Amanda H. Corbett

Antiretroviral drug exposure in the female genital tract: implications for oral pre- and post-exposure prophylaxis

Objectives:To describe first dose and steady state antiretroviral drug exposure in the female genital tract. Design:Non-blinded, single center, open-label pharmacokinetic study in HIV-infected women. Method:Twenty-seven women initiating combination antiretroviral therapy underwent comprehensive blood plasma and cervicovaginal fluid sampling for drug concentrations during the first dose of antiretroviral therapy and at steady-state. Drug concentrations were measured by validated HPLC/UV or HPLC-MS/MS methods. Pharmacokinetic parameters were estimated for 11 drugs by non-compartmental analysis. Descriptive statistics and 95% confidence intervals were generated using Intercooled STATA Release 8.0 (Stata Corporation, College Station, Texas, USA). Results:For all antiretroviral drugs, genital tract concentrations were detected rapidly after the first dose. Drugs were stratified according to the genital tract concentrations achieved relative to blood plasma. Median rank order of highest to lowest genital tract concentrations relative to blood plasma at steady state were: lamivudine (concentrations achieved were 411% greater than blood plasma), emtricitabine (395%), zidovudine (235%) tenofovir (75%), ritonavir (26%), didanosine (21%), atazanavir (18%), lopinavir (8%), abacavir (8%), stavudine (5%), and efavirenz (0.4%). Conclusions:This is the first study to comprehensively evaluate antiretroviral drug exposure in the female genital tract. These findings support the use of lamivudine, zidovudine, tenofovir and emtricitabine as excellent pre-exposure/post-exposure prophylaxis (PrEP/PEP) candidates. Atazanavir and lopinavir might be useful agents for these applications due to favorable therapeutic indices, despite lower genital tract concentrations. Agents such as stavudine, abacavir, and efavirenz that achieve genital tract exposures less than 10% of blood plasma are less attractive PrEP/PEP candidates.

Kaletra (Lopinavir/Ritonavir)

OBJECTIVE: To review the pharmacology, virology, pharmacokinetics, efficacy, safety, and clinical use of lopinavir/ritonavir (Kaletra, Abbott Laboratories). DATA SOURCES: English-language MEDLINE and AIDSline searches were performed (1966–July 2001) using lopinavir, ABT-378, and Kaletra as key words. Abstracts from infectious diseases and HIV scientific meetings were identified. Abbott Laboratories provided additional published and unpublished information. DATA EXTRACTION: All publications, meeting abstracts, and unpublished information were reviewed and relevant items included. In vitro and preclinical studies were included as well as Phase II and III clinical trials. DATA SYNTHESIS: Lopinavir/ritonavir is a fixed-dose protease inhibitor (PI) combination used for the treatment of HIV-1 infection. Lopinavir, the active component of this combination, is extensively metabolized by CYP3A4 and produces low systemic concentrations when used alone. Ritonavir potently inhibits CYP3A4 and is used to enhance the systemic exposure of lopinavir. This combination results in lopinavir concentrations that greatly exceed those necessary in vitro to inhibit both wild-type and PI-resistant HIV isolates. In clinical trials with antiretroviral naïve and experienced patients, lopinavir/ritonavir was effective at suppressing HIV-RNA and increasing CD4+ T cell counts. Compared with other PIs, lopinavir/ritonavir may have advantages in the areas of pharmacokinetics, efficacy, and resistance. Toxicity, drug interactions, and medication adherence are important considerations surrounding its clinical use. CONCLUSIONS: Lopinavir/ritonavir is an effective option for the treatment of HIV-1-infected individuals when used in combination with other antiretroviral agents. It may be used as a component of initial therapy or salvage therapy; future studies will better define its place in therapy.

Protease inhibitor and nonnucleoside reverse transcriptase inhibitor concentrations in the genital tract of HIV-1-infected women.

The pharmacokinetics of antiretrovirals (ARVs) in the female genital tract (FGT) are likely to influence vertical and sexual transmission of HIV, the development of viral resistance, and post-exposure prophylaxis regimens. This study is the first to compare ARV concentrations in direct aspirates of cervicovaginal fluid (CVF) and blood plasma (BP). This unique method provides direct assessment of concentrations without the confounding of cervicovaginal lavage dilution. Of 8 ARVs, CVF concentrations ranged from <10% to >100% of BP concentrations. These large differences in CVF penetration suggest that further research into ARV pharmacokinetics and drug efficacy in the FGT is necessary.

