Many people with HIV are still wondering, though, about Viagra's effect on protease inhibitors since Viagra is metabolized in the liver by the same CYP3A4 enzyme that protease inhibitors are. According to Pfizer, there should be little effect on the protease inhibitor levels in the body, but on the other hand, the protease inhibitors may have a major effect on Viagra. Drugs that strongly inhibit CYP3A4, including ritonavir , will sharply retard Viagra's breakdown. Reproduced with permission. Inc. All rights reserved.
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