugs that may be repurposed for therapy or chemoprophylaxis against severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2). However, this has not been accompanied by a comprehensive evaluation of the target plasma and lung concentrations of these drugs following approved dosing in humans. Accordingly, concentration 90% (EC90 ) values recalculated from in vitro anti-SARS-CoV-2 activity data was expressed as a ratio to the achievable maximum plasma concentration (Cmax ) at an approved dose in humans (Cmax /EC90 ratio). Only 14 of the 56 analyzed drugs achieved a Cmax /EC90 ratio above 1. A more in-depth assessment demonstrated that only nitazoxanide, nelfinavir, tipranavir (ritonavir-boosted), and sulfadoxine achieved plasma concentrations above their reported anti-SARS-CoV-2 activity across their entire approved dosing interval. An unbound lung to plasma tissue partition coefficient (Kp Ulung ) was also simulated to derive a lung Cmax /half-maximal effective concentration (EC50 ) as a better indicator of potential human efficacy. Hydroxychloroquine, chloroquine, mefloquine, atazanavir (ritonavir-boosted), tipranavir (ritonavir-boosted), ivermectin, azithromycin, and lopinavir (ritonavir-boosted) were all predicted to achieve lung concentrations over 10-fold higher than their reported EC50 . Nitazoxanide and sulfadoxine also exceeded their reported EC50 by 7.8-fold and 1.5-fold in lung, respectively. This analysis may be used to select potential candidates for further clinical testing, while deprioritizing compounds unlikely to attain target concentrations for antiviral activity. Future studies should focus on EC90 values and discuss findings in the context of achievable exposures in humans, especially within target compartments, such as the lungs, in order to maximize the potential for success of proposed human clinical trials.

The crosstalk between antiretrovirals pharmacology and HIV drug resistance

INTRODUCTION

The clinical development of antiretroviral drugs has been followed by a rapid and concomitant development of HIV drug resistance. The development and spread of HIV drug resistance is due on the one hand to the within-host intrinsic HIV evolutionary rate and on the other to the wide use of low genetic barrier antiretrovirals.

AREAS COVERED

We searched PubMed and Embase on 31 January 2020, for studies reporting antiretroviral resistance and pharmacology. In this review, we assessed the molecular target and mechanism of drug resistance development of the different antiretroviral classes focusing on the currently approved antiretroviral drugs. Then, we assessed the main pharmacokinetic/pharmacodynamic of the antiretrovirals. Finally, we retraced the history of antiretroviral treatment and its interconnection with antiretroviral worldwide resistance development both in , and middle-income countries in the perspective of 90-90-90 World Health Organization target.

EXPERT OPINION

Drug resistance development is an invariably evolutionary driven phenomenon, which challenge the 90-90-90 target. In high-income countries, the antiretroviral drug resistance seems to be stable since the last decade. On the contrary, multi-intervention strategies comprehensive of broad availability of high genetic barrier regimens should be implemented in resource-limited setting to curb the rise of drug resistance.

The Effect of Rifampin on the Pharmacokinetics and Safety of Lorlatinib: Results of a Phase One, Open-Label, Crossover Study in Healthy Participants

INTRODUCTION

Lorlatinib is a third-generation tyrosine kinase inhibitor approved for the treatment of anaplastic lymphoma kinase (ALK)-positive metastatic non-small cell lung cancer; cytochrome P450 (CYP) 3A plays an important role in the metabolism of lorlatinib.

METHODS

This phase 1, open-label, two-period, crossover study estimated the effect of oral rifampin (a strong CYP3A inducer) on the pharmacokinetics and safety of oral lorlatinib (NCT02804399). Healthy participants received single-dose lorlatinib 100 mg in period 1 followed by rifampin 600 mg/day (days 1-12) and single-dose lorlatinib 100 mg (day 8) in period 2. Blood samples were collected for 120 h after each dose of lorlatinib.

RESULTS

When a single dose of lorlatinib was administered during daily dosing with rifampin (period 2), the area under the plasma concentration-time profile extrapolated to infinity (AUC_inf) and maximum plasma concentration (C_max) of lorlatinib were 14.74% [90% confidence interval (CI) 12.78%, 17.01%] and 23.88% (90% CI 21.58%, 26.43%), respectively, of those in period 1 (lorlatinib alone). A single dose of lorlatinib was well tolerated in period 1, but elevations in transaminase values were observed in all participants (grade 2-4 in 11 participants) within 1-3 days after a single dose of lorlatinib was administered with ongoing rifampin in period 2. Rifampin dosing was therefore halted. Transaminase levels subsequently returned to normal (median time to recovery: 15 days). No elevations in bilirubin were observed.

CONCLUSIONS

The addition of a single dose of lorlatinib to daily dosing with rifampin significantly reduced lorlatinib plasma exposure relative to a single dose of lorlatinib administered alone and was associated with severe but self-limiting transaminase elevations in all healthy participants. These observations support the contraindication in the product label against concomitant use of lorlatinib with all strong CYP3A inducers.

TRIAL REGISTRATION

ClinicalTrials.gov identifier, NCT02804399.

A Comprehensive Framework for Physiologically-Based Pharmacokinetic Modeling in Matlab

Physiologically-based pharmacokinetic (PBPK) models are useful tools to predict clinical scenarios for special populations for whom there are high hurdles to conduct clinical trials such as children or the elderly. However, the coding of a PBPK model in a mathematical programming language can be challenging. This tutorial illustrates how to build a whole-body PBPK model in Matlab to answer specific pharmacological questions involving drug disposition and magnitudes of drug-drug interactions in different patient populations.