Pharmacokinetic comparison of generic and trade formulations of lamivudine, stavudine and nevirapine in HIV-infected Malawian adults

Background:The Malawian antiretroviral program uses generic Triomune (stavudine, lamivudine, and nevirapine). Objective:To determine the pharmacokinetics and bioequivalence of generic and trade formulations of stavudine, lamivudine, and nevirapine in HIV-infected Malawians. Methods:This randomized, open label, cross-over study comprised of six men and six women currently receiving Triomune-40 TM who were randomized to the generic or trade formulation of stavudine (40 mg twice daily), lamivudine (150 mg twice daily) and nevirapine (200 mg twice daily). After at least 21 days, the alternate formulation was administered. At the end of each period, six blood samples were collected over 8 h. Bioequivalence was achieved if the 90% confidence interval (CI) for the geometric mean ratio (GMR) of generic:trade formulations for maximum plasma concentration (Cmax) and the area under the concentration–time curve (AUC) was within 0.8–1.25. Results:Mean patient age, weight, and height were 38.4 years (SD, 7.7), 71.2 kg (SD, 7.0), and 164.8 cm (SD, 6.3), respectively. The GMR for stavudine, lamivudine, and nevirapine were 1.4 (90% CI, 1.2–1.7), 1.1 (90% CI, 0.8–1.6), and 0.9 (90% CI, 0.7–1.2), respectively, for Cmax; and 1.1 (90% CI, 1.0 1.2), 1.0 (90% CI, 0.7-1.3), and 0.9 (90% CI, 0.7–1.1), respectively, for AUC0-8h. Regardless of formulation, Malawians had higher nevirapine exposures compared with historical reports of Western HIV-infected patients. Conclusions:Although exposures were similar, Triomune did not meet the strict definition of bioequivalence for these drugs. Patients taking Triomune had notably higher stavudine Cmax values. Antiretroviral pharmacokinetics and bioequivalence of generic formulations should be evaluated in the populations in which they are being used.

Combined oral contraceptives and antiretroviral PK/PD in Malawian women: pharmacokinetics and pharmacodynamics of a combined oral contraceptive and a generic combined formulation antiretroviral in Malawi.

This letter to the editor addresses the concern regarding women who are HIV positive and interested in oral contraceptives. HIV positive women are typically advised to avoid using combined oral contraceptives which proves difficult because COC’s are the most widely circulated contraceptives in the world. Health care professionals must understand the pharmacokinetics and pharmacodynamics between COC pills and ART treatments. This is especially important in areas with high rates of HIV positive women or where rates exceed 10% HIV positive females within the HIV population. In these areas women should be informed of the most effective treatment for their unique condition.

Antiretroviral pharmacokinetics in mothers and breastfeeding infants from 6 to 24 weeks post-partum: results of the BAN Study.

BACKGROUND An intensive, prospective, open-label pharmacokinetic (PK) study in a subset of HIV-infected mothers and their uninfected infants enrolled in the Breastfeeding, Antiretroviral and Nutrition (BAN) Study was performed to describe drug exposure and antiviral response. METHODS Women using Combivir(®) (zidovudine [ZDV] + lamivudine [3TC]) +Aluvia(®) (lopinavir/ritonavir [LPV/RTV]) were enrolled. Breast milk (BM), mother plasma (MP) and infant plasma (IP) samples were obtained over 6 h after observed dosing at 6, 12 or 24 weeks post-partum for drug concentrations and HIV RNA. RESULTS A total of 30 mother/infant pairs (10 each at 6, 12 and 24 weeks post-partum) were enrolled. Relative to MP, BM concentrations of ZDV and 3TC were 35% and 21% higher, respectively, whereas LPV and RTV were 80% lower. Only 3TC was detected in IP with concentrations 96% and 98% lower than MP and BM, respectively. Concentrations in all matrices were similar at 6-24 weeks. The majority (98.3%) of BM concentrations were >HIV(wt) IC50, with one having detectable virus. There was no association between PK parameters and MP or BM HIV RNA. CONCLUSIONS ZDV and 3TC concentrated in BM whereas LPV and RTV did not, possibly due to protein binding and drug transporter affinity. Undetectable to low antiretroviral concentrations in IP suggest prevention of transmission while breastfeeding may be due to antiretroviral effects on systemic or BM HIV RNA in the mother. Low IP 3TC exposure may predispose an infected infant to HIV resistance, necessitating testing and treating infants early.

Exploration of CYP450 and drug transporter genotypes and correlations with nevirapine exposure in Malawians

