Penetration of didanosine in semen of HIV-1-infected men

Objectives: The disposition of antiretroviral agents into genital tissue and fluids is one of the factors implicated in the control of viral replication within the male genital tract and should be an objective of highly active antiretroviral therapy. We have investigated didanosine penetration in seminal plasma of 16 HIV-infected patients. Patients and methods: A total of 16 patients on didanosine (200 mg every 12 h or 400 mg once daily) participated in the pharmacokinetic study. After the didanosine morning dose, peripheral blood plasma and semen plasma were collected within the intervals 0-4, 4-8 and 8-12 h in the twice-daily regimen and 0-4, 4-12 and 12-24 h in the once-daily regimen. Results: Within each sampling time interval didanosine concentrations in seminal plasma were higher than in blood. The interquartile range of concentrations in seminal plasma was 292-1217 ng/mL, compared with 50-150 ng/mL in blood plasma. Didanosine could be detected in 14 of the 16 semen samples analysed and in 8 of the 16 blood samples. Conclusions: We have demonstrated that didanosine penetrates into the seminal plasma in higher concentrations than in blood plasma.