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Omeprazole Boosts Total Saquinavir Plasma Exposure

Several mechanisms may explain how omeprazole increases saquinavir absorption

WEDNESDAY, July 12 (HealthDay News) -- Total saquinavir plasma exposure is significantly increased in the presence of the proton-pump inhibitor omeprazole, according to a study published in the June 26 issue of AIDS.

Alan Winston, M.D., of St. Mary's Hospital in London, U.K., and colleagues conducted a 15-day study in which 18 healthy men and women received 1000/100 mg saquinavir/ritonavir twice daily and 40 mg daily of omeprazole with the morning dose on days 11 to 15.

The researchers found marked increases in all saquinavir pharmacokinetic parameters on day 15 and an 82 percent increase in total plasma exposure. They observed no short-term toxicities despite the increase in saquinavir exposure. They also found that there were no significant changes in ritonavir pharmacokinetics between days 10 and 15.

"The changes in the pharmacokinetic profile of saquinavir observed in this study are in keeping with a process of increased absorption rather than reduced clearance," the authors state. "Several potential mechanisms may explain this interaction. Solubility of saquinavir may be increased in a less acidic environment. Omeprazole has been shown to delay gastric emptying, which may increase protease inhibitor absorption. Furthermore, omeprazole may increase saquinavir absorption via an inhibitory effect on P-gp and other membrane-bound transporters."

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