Factors affecting antiretroviral pharmacokinetics in HIV-infected women with virologic suppression on combination antiretroviral therapy: a cross-sectional study.

BACKGROUND: Although some studies show higher antiretroviral concentrations in women compared to men, data are limited. We conducted a cross-sectional study of HIV-positive women to determine if protease inhibitor (PI) and non-nucleoside reverse transcriptase inhibitor (NNRTI) C(min) and Cmax values were significantly different than historical general population (predominantly male) averages and to evaluate correlates of higher concentrations. METHODS: HIV-positive women with virologic suppression (viral load < 50copies/mL) on their first antiretroviral regimen were enrolled. Timed blood samples for C(min) and Cmax were drawn weekly for 3 weeks. The ratio of each individual's median C(min) and Cmax to the published population mean values for their PI or NNRTI was calculated and assessed using Wilcoxon sign-rank. Intra- and inter-patient variability of antiretroviral drug levels was assessed using coefficient of variation and intra-class correlation. Linear regression was used to identify correlates of the square root-transformed C(min) and Cmax ratios. RESULTS: Data from 82 women were analyzed. Their median age was 41 years (IQR=36-48) and duration of antiretrovirals was 20 months (IQR=9-45). Median antiretroviral C(min) and Cmax ratios were 1.21 (IQR=0.72-1.89, p=0.003) (highest ratios for nevirapine and lopinavir) and 0.82 (IQR=0.59-1.14, p=0.004), respectively. Nevirapine and efavirenz showed the least and unboosted atazanavir showed the most intra- and inter-patient variability. Higher CD4+ count correlated with higher C(min). No significant correlates for Cmax were found. CONCLUSIONS: Compared to historical control data, C(min) in the women enrolled was significantly higher whereas Cmax was significantly lower. Antiretroviral C(min) ratios were highly variable within and between participants. There were no clinically relevant correlates of drug concentrations. TRIAL REGISTRATION: NCT00433979.

Interactions between recreational drugs and antiretroviral agents.

OBJECTIVE: To summarize existing data regarding potential interactions between recreational drugs and drugs commonly used in the management of HIV-positive patients. DATA SOURCES: Information was obtained via a MEDLINE search (1966-August 2002) using the MeSH headings human immunodeficiency virus, drug interactions, cytochrome P450, medication names commonly prescribed for the management of HIV and related opportunistic infections, and names of commonly used recreational drugs. Abstracts of national and international conferences, review articles, textbooks, and references of all articles were also reviewed. STUDY SELECTION AND DATA EXTRACTION: Literature on pharmacokinetic interactions was considered for inclusion. Pertinent information was selected and summarized for discussion. In the absence of specific data, prediction of potential clinically significant interactions was based on pharmacokinetic and pharmacodynamic properties. RESULTS: All protease inhibitors (PIs) and nonnucleoside reverse transcriptase inhibitors are substrates and potent inhibitors or inducers of the cytochrome P450 system. Many classes of recreational drugs, including benzodiazepines, amphetamines, and opioids, are also metabolized by the liver and can potentially interact with antiretrovirals. Controlled interaction studies are often not available, but clinically significant interactions have been observed in a number of case reports. Overdoses secondary to interactions between the "rave" drugs methylenedioxymethamphetamine (MDMA) or gamma-hydroxybutyrate (GHB) and PIs have been reported. PIs, particularly ritonavir, may also inhibit metabolism of amphetamines, ketamine, lysergic acid diethylmide (LSD), and phencyclidine (PCP). Case series and pharmacokinetic studies suggest that nevirapine and efavirenz induce methadone metabolism, which may lead to symptoms of opiate withdrawal. A similar interaction may exist between methadone and the PIs ritonavir and nelfinavir, although the data are less consistent. Opiate metabolism can be inhibited or induced by concomitant PIs, and patients should be monitored for signs of toxicity and/or loss of analgesia. PIs should not be coadministered with midazolam and triazolam, since prolonged sedation may occur. CONCLUSIONS: Interactions between agents commonly prescribed for patients with HIV and recreational drugs can occur, and may be associated with serious clinical consequences. Clinicians should encourage open dialog with their patients on this topic, to avoid compromising antiretroviral efficacy and increasing the risk of drug toxicity.