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Pre-exposure prophylaxis (PrEP) prevents HIV infection through the daily administration of anti-HIV drugs, such as Truvada combination tablets (a combination of emtricitabine (FTC) and tenofovir disoproxil fumarate (TDF)). However, since PrEP is not approved in Japan, generic drugs sold overseas are imported and used by individuals. Then, the present study investigated the pharmaceutical equivalence of two generic drugs of Truvada (Generic A and Generic B). Tablet properties were examined by X-ray diffraction and differential scanning calorimetry. The dissolution behaviors and membrane permeabilities of FTC and TDF were assessed by the dissolution test using the paddle method and a membrane permeation experiment using Caco-2 cell monolayers, respectively. The dissolution behaviors of FTC and TDF differed between Truvada and its generic drugs. Furthermore, the membrane permeation rates of FTC and TDF in Generic B were slower than those in Truvada, and the AUC of FTC in Generic B was significantly smaller than that in Truvada. Differences were observed in the dissolution behaviors and membrane permeabilities of FTC and TDF in generic drugs (particularly Generic B) from those in Truvada. Since there are concerns regarding the clinical implications of these results, further studies, including in vivo experiments, are needed to ensure the safety of generic drugs. [ABSTRACT FROM AUTHOR]