Tuberculosis-HIV treatment with rifampicin or rifabutin: are the outcomes different?

BACKGROUND

Rifamycins are a group of antibiotics mainly used in the treatment of tuberculosis (TB), however they interact with antiretroviral therapy (ART). Rifabutin allows more regimens options for concomitant imunodeficiency virus (HIV) treatment compared to rifampicin.

OBJECTIVE

Compare the outcomes of TB-HIV co-infected patients who used rifampicin or rifabutin.

METHODS

We analysed data from a prospective cohort study at National Institute of Infectious Diseases Evandro Chagas, Rio de Janeiro (RJ), Brazil. Patients who were treated for TB and HIV with rifampicin or rifabutin, from February 2011 to September 2016 were included.

FINDINGS

There were 130 TB-HIV patients, of whom 102 were treated with rifampicin and 28 with rifabutin. All patients in the rifabutin-treated group and 55% of the rifampicin-treated group patients were ART-experienced. Patients treated with rifampicin had similar abandon and cure rates, interruptions in treatment due to adverse reactions, immune reconstitution inflammatory syndrome and a similar mortality rate as those treated with rifabutin. However, rifampicin-treated patients had higher CD4 counts and more frequently undetectable HIV viral load by the end of treatment (67% versus 18%, p < 0.001) compared to rifabutin-treated patients, even when only ART-experienced patients were evaluated (66,6% versus 36,3%, p = 0.039).

CONCLUSIONS

Patients who used rifabutin had worst immune and virological control. This group had more ART-experienced patients. New and simpler regimens are needed for patients who do not respond to previous antiretroviral therapies.

Safety and Efficacy of Atazanavir Powder and Ritonavir in HIV-1-Infected Infants and Children From 3 Months to <11 Years of Age: The PRINCE-2 Study

BACKGROUND

Novel antiretroviral formulations that are palatable, safe, and effective are needed for infants and children.

METHODS

PRINCE-2 is an ongoing clinical trial assessing safety, efficacy, and palatability of once-daily atazanavir powder formulation boosted with ritonavir (ATV + RTV) plus optimized dual nucleos(t)ide reverse transcriptase inhibitors therapy in antiretroviral-naïve/experienced children with screening HIV-1 RNA ≥1000 copies/mL. Children 3 months to <11 years received ATV + RTV by 5 baseline weight bands: 5 to <10 kg = 150/80 mg; 5 to <10 kg = 200/80 mg; 10 to <15 kg = 200/80 mg; 15 to <25 kg = 250/80 mg; and 25 to <35 kg = 300/100 mg.

RESULTS

Of 99 treated children, 83.8% and 59.6% remained on ATV powder until 24 and 48 weeks, respectively. Through 48 weeks, the most common adverse events were upper respiratory tract infections (33.3%), gastroenteritis (28.3%), vomiting (21.2%) and hyperbilirubinemia (18.2%; none leading to treatment discontinuation). Serious adverse events occurred in 20.2% of patients. Laboratory grade 3-4 hyperbilirubinemia occurred in 9.2% and elevated total/pancreatic amylase in 33.7%/3.1%. At week 24, proportions with virologic suppression (HIV-1 RNA <50 copies/mL; intention-to-treat analysis) across weight bands were 10/23 (43.5%), 2/12 (16.5%), 10/21 (47.6%), 19/35 (54.3%) and 5/8 (62.5%), respectively. Virologic suppression was similar in antiretroviral-naïve/experienced patients and lowest in the 5 to <10 kg = 200/80 mg group, likely because of higher baseline HIV-1 RNA and discontinuation (66.7%). Overall, virologic suppression at weeks 24 (46.5%) and 48 (43.0%) was comparable. At week 48, 83.3% and 74.1% of caregivers reported no trouble giving ATV powder and RTV, respectively.

CONCLUSIONS

ATV powder palatability, efficacy and lack of unexpected safety findings support its use for HIV-1-infected children ≥3 months to <11 years.

Predictors of switch to and early outcomes on third-line antiretroviral therapy at a large public-sector clinic in Johannesburg, South Africa

BACKGROUND

While efficacy data exist, there are limited data on the outcomes of patients on third-line antiretroviral therapy (ART) in sub-Saharan Africa in actual practice. Being able to identify predictors of switch to third-line ART will be essential for planning for future need. We identify predictors of switch to third-line ART among patients with significant viraemia on a protease inhibitor (PI)-based second-line ART regimen. Additionally, we describe characteristics of all patients on third-line at a large public sector HIV clinic and present their early outcomes.

METHODS

Retrospective analysis of adults (≥ 18 years) on a PI-based second-line ART regimen at Themba Lethu Clinic, Johannesburg, South Africa as of 01 August 2012, when third-line treatment became available in South Africa, with significant viraemia on second-line ART (defined as at least one viral load ≥ 1000 copies/mL on second-line ART after 01 August 2012) to identify predictors of switch to third-line (determined by genotype resistance testing). Third-line ART was defined as a regimen containing etravirine, raltegravir or ritonavir boosted darunavir, between August 2012 and January 2016. To assess predictors of switch to third-line ART we used Cox proportional hazards regression among those with significant viraemia on second-line ART after 01 August 2012. Then among all patients on third-line ART we describe viral load suppression, defined as a viral load < 400 copies/mL, after starting third-line ART.

