Pharmacokinetics of saquinavir co-administered with cimetidine

The present study evaluated the effect of cimetidine, a histamine H-2 receptor antagonist able to inhibit cytochrome P450 metabolism, on the steady-state pharmacokinetics of saquinavir soft gel. Twelve healthy volunteers (eight males and four females) participated in an open-label, double-phase pharmacokinetic study. Volunteers took saquinavir soft gel 1200 mg three times a day for 13 days and then saquinavir soft gel 1200 mg twice a day with cimetidine 400 mg twice a day from day 14 to 26. The pharmacokinetics of saquinavir on days 13 and 26 were compared. All 12 volunteers completed the study. The association of cimetidine with saquinavir soft gel 1200 mg twice a day resulted in a significant increase in saquinavir AUC(0-24) (120%; P = 0.023) and C-max (179%; P = 0.019), whereas C-trough did not differ significantly (32% increase; P = 0.272). Increased exposure to saquinavir was observed in healthy volunteers after co-administration with cimetidine. The most significant increase involved C-max. Further pharmacokinetic studies in HIV-infected subjects are warranted to confirm the boosting effect of cimetidine and to investigate any impact that the increase in saquinavir C-max may have on intracellular accumulation of the drug.