n the other presentation, Kevin Brown of the University of North Carolina presented findings of maraviroc concentration in the semen and rectal tissue of male volunteers after oral dosing.
The study used twelve HIV-negative male volunteers, who took an eight-day course of maraviroc dosed at the treatment level of 300mg twice daily.
Blood and semen drug levels were measured five times in twelve hours after a single dose on days one, seven and eight of the study, and also once on days three to six. Rectal biopsy specimens were collected on days one, seven and eight.
After a single dose, semen and blood plasma levels were initially the same but after six hours semen levels fell off more quickly. Trough levels in semen were 70% of blood levels on days 7/8, and the area under the curve (AUC – total drug exposure) in semen was 60% of that in blood. Levels seen after multiple dosing were similar.
Concentrations in rectal tissue were much higher than in blood, with a mean trough level 91 times higher than in blood and the AUC 28 times higher.
Dr Brown said that the rectal tissue levels appeared promising for the use of maraviroc as a rectal microbicide. Levels might be higher because maraviroc was partially eliminated in the faeces.