RESULTS

Among 719 patients in care and on second-line ART as of August 2012 (with at least one viral load ≥ 1000 copies/mL after 01 August 2012), 36 (5.0% over a median time of 54 months) switched to third-line. Time on second-line therapy (≥ 96 vs. < 96 weeks) (adjusted Hazard Ratio (aHR): 2.53 95% CI 1.03-6.22) and never reaching virologic suppression while on second-line ART (aHR: 3.37 95% CI 1.47-7.73) were identified as predictors of switch. In a separate cohort of patients on third-line ART, 78.3% (47/60) and 83.3% (35/42) of those in care and with a viral load suppressed their viral load at 6 and 12 months, respectively.

CONCLUSIONS

Our results show that the need for third-line is low (5%), but that patients' who switch to third-line ART have good early treatment outcomes and are able to suppress their viral load. Adherence counselling and resistance testing should be prioritized for patients that are at risk of failure, in particular those who never suppress on second-line and those who have been on PI-based regimen for extended periods.

Interaction of Rifampin and Darunavir-Ritonavir or Darunavir-Cobicistat In Vitro

Treatment of HIV-infected patients coinfected with Mycobacterium tuberculosis is challenging due to drug-drug interactions (DDIs) between antiretrovirals (ARVs) and antituberculosis (anti-TB) drugs. The aim of this study was to quantify the effect of cobicistat (COBI) or ritonavir (RTV) in modulating DDIs between darunavir (DRV) and rifampin (RIF) in a human hepatocyte-based in vitro model. Human primary hepatocyte cultures were incubated with RIF alone or in combination with either COBI or RTV for 3 days, followed by coincubation with DRV for 1 h. The resultant DRV concentrations were quantified by high-performance liquid chromatography with UV detection, and the apparent intrinsic clearance (CL_int.app.) of DRV was calculated. Both RTV and COBI lowered the RIF-induced increases in CL_int.app. in a concentration-dependent manner. Linear regression analysis showed that log₁₀ RTV and log₁₀ COBI concentrations were associated with the percent inhibition of RIF-induced elevations in DRV CL_int.app., where β was equal to -234 (95% confidence interval [CI] = -275 to -193; P < 0.0001) and -73 (95% CI = -89 to -57; P < 0.0001), respectively. RTV was more effective in lowering 10 μM RIF-induced elevations in DRV CL_int.app. (half-maximal [50%] inhibitory concentration [IC₅₀] = 0.025 μM) than COBI (IC₅₀ = 0.223 μM). Incubation of either RTV or COBI in combination with RIF was sufficient to overcome RIF-induced elevations in DRV CL_int.app., with RTV being more potent than COBI. These data provide the first in vitro experimental insight into DDIs between RIF and COBI-boosted or RTV-boosted DRV and will be useful to inform physiologically based pharmacokinetic (PBPK) models to aid in optimizing dosing regimens for the treatment of patients coinfected with HIV and M. tuberculosis.

Virological Outcomes of Second-line Protease Inhibitor-Based Treatment for Human Immunodeficiency Virus Type 1 in a High-Prevalence Rural South African Setting: A Competing-Risks Prospective Cohort Analysis

Background

Second-line antiretroviral therapy (ART) based on ritonavir-boosted protease inhibitors (bPIs) represents the only available option after first-line failure for the majority of individuals living with human immunodeficiency virus (HIV) worldwide. Maximizing their effectiveness is imperative.

Methods

This cohort study was nested within the French National Agency for AIDS and Viral Hepatitis Research (ANRS) 12249 Treatment as Prevention (TasP) cluster-randomized trial in rural KwaZulu-Natal, South Africa. We prospectively investigated risk factors for virological failure (VF) of bPI-based ART in the combined study arms. VF was defined by a plasma viral load >1000 copies/mL ≥6 months after initiating bPI-based ART. Cumulative incidence of VF was estimated and competing risk regression was used to derive the subdistribution hazard ratio (SHR) of the associations between VF and patient clinical and demographic factors, taking into account death and loss to follow-up.

Results

One hundred one participants contributed 178.7 person-years of follow-up. Sixty-five percent were female; the median age was 37.4 years. Second-line ART regimens were based on ritonavir-boosted lopinavir, combined with zidovudine or tenofovir plus lamivudine or emtricitabine. The incidence of VF on second-line ART was 12.9 per 100 person-years (n = 23), and prevalence of VF at censoring was 17.8%. Thirteen of these 23 (56.5%) virologic failures resuppressed after a median of 8.0 months (interquartile range, 2.8-16.8 months) in this setting where viral load monitoring was available. Tuberculosis treatment was associated with VF (SHR, 11.50 [95% confidence interval, 3.92-33.74]; P < .001).

Conclusions

Second-line VF was frequent in this setting. Resuppression occurred in more than half of failures, highlighting the value of viral load monitoring of second-line ART. Tuberculosis was associated with VF; therefore, novel approaches to optimize the effectiveness of PI-based ART in high-tuberculosis-burden settings are needed.

Clinical Trials Registration

NCT01509508.

