Hiransuthikul A, et al. - Researchers sought to evaluate potential drug-drug interactions between feminizing hormone therapy (FHT) and antiretroviral therapy (ART) transgender women (TGW) via measuring intensive pharmacokinetic parameters (PK) of blood tenofovir (TFV), efavirenz (EFV), and estradiol (E2) among 20 newly-diagnosed HIV-positive TGW. At baseline, FHT (estradiol valerate 2 mg and cyproterone acetate 25 mg) were prescribed until week 5 and restarted at week 8. At week 3, initiation of ART (tenofovir disoproxil fumarate/emtricitabine/efavirenz 300/200/600 mg) was done. Measurement of intensive E2 PK was done at weeks 3 (without ART) and 5 (with ART), and measurement of intensive TFV and EFV PK was done at weeks 5 (with FHT) and 8 (without FHT). Outcomes revealed significantly lower E2 PK in the presence of TDF/FTC/EFV, and some lower TFV and EFV PK in the presence of FHT among HIV-positive TGW.