A 32-year-old HIV-negative gay man presents requesting pre-exposure prophylaxis (PrEP). He has a high-risk sexual partner and negative HIV test. Per WHO/CDC guidelines, which PrEP regimen is recommended as an alternative to daily TDF/FTC for on-demand PrEP (event-driven)?
- A Weekly TDF/FTC taken every Sunday
- B 2-1-1 regimen (TDF/FTC 2 tablets 2-24 hours before sex, 1 tablet 24 h after, 1 tablet 48 h after) ✓
- C Tenofovir alafenamide/emtricitabine (TAF/FTC) 2-1-1 regimen
- D Single-dose TDF/FTC immediately after sex (post-exposure)
Correct answer: B. 2-1-1 regimen (TDF/FTC 2 tablets 2-24 hours before sex, 1 tablet 24 h after, 1 tablet 48 h after)
Explanation
The 2-1-1 (or 'on-demand') TDF/FTC PrEP regimen — approved by WHO, EACS, and CDC — is recommended for men who have sex with men (MSM) at high risk: 2 tablets 2-24 hours before sex, 1 tablet 24 hours after the first dose, 1 tablet 48 hours after the first dose. The IPERGAY trial demonstrated non-inferiority to daily PrEP in this population. TAF/FTC 2-1-1 is not yet approved (TAF achieves lower vaginal tissue levels, making it inappropriate for women on on-demand regimens). Single-dose post-exposure is not PrEP. Weekly fixed-day dosing is not an approved regimen.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.