Coadministration of Rifampin Significantly Reduces Odanacatib Concentrations in Healthy Subjects

This open-label 2-period study assessed the effect of multiple-dose administration of rifampin, a strong cytochrome P450 3A (CYP3A) and P-glycoprotein inducer, on the pharmacokinetics of odanacatib, a cathepsin K inhibitor. In period 1, 12 healthy male subjects (mean age, 30 years) received a single dose of odanacatib 50 mg on day 1, followed by a 28-day washout. In period 2, subjects received rifampin 600 mg/day for 28 days; odanacatib 50 mg was coadministered on day 14. Blood samples for odanacatib pharmacokinetics were collected at predose and on day 1 of period 1 and day 14 of period 2. Coadministration of odanacatib and rifampin significantly reduced odanacatib exposure. The odanacatib AUC_0-∞ geometric mean ratio (90% confidence interval) of odanacatib + rifampin/odanacatib alone was 0.13 (0.11-0.16). The harmonic mean ± jackknife standard deviation apparent terminal half-life (t_½ ) was 71.6 ± 10.2 hours for odanacatib alone and 16.0 ± 3.4 hours for odanacatib + rifampin, indicating greater odanacatib clearance following coadministration with rifampin. Samples were collected in period 2 during rifampin dosing (days 1, 14, and 28) and after rifampin discontinuation (days 35, 42, and 56) to evaluate the ratio of plasma 4β-hydroxycholesterol to total serum cholesterol as a CYP3A4 induction biomarker; the ratio increased ∼5-fold over 28 days of daily dosing with 600 mg rifampin, demonstrating sensitivity to CYP3A4 induction.

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.

Tuberculosis: opportunities and challenges for the 90-90-90 targets in HIV-infected children

INTRODUCTION

In 2014 the Joint United Nations Programme on HIV/AIDS defined the ambitious 90-90-90 targets for 2020, in which 90% of people living with HIV must be diagnosed, 90% of those diagnosed should be on sustained therapy and 90% of those on therapy should have an undetectable viral load. Children are considered to be a key focus population for these targets. This review will highlight key components of the epidemiology, prevention and treatment of tuberculosis (TB) in HIV-infected children in the era of increasing access to antiretroviral therapy (ART) and their relation to the 90-90-90 targets.

DISCUSSION

The majority of HIV-infected children live in countries with a high burden of TB. In settings with a high burden of both diseases such as in sub-Saharan Africa, up to 57% of children diagnosed with and treated for TB are HIV-infected. TB results in substantial morbidity and mortality in HIV-infected children, so preventing TB and optimizing its treatment in HIV-infected children will be important to ensuring good long-term outcomes. Prevention of TB can be achieved by increasing access to ART to both children and adults, and appropriate provision of isoniazid preventative therapy. Co-treatment of HIV and TB is complicated by drug-drug interactions particularly due to the use of rifampicin; these may compromise virologic outcomes if appropriate corrective actions are not taken. There remain substantial operational challenges, and improved integration of paediatric TB and HIV services, including with antenatal and routine under-five care, is an important priority.

CONCLUSIONS

TB may be an important barrier to achievement of the 90-90-90 targets, but specific attention to TB care in HIV-infected children may provide important opportunities to enhance the care of both TB and HIV in children.

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.

Treatment optimization in patients co-infected with HIV and Mycobacterium tuberculosis infections: focus on drug-drug interactions with rifamycins

Tuberculosis (TB) and HIV continue to be two of the major causes of morbidity and mortality in the world, and together are responsible for the death of millions of people every year. There is overwhelming evidence to recommend that patients with TB and HIV co-infection should receive concomitant therapy of both conditions regardless of the CD4 cell count level. The principles for treatment of active TB disease in HIV-infected patients are the same as in HIV-uninfected patients. However, concomitant treatment of both conditions is complex, mainly due to significant drug-drug interactions between TB and HIV drugs. Rifamycins are potent inducers of the cytochrome P450 (CYP) pathway, leading to reduced (frequently sub-therapeutic) plasma concentrations of some classes of antiretrovirals. Rifampicin is also an inducer of the uridine diphosphate glucuronosyltransferase (UGT) 1A1 enzymes and interferes with drugs, such as integrase inhibitors, that are metabolized by this metabolic pathway. Rifampicin is also an inducer of the adenosine triphosphate (ATP) binding cassette transporter P-glycoprotein, which may also lead to decreased bioavailability of concomitantly administered antiretrovirals. On the other side, rifabutin concentrations are affected by the antiretrovirals that induce or inhibit CYP enzymes. In this review, the pharmacokinetic interactions, and the relevant clinical consequences, of the rifamycins-rifampicin, rifabutin, and rifapentine-with antiretroviral drugs are reviewed and discussed. A rifampicin-based antitubercular regimen and an efavirenz-based antiretroviral regimen is the first choice for treatment of TB/HIV co-infected patients. Rifabutin is the preferred rifamycin to use in HIV-infected patients on a protease inhibitor-based regimen; however, the dose of rifabutin needs to be reduced to 150 mg daily. More information is required to select optimal treatment regimens for TB/HIV co-infected patients whenever efavirenz cannot be used and rifabutin is not available. Despite significant pharmacokinetic interactions between antiretrovirals and antitubercular drugs, adequate clinical response of both infections can be achieved with an acceptable safety profile when the pharmacological characteristics of drugs are known, and appropriate combination regimens, dosing, and timing of initiation are used. However, more clinical research is needed for newer drugs, such as rifapentine and the recently introduced integrase inhibitor antiretrovirals, and for specific population groups, such as children, pregnant women, and patients affected by multidrug-resistant TB.

