Study to Determine Interaction Between the Use of Feminizing Hormone Therapy and Antiretroviral Agents Concomitantly Among Transgender Women

Inclusion Criteria: 1. Thai nationality 2. Age 18-40 years old 3. Male-to-female transgender individual 4. PrEP/ART naïve 5. Body mass index 18.5-25 kg/m2 6. Calculated creatinine clearance (CrCl) ≥60 mL/min, as estimated by the Cockcroft- Gault equation 7. Alanine aminotransferase (ALT) ≤2.5 x ULN 8. Have signed the informed consent form Exclusion Criteria: 1. Known history of allergy to hormonal or ARV component to be used in the study 2. Male-to-female transgender who underwent orchiectomy 3. Any of the following in HIV-infected participants * CD4 \< 350 cells/mm3 * History of psychiatric disorder that may be worsening by taking EFV 4. Previous use of injectable GAHT in the past 6 months 5. Current use of any of the following medication: * Anticonvulsant: Phenytoin, carbamazepine or phenobarbitol * Ergot-containing agents: dihydroergotamine, ergotamine or other ergot derivatives * Sedatives: Midazolam or triazolam * Herbs: Gingko biloba, St John's wort or milk thistle * Anti-infective agents: Erythromycin, clarithromycin, ketoconazole, itraconazole, rifampicin or rifabutin 6. Alcohol or drug use that, in the opinion of the investigator, would interfere with completion of study procedures