Nevirapine plasma concentrations are still detectable after more than 2 weeks in the majority of women receiving single-dose nevirapine - Implications for intervention studies

Background: Single-dose nevirapine is a highly cost-effective strategy to reduce perinatal HIV-1 transmission. Its major disadvantage is the selection of nevirapine resistance in 20% to 30% of women, probably attributable to the long elimination half-life of nevirapine. To develop intervention strategies, it is important to know the interpatient variability in nevirapine half-life in women receiving a single dose of nevirapine. Methods: HIV-negative, healthy, nonpregnant Dutch women were eligible for this study After administration of a single 200-mg dose of nevirapine to the subjects, blood was sampled for measurement of nevirapine twice a week for a total of 21 days. Nevirapine plasma levels were determined by a validated high-performance liquid chromatography method with a lower limit of quantification of 0.15 mg/L. The primary end point was the first sample with an undetectable nevirapine concentration. Results: Forty-four subjects participated. The median age, height, and body weight (interquartile range) were 26 (21-33) years, 1.72 (1.68-1.75) m, and 64 (59-75) kg, respectively. The median elimination half-life of nevirapine was 56.7 hours, with a range of 25.6 to 164 hours. The time to the first undetectable nevirapine plasma concentration was 10 days in 4 subjects, 14 days in 12 subjects, 17 days in 12 subjects, and 21 days in 9 subjects. In the remaining 7 subjects, nevirapine was still detectable on day 21, the last day of sampling. Time to an undetectable nevirapine plasma concentration was influenced by oral contraceptive use but not by age, height, body weight, body surface area, alcohol use, or smoking. Conclusions: Most women who received a single 200-mg nevirapme dose still had detectable plasma concentrations of nevirapine after more than 2 weeks. This information is valuable for designing intervention studies to prevent the development of nevirapine resistance.