Pharmacokinetics and 48 week efficacy of adjusted dose indinavir/ritonavir in rifampicin-treated HIV/tuberculosis-coinfected patients: a pilot study

HIV/tuberculosis (HIV/TB)-coinfected patients intolerant/resistant to nonnucleoside reverse transcriptase inhibitors (NNRTIs) have limited treatment options. We evaluated the pharmacokinetics (PK)/safety/efficacy of an adjusted dose of indinavir/ritonavir (IDV/r) 600/100 mg plus two NRTIs in HIV/TB-coinfected Thais receiving rifampicin-based anti-TB treatment. This was a prospective, open-label study. Eighteen Thai, HIV/TB-coinfected patients between 18 and 60 years were recruited. IDV/r 600 mg/100 mg plus lamivudine and stavudine were administered every 12 h (bid). When rifampicin was stopped, IDV/r was reduced to 400/100 mg BID. Clinical outcomes, adverse events, and concomitant drugs were intensively collected. Intensive 12-h PK was performed after 2 weeks of IDV/r while on rifampicin. Samples were collected: predosing and 1, 2, 3, 4, 6, 8, 10, and 12 h after drug intake. The median body weight was 55 kg. The median CD4 was 26 cells/μl. The median HIV RNA was 5.05 log(10) copies/ml. Then 15/18 underwent intensive PK at week 2. The median time between initiating rifampicin and IDV/r was 4.5 months. The median duration of rifampicin during study (rifampicin/IDV/r together) was 15.6 weeks. All received a total of 9 months of antituberculous drugs. The geometric means (GM) of indinavir AUC(0-12) and C(12) were 8.11 mg*h/liter and 0.03 mg/liter, respectively. After stopping rifampicin and reducing IDV/r to 400/100 bid, the GM indinavir C(12) increased to 0.68 mg/liter (p=0.004). In all, 8/18 (44%) had asymptomatic ALT elevation and 2/18 (11%) had symptomatic hepatotoxicity requiring IDV/r discontinuation. All 13 patients who remained on IDV/r treatment had HIV RNA <50 copies/ml at 48 weeks. Concomitant use of rifampicin and IDV/r resulted in subtherapeutic indinavir concentrations. Although 44% of them developed asymptomatic Grade 3/4 transaminitis, the rate of study drug discontinuation due to hepatotoxicity was low. Despite good virological outcome in our cohort, prolonged exposure to subtherapeutic indinavir concentrations may lead to treatment failure.

Coadministration of lopinavir/ritonavir and rifampicin in HIV and tuberculosis co-infected adults in South Africa

Background

In HIV-infected patients receiving rifampicin-based treatment for tuberculosis (TB), the dosage of lopinavir/ritonavir (LPV/r) is adjusted to prevent sub-therapeutic lopinavir concentrations. In this setting, South African clinicians were advised to administer super-boosted LPV/r (400 mg/400 mg) twice daily, instead of standard dosed LPV/r (400 mg/100 mg) twice daily. We sought to determine – in routine practice – the tolerability and HIV treatment outcomes associated with super-boosted LPV/r compared to unadjusted LPV/r in combination with rifampicin-based TB treatment.

Methodology/Principle Findings

We conducted a retrospective review of HIV-infected patients who receiving second-line ART with a LPV/r-containing regimen who required concomitant TB treatment. We identified 29 patients; the median age was 36 years (IQR 29–40), 22 (76%) were female, the median CD4 cell count and viral load at first-line ART failure was 86 cells/mm³ (IQR 21–159) and 39,457 copies/mL (IQR 6,025–157,500), respectively. According to physician preference, 15 (52%) of 29 patients received super-boosted LPV/r (400 mg/400 mg) every 12 hours during TB treatment and 14 (48%) of 29 patients received standard dose LPV/r (400 mg/100 mg) twice daily during TB treatment. Among patients who received super-boosted LPV/r there was a trend towards a higher rate of symptomatic transaminitis (27% vs. 7%; p = 0.3), gastrointestinal toxicity (20% vs. 0%; p = 0.2) and a significantly increased need for treatment discontinuation (47% vs. 7%; p = 0.035. The durability of coadministered treatment was significantly shorter in patients who received super-boosted lopinavir/ritonavir with TB treatment compared to patients who received standard lopinavir/ritonavir dosing (log rank, P = 0.036). The rate of virologic failure was not higher in patients with unadjusted LPV/r dosing.

Conclusions/Significance

We observed a high rate of toxicity and need for treatment discontinuation among patients on standard rifampicin-based TB treatment who received super-boosted LPV/r.

TB and HIV Therapeutics: Pharmacology Research Priorities

An unprecedented number of investigational drugs are in the development pipeline for the treatment of tuberculosis. Among patients with tuberculosis, co-infection with HIV is common, and concurrent treatment of tuberculosis and HIV is now the standard of care. To ensure that combinations of anti-tuberculosis drugs and antiretrovirals are safe and are tested at doses most likely to be effective, selected pharmacokinetic studies based on knowledge of their metabolic pathways and their capacity to induce or inhibit metabolizing enzymes of companion drugs must be conducted. Drug interaction studies should be followed up by evaluations in larger populations to evaluate safety and pharmacodynamics more fully. Involving patients with HIV in trials of TB drugs early in development enhances the knowledge gained from the trials and will ensure that promising new tuberculosis treatments are available to patients with HIV as early as possible. In this review, we summarize current and planned pharmacokinetic and drug interaction studies involving investigational and licensed tuberculosis drugs and antiretrovirals and suggest priorities for tuberculosis-HIV pharmacokinetic, pharmacodynamic, and drug-drug interaction studies for the future. Priority studies for children and pregnant women with HIV and tuberculosis co-infection are briefly discussed.

