Michele Turner

Simultaneous determination of nine antiretroviral compounds in human plasma using liquid chromatography.

A rapid, sensitive and specific high-performance liquid chromatographic (HPLC) method using UV detection was developed for the determination of nine antiretroviral compounds commonly found in plasma from patients receiving antiretroviral therapy. Analytes include indinavir, saquinavir, ritonavir, amprenavir, lopinavir, delavirdine, efavirenz, nelfinavir and its M8 metabolite. Analytes were isolated from plasma using tert.-butyl methyl ether and separation achieved via reversed-phase liquid chromatography on a C(8) column with a gradient mobile phase. Detection at 210 nm provided adequate sensitivity. Limit of quantification is 50 ng/ml and all analytes demonstrated linearity across 50-10000 ng/ml from a single 200-microliter plasma sample. Recovery from plasma was consistently high (>80%). This novel HPLC methodology allows us to simultaneously determine plasma concentrations of nine antiretrovirals, including lopinavir, in HIV-infected patients on a single HPLC system.

Effect of Seville Orange Juice and Grapefruit Juice on Indinavir Pharmacokinetics

Considerable interpatient variability in indinavir pharmacokinetics, possibly due in part to variable metabolism of the drug through intestinal cytochrome P450 (CYP) 3A4, may contribute to poor virologic response in certain individuals with HIV infection. The purpose of this study was to characterize the influence of intestinal CYP3A4 modulation with grapefruit juice and Seville orange juice on indinavir pharmacokinetics. In an open‐label, three‐period crossover study, 13 healthy volunteers received indinavir 800 mg every 8 hours for 1 day and a single 800 mg dose the next morning. The last two indinavir doses were taken with 8 ounces of Seville orange juice, single‐strength grapefruit juice, or water (control). Plasma samples were collected at time 0 (predose) and at 0.5, 1, 2, 3, 4, and 5 hours after the last indinavir dose. Concentration‐time data were analyzed using noncompartmental methods. Coadministration of Seville orange juice and indinavir resulted in a statistically significant increase in indinavir tmax (1.87 [1.65‐2.22] vs. 1.25 [1.03‐1.60] h; p < 0.05) without altering other pharmacokinetic parameter values. Grapefruit juice administration did not result in any changes in indinavir pharmacokinetics. Modulation of intestinal CYP3A4 by grapefruit juice and Seville orange juice did not alter the systemic availability of indinavir. The contribution of presystemic metabolism to indinavir interpatient variability appears to be small.

Detection of Nevirapine in plasma using thin-layer chromatography

BackgroundNevirapine (NVP) is widely prescribed in resource-poor settings to pregnant women for treatment and prevention of HIV infection. High rates of misreported adherence, however, have compelled clinicians to find alternative methods to ensure systemic drug exposure. This report describes a fast, inexpensive thin-layer chromatography (TLC) method to detect the presence of NVP in human plasma. MethodsHuman plasma was spiked with various concentrations of NVP. NVP was subsequently isolated using solid-phase extraction and visualized with TLC. Clinical samples with NVP concentrations predetermined by high-performance liquid chromatography were used to validate the TLC method. ResultsNVP was detected at concentrations as low as 60 ng/mL. The lower limit of detection was set at 100 ng/mL due to the clear spot definition at this concentration. The turnaround time for assay results averages several hours, and costs associated with the assay are considerably below standard drug quantitation techniques. ConclusionTLC provides a rapid, sensitive, and economical tool to qualitatively measure NVP in plasma. This method offers clinicians in resource-poor settings an alternative approach for measuring adherence, particularly in developing-world regions where NVP use is common and there is an immediate need to prevent mother-to-child HIV transmission.

Antiretroviral Drug Content in Products from Developing Countries

Generic and brand name antiretroviral drugs are becoming increasingly available in developing countries. We analyzed 6 antiretroviral medications from 4 international sources for drug content. The active ingredient in tested drug products was within 15% of the labeled amount (range, -12% to +15%) for drugs that were properly stored.