AIM Genetic polymorphisms have the potential to influence drug metabolism and vary among ethnic groups. This study evaluated the correlation of genetic polymorphisms with nevirapine pharmacokinetics exposure in Malawians. MATERIALS & METHODS CYP450 2B6, 2D6, 3A4 and 3A5, ABCB1 and constitutive androstane receptor and pregnane X receptor, were analyzed for polymorphisms in 26 subjects. RESULTS Allele frequencies (variant) were: CYP2B6 514G>T (0.31) CYP2D6*4 (0.02); CYP2D6*17 (0.35); CYP3A4*1B (0.77); CYP3A5*3 (0.25); ABCB1 2677G>T (0.0), ABCB1 3435C>T (0.21), NR1I3 13711152T>C (0.02), NR1I2 44477T>C (0.10), NR1I2 63396C>T (0.33), NR1I2 6-bp indel (del: 0.17). CYP2B6 516G>T (non-wild-type/wild-type) correlated with nevirapine pharmacokinetic parameters; geometric mean ratios (95% CI): 1.75 (1.27-2.40) for area under the concentration time curve (AUC)(0-12 h), 1.58 (1.03-2.42) for C(0), and 0.53 (0.31-0.91) for clearance. In a multivariable model, nevirapine AUC increased by 1.5% per year of age (p < 0.0001), CYP2B6 516 T allele increased AUC by 92% (p < 0.0001), and CYP3A5*3 decreased AUC by 31% (p = 0.0027). CONCLUSION Allele frequencies were similar to other sub-Saharan African populations. The T allele for CYP2B6 516 was significantly associated with nevirapine exposure.

The pharmacokinetics, safety, and initial virologic response of a triple-protease inhibitor salvage regimen containing amprenavir, saquinavir, and ritonavir

Summary:The aim of this study was to quantify the change in saquinavir and amprenavir exposure when combined and used with low-dose ritonavir; to evaluate 24-week safety and immunologic and virologic response. It was a randomized, nonblinded, prospective study. There were 11 HIV-1–infected, antiretroviral-experienced, male and female subjects ≥18 years old, median HIV-1 RNA and CD4+ T-cell count of 4.86 log copies/mL and 106 cells/mm3, respectively. Subjects were randomly assigned to receive saquinavir 1000 mg/ritonavir 100 mg every 12 hours or amprenavir 600 mg/ritonavir 100 mg every 12 hours for 7 days. After 12-hour pharmacokinetic sampling, the third protease inhibitor (PI) was added, and pharmacokinetics sampling was repeated 14 days later. Subsequent PI dosage adjustments were based on real-time pharmacokinetic assessment. Saquinavir did not affect amprenavir or ritonavir pharmacokinetics. Amprenavir decreased area under the concentration-time curve (AUC0–12h) and C12h for saquinavir 82 and 61%, and 74 and 75% for ritonavir. An adjusted PI regimen of amprenavir 600 mg/saquinavir 1400 mg/ritonavir 200 mg every 12 hours returned saquinavir exposure to baseline. At 24 weeks, HIV RNA declined a median of 1.55 log copies/mL and CD4+ T-cell counts increased a median of 52 cells/mm3. Gastrointestinal events predominated and were mild to moderate. These data suggest that amprenavir/saquinavir/ritonavir may be a viable salvage regimen in heavily PI-experienced individuals. New formulations of amprenavir and saquinavir may simplify this regimen.

Implementation of targeted interventions to decrease antiretroviral-related errors in hospitalized patients

PURPOSE The implementation and effectiveness of targeted interventions aimed at decreasing the frequency of antiretroviral-related errors in hospitalized patients with human immunodeficiency virus (HIV) are described. SUMMARY A prospective investigation conducted at the University of North Carolina Hospitals revealed a high rate of antiretroviral-related errors occurring on admission to the hospital and throughout a patients hospital stay. The high frequency of errors emphasized the need for targeted interventions aimed at preventing these errors and quickly identifying and resolving errors that do occur. Several interventions aimed at decreasing this error rate were instituted, including the addition of computer alerts for incorrect doses and drug interactions to the pharmacy order-entry system, distribution of an educational pocket-sized card among the staff, addition of commercially available combination antiretroviral products to the hospital formulary, updates of the computerized prescriber-order-entry (CPOE) system to include common dosage defaults, involvement of the infectious diseases consultation service to evaluate prescribed regimens of newly admitted patients with HIV, and daily review of newly initiated anti-retroviral regimens by a clinical pharmacist trained in HIV care. A follow-up analysis was conducted after these interventions were implemented to evaluate their effectiveness. Of the 78 patients identified during the postintervention analysis, 12 (15%) had at least one error in their initial drug regimen versus 49 patients (72%) in the preintervention study (p < 0.001). CONCLUSION Antiretroviral medication error rates decreased after the implementation of targeted interventions that included distributing an educational pocket-sized card, adding alerts to the pharmacy order- entry system, incorporating default dosages into the CPOE system, and adding combination antiretrovirals to the formulary.

Plasma Bile Acid Concentrations in Patients with Human Immunodeficiency Virus Infection Receiving Protease Inhibitor Therapy: Possible Implications for Hepatotoxicity

Study Objectives. To evaluate whether patients with human immunodeficiency virus (HIV) infection who were receiving protease inhibitor therapy had altered bile acid concentrations compared with noninfected control subjects, and whether bile acid concentrations could predict the onset of hepatotoxicity caused by protease inhibitors.