Population pharmacokinetics of atazanavir/ritonavir in HIV-1-infected children and adolescents

AIMS

To investigate atazanavir (ATV) population pharmacokinetics in children and adolescents, establish factors that influence ATV pharmacokinetics and investigate the ATV exposure after recommended doses.

METHODS

Atazanavir concentrations were measured in 51 children/adolescents during a mean therapeutic monitoring follow up of 6.6 months. A total of 151 ATV plasma concentrations were obtained, and a population pharmacokinetic model was developed with NONMEM. Patients received ATV alone or boosted with ritonavir.

RESULTS

Atazanavir pharmacokinetics was best described by a one-compartment model with first-order absorption and elimination. The effect of bodyweight was added on both apparent elimination clearance (CL/F) and volume of distribution using allometric scaling. Atazanavir CL/F was reduced by ritonavir by 45%. Tenofovir disoproxil fumarate (TDF) co-medication (300 mg) increased significantly by 25% the atazanavir/ritonavir (ATV/r) CL/F. Mean ATV/r CL/F values with or without TDF were 8.9 and 7.1 L h(-1) (70 kg)(-1), respectively. With the recommended 250/100 mg and 300/100 mg ATV/r doses, the exposure was higher than the mean adult steady-state exposure in the bodyweight range of 32-50 kg.

CONCLUSIONS

To target the mean adult exposure, children should receive the following once-daily ATV/r dose: 200/100 mg from 25 to 39 kg, 250/100 mg from 39 to 50 kg and 300/100 mg above 50 kg. When 300 mg TDF is co-administered, children should receive (ATV/r) at 250/100 mg between 35 and 39 kg, then 300/100 mg over 39 kg.

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.

Pharmacokinetic drug interactions of antimicrobial drugs: a systematic review on oxazolidinones, rifamycines, macrolides, fluoroquinolones, and Beta-lactams

Like any other drug, antimicrobial drugs are prone to pharmacokinetic drug interactions. These drug interactions are a major concern in clinical practice as they may have an effect on efficacy and toxicity. This article provides an overview of all published pharmacokinetic studies on drug interactions of the commonly prescribed antimicrobial drugs oxazolidinones, rifamycines, macrolides, fluoroquinolones, and beta-lactams, focusing on systematic research. We describe drug-food and drug-drug interaction studies in humans, affecting antimicrobial drugs as well as concomitantly administered drugs. Since knowledge about mechanisms is of paramount importance for adequate management of drug interactions, the most plausible underlying mechanism of the drug interaction is provided when available. This overview can be used in daily practice to support the management of pharmacokinetic drug interactions of antimicrobial drugs.

Antiretroviral therapy responses among children attending a large public clinic in Soweto, South Africa

BACKGROUND

Antiretroviral therapy (ART) access with successful outcomes for children is expanding in resource-limited countries. The aim of this study was to determine treatment responses of children in a routine setting where first-line therapy with lopinavir/ritonavir is routinely included for young children.

METHODS

Outpatient records of children who initiated ART between April 2004 and March 2008 at a government clinic in Soweto were reviewed. Children <3 years initiated ART with lopinavir/ritonavir and those ≥ 3 years initiated with efavirenz-containing regimens.

RESULTS

ART was initiated at a median age of 4.3 years, 28.6% also received tuberculosis treatment. During 3155 child-years of follow-up (median follow-up 17 months), 132 children (6%) died giving a mortality rate of 4.2 (95% confidence interval: 3.5, 5.0) deaths per 100 child-years. By 12 and 24 months, 84% and 96% of children achieved virologic suppression. The proportion of children with viral rebound increased from 5.4% to 16.3% at 24 and 36 months from start of ART. Younger children (receiving lopinavir/ritonavir-based first-line therapy) with higher viral loads suppressed more slowly and were more likely to die. Children who were started on treatment for tuberculosis at the time of viral suppression were more likely to have virologic rebound.

CONCLUSION

Despite good treatment outcomes overall, children with advanced disease at ART initiation had poorer outcomes, particularly those <3 years of age, most of whom were treated with lopinavir/ritonavir-containing therapy. The increasing risk of viral rebound over time for the whole cohort is concerning, given currently limited available treatment options for children.

Initiating antiretrovirals during tuberculosis treatment: a drug safety review

INTRODUCTION

Integrating HIV and tuberculosis (TB) treatment can reduce mortality substantially. Practical barriers to treatment integration still exist and include safety concerns related to concomitant drug use because of drug interactions and additive toxicities. Altered therapeutic concentrations may influence the chances of treatment success or toxicity.

AREAS COVERED

The available data on drug-drug interactions between the rifamycin class of anti-mycobacterials and the non-nucleoside reverse transcriptase inhibitor and the protease inhibitor classes of antiretrovirals are discussed with recommendations for integrated use. Additive drug toxicities, the impact of immune reconstitution inflammatory syndrome (IRIS) and the latest data on survival benefits of integrating treatment are elucidated.

EXPERT OPINION

Deferring treatment of HIV to avoid drug interactions with TB treatment or the occurrence of IRIS is not necessary. In the integrated management of TB-HIV co-infection, rational drug combinations aimed at reducing toxicities while effecting TB cure and suppressing HIV viral load are possible.

