From aidsmeds.com…

Truvada (emtricitabine/tenofovir) as pre-exposure prophylaxis (PrEP) against HIV takes an estimated seven days to reach full efficacy and may protect for nearly a week afterward, the National AIDS Treatment Advocacy Project (NATAP) reports. But those taking PrEP should not assume these are hard facts at this time. Presenting their findings at the 15th International Workshop on Clinical Pharmacology of HIV and Hepatitis Therapy in Washington, DC, researchers conducted an analysis of 11 men and 10 women who took daily Truvada as PrEP for 30 days and then, after stopping the drug, remained in an additional 30 days of follow-up.

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