Pharmacokinetic and pharmacodynamic investigation of efavirenz in the semen and blood of human immunodeficiency virus type 1-infected men

Therapeutic concentrations of antiretroviral agents in seminal plasma (SP) may reduce virus burden and influence sexual transmission of human immunodeficiency virus (HIV) type 1. This study compared the pharmacokinetic, pharmacodynamic, and dose responses of efavirenz (EFV) in SP versus those in blood plasma (BP). A total of 431 BP samples and 157 SP samples were obtained over a period of 40 days, from 9 EFV-naive men (i.e., men about to receive EFV for the first time) and from 12 EFV-experienced men (i.e., men already receiving EFV as part of an antiretroviral regimen). Overall, median EFV exposure in SP was 3.4% (range, 2.0%-5.0%) of that in BP. However, all EFV concentrations in SP were greater than or equal to40-fold higher than the wild-type IC90 (IC90WT) for HIV-1. During the dosing interval, no single SP: BP EFV-concentration ratio was significantly predictive of the absolute measure of exposure in SP. By day 40, HIV-1 RNA in SP was undetectable in 8 (89%) of 9 EFV-naive men and remained undetectable in 10 (83%) of 12 EFV-experienced men. In SP, EFV reaches concentrations above the HIV-1 IC90WT throughout the dosing interval. EFV-containing regimens effectively suppress HIV-1 RNA in SP.