Antiretroviral therapy outcomes in HIV-infected children after adjusting protease inhibitor dosing during tuberculosis treatment

BACKGROUND

Modification of ritonavir-boosted lopinavir (LPV/r)-based antiretroviral therapy is required for HIV-infected children co-treated for tuberculosis (TB). We aimed to determine virologic and toxicity outcomes among TB/HIV co-treated children with the following modifications to their antiretroviral therapy (ART): (1) super-boosted LPV/r, (2) double-dose LPV/r or (3) ritonavir.

METHODS AND FINDINGS

A medical record review was conducted at two clinical sites in Johannesburg, South Africa. The records of children 6-24 months of age initiating LPV/r-based therapy were reviewed. Children co-treated for TB were categorized based on the modifications made to their ART regimen and were compared to children of the same age at each site not treated for TB. Included are 526 children, 294 (56%) co-treated for TB. All co-treated children had more severe HIV disease, including lower CD4 percents and worse growth indicators, than comparisons. Children in the super-boosted group (n = 156) were as likely to be virally suppressed (<400 copies/ml) at 6 months as comparisons (69.2% vs. 74.8%, p = 0.36). Children in the double-dose (n = 47) and ritonavir groups (n = 91) were significantly less likely to be virally suppressed at 6 months (53.1% and 49.3%) than comparisons (74.8% and 82.1%; p = 0.02 and p<0.0001, respectively). At 12 months only children in the ritonavir group still had lower rates of virological suppression relative to comparisons (63.9% vs 83.3% p<0.05). Grade 1 or greater ALT elevations were more common in the super-boosted (75%) than double-dose (54.6%) or ritonavir (33.9%) groups (p = 0.09 and p<0.0001) but grade 3/4 elevations were observed in 3 (13.6%) of the super-boosted, 7 (15.9%) of the double-dose and 5 (8.9%) of the ritonavir group (p = 0.81 and p = 0.29).

CONCLUSION

Good short-term virologic outcomes were achieved in children co-treated for TB and HIV who received super-boosted LPV/r. Treatment limiting toxicity was rare. Strategies for increased dosing of LPV/r with TB treatment warrant further investigation.

HIV-infected adolescents: relationship between atazanavir plasma levels and bilirubin concentrations

The use of atazanavir (ATV) in adolescents infected with human immunodeficiency virus was analyzed in this study. ATV morning plasma concentrations were determined during regular visits to the outpatient department. Results showed that bilirubin levels were higher among patients with higher ATV plasma concentrations (p = .018). Monitoring plasma levels of ATV could avoid toxicity in these patients.

Initial response to protease-inhibitor-based antiretroviral therapy among children less than 2 years of age in South Africa: effect of cotreatment for tuberculosis

BACKGROUND

South African guidelines recommend protease-inhibitor-based antiretroviral therapy (ART) with lopinavir-ritonavir for human immunodeficiency virus (HIV)-infected children <36 months of age. We investigated factors associated with viral suppression and mortality among young children initiating ART.

METHODS

Treatment-naive, ART-eligible, HIV-infected children (aged 6-104 weeks) were enrolled in an ART strategies trial in South Africa and initiated protease-inhibitor-based ART. Mortality and the probability of viral suppression (defined as HIV RNA load of <400 copies/mL) by 39 weeks after ART initiation were investigated.

RESULTS

Of 254 children who initiated ART, 99 (39%) were cotreated for tuberculosis during follow-up. The mortality rate was 14%. Factors predicting mortality were lower pre-ART weight-for-age z score and higher HIV RNA load. By 39 weeks, 84% of surviving children achieved viral suppression. Children who were not cotreated for tuberculosis were more likely to achieve viral suppression (94.8%) than were children who were receiving cotreatment at ART initiation (74.2%) or who started tuberculosis cotreatment after ART initiation (51.6%; P < .001). Other factors predicting lower probability of viral suppression were lower pre-ART weight- and length-for-age z score, higher HIV RNA load, and World Health Organization disease stage.

CONCLUSION

High rates of viral suppression can be achieved among infants and young children who initiate protease-inhibitor-based ART. Cotreatment for tuberculosis reduced viral suppression. How best to treat HIV-infected children who require tuberculosis treatment warrants urgent investigation.

Antiretroviral therapy in developing countries: pharmacologic considerations

PURPOSE OF REVIEW

This article reviews recent studies in the field of clinical pharmacology of antiretroviral drugs and highlights the relevance of the findings to clinical practice in developing countries.

RECENT FINDINGS

Differences in antiretroviral pharmacokinetics are associated with polymorphisms of genes encoding drug metabolizing enzymes. Inadequate concentrations of antiretrovirals in children are common. A study in African children found subtherapeutic concentrations in 40% of patients receiving efavirenz at recommended doses.

SUMMARY

Recent findings on the pharmacokinetics of antiretroviral agents relevant to clinical practice in developing countries are reviewed. Widespread poverty impacts negatively on HIV/AIDS treatment and prevention efforts. Improved access to treatment, social and economic support and pharmacology research in target populations are needed.

Hepatotoxicity and gastrointestinal intolerance when healthy volunteers taking rifampin add twice-daily atazanavir and ritonavir

BACKGROUND

Rifampin is the cornerstone of antituberculosis therapy, but induction of hepatic cytochrome P4503A by rifampin markedly lowers HIV protease inhibitor plasma concentrations.

METHODS

This phase 1, open-label, one-arm study was designed to assess pharmacokinetic interactions and safety of atazanavir, ritonavir, and rifampin among 14 evaluable HIV-seronegative volunteers. The study included 3 sequential periods of study drug dosing, with plasma sampling for pharmacokinetic analyses to occur on the last day of each period. During period 1, participants received rifampin 600 mg every 24 hours for 8 days. During period 2, participants continued rifampin 600 mg every 24 hours, and added atazanavir 300 mg and ritonavir 100 mg every 12 hours, to continue for at least 11 days. During period 3, atazanavir was to be increased to 400 mg every 12 hours.

RESULTS

Upon adding atazanavir and ritonavir, the first 3 subjects developed vomiting and transaminase elevations resulting in study drug discontinuation. The study was therefore terminated.

CONCLUSIONS

Coadministration of rifampin with HIV protease inhibitors may not be a viable treatment option if rifampin administration precedes protease inhibitor initiation. Future studies, which explore concomitant HIV protease inhibitors with rifampin must carefully consider the sequence in which drugs are initiated.

[Pharmacology, pharmacokinetic features and interactions of atazanavir]

Atazanavir (ATV) is an HIV protease inhibitor (IP) with a high in vitro activity against HIV-1, that demonstrates a high additive activity in the presence of other antiretrovirals and a synergic activity with other PI. Oral absorption is greater than 68%, maximum concentration (C(max)) being reached approximately 2 to 3 h after its administration. Its absorption is dependent on gastric pH, its administration being recommended after meals. The pharmacokinetics (PK) of ATV are non-linear; that is to say, its plasma concentrations (C(p)) do not increase in proportion to the dose. ATV is approximately 86% bound to plasma proteins. Its entry into the cerebrospinal fluid, semen or genital secretions varies but is generally less than 10-20%. Its passage across the placenta, measured as the mean of the ratios between the C(p) in umbilical cord and maternal blood, is 0.13. ATV is metabolised by oxidation by cytochrome P450 enzymes, subsequently being eliminated by the bile duct in the free or glucuronide form (80%) and by the urine. ATV is a weak competitive inhibitor of CYP3A4 and a strong inhibitor of uridine diphosphate-glucuronosyltransferase 1A1, which is the cause of the frequent high plasma bilirubin after its administration and of its pharmacological interactions.

High incidence of adverse events in healthy volunteers receiving rifampicin and adjusted doses of lopinavir/ritonavir tablets

OBJECTIVE

Previous research in healthy volunteers has demonstrated that rifampicin and adjusted doses of lopinavir/ritonavir soft-gel capsules resulted in adequate exposure to lopinavir. Our objective was to study the combined use of rifampicin and the newly introduced lopinavir/ritonavir tablets.

METHODS

A total of 40 healthy volunteers were planned to start with 600 mg rifampicin once daily from days 1-5. From days 6-15, volunteers were randomized to receive lopinavir/ritonavir tablets dosed as either 600/150 or 800/200 mg twice daily, both in addition to 600 mg rifampicin once daily. A 12 h pharmacokinetic curve was planned on day 15. Safety assessments were conducted regularly throughout the study period.

RESULTS

Eleven volunteers started as the first group in this study. No major complaints occurred during day 1-5 (rifampicin only). After addition of lopinavir/ritonavir, eight volunteers suffered from both nausea and vomiting, one from nausea only, and one from vomiting only. On day 7, increases in aspartate aminotransferase/alanine aminotransferase (AST/ALT) levels were reported in all volunteers and on day 8, the study was prematurely terminated. The AST/ALT levels continued to rise and peaked (grade 2, n = 2; grade 3, n = 1; grade 4, n = 8) on days 9-10. All values returned to normal within 6 weeks.

CONCLUSIONS

The study showed a high incidence of adverse events when a higher than standard dose of the new lopinavir/ritonavir tablets was combined with rifampicin. In the future, this drug combination should not be given to healthy volunteers. Liver function should be carefully monitored when rifampicin and lopinavir/ritonavir are combined in patients.

Pharmacokinetic interaction between rifampicin and ritonavir-boosted atazanavir in HIV-infected patients

BACKGROUND

Tuberculosis (TB) is a common opportunistic infection among HIV-infected people, and rifampicin is an important drug for the treatment of TB. However, administration of rifampicin in combination with antiretroviral therapy, particularly protease inhibitors, is difficult because of drug-drug interactions.

METHODS

We have performed a prospective study in three HIV-infected patients with TB treated with a rifampicin-containing regimen (rifampicin 600 mg per day) and antiretroviral therapy including only nucleoside reverse transcriptase inhibitors (NRTIs) plus atazanavir 300 mg once a day (qd) and ritonavir 100 mg qd, to evaluate whether the inducing effect of rifampicin on the drug-metabolizing enzyme cytochrome P450 (CYP) 3A4 could be overcome by the inhibitory effect of ritonavir. A complete pharmacokinetic evaluation of the steady-state concentrations of atazanavir and ritonavir was performed.

RESULTS

In all three cases, more than 50% of the time the atazanavir level was below the minimum recommended trough plasma level (150 ng/mL according to current pharmacokinetic guidelines) to inhibit HIV wild-type replication.

CONCLUSION

These results strongly indicate that the administration of rifampicin with a combination of atazanavir 300 mg qd plus ritonavir 100 mg qd must be avoided because subtherapeutic concentrations of atazanavir are produced.