What is the daily dose of Tenofovir alafenamide for HIV post-exposure prophylaxis?

Tenofovir Alafenamide Daily Dose for Post-Exposure Prophylaxis

For HIV post-exposure prophylaxis, tenofovir alafenamide 25 mg once daily (coformulated with emtricitabine 200 mg and bictegravir 50 mg as a single tablet) is the preferred regimen, taken for 28 days starting within 72 hours of exposure. 1

Preferred PEP Regimen with Tenofovir Alafenamide

• The CDC recommends bictegravir/emtricitabine/tenofovir alafenamide (BIC/FTC/TAF) 50/200/25 mg as a single tablet once daily for 28 days as the first-line post-exposure prophylaxis regimen. 1

• This single-tablet regimen simplifies adherence compared to multi-pill regimens and should be initiated ideally within 24 hours of exposure, but no later than 72 hours. 1

• Tenofovir alafenamide (TAF) is specifically preferred over the older tenofovir disoproxil fumarate (TDF) formulation due to superior renal and bone safety profiles. 1

Alternative TAF-Based Regimen

• An alternative multi-tablet regimen consists of dolutegravir 50 mg once daily PLUS emtricitabine/tenofovir alafenamide 200/25 mg once daily for 28 days. 1

• If tenofovir alafenamide is unavailable, tenofovir disoproxil fumarate 300 mg can be substituted, though TAF remains preferred. 1

• Lamivudine 300 mg can substitute for emtricitabine if needed. 1

Critical Implementation Details

• Initiate PEP as soon as possible—ideally within 24 hours and absolutely within 72 hours maximum, as efficacy decreases significantly with delayed initiation. 1

• Do not delay the first dose while awaiting laboratory results or source patient HIV testing. 1

• Complete the full 28-day course regardless of which regimen is used, as incomplete adherence significantly reduces effectiveness. 1

• If the source patient is confirmed HIV-negative during the 28-day course, PEP can be stopped early. 1

Renal Function Considerations

• For patients with impaired renal function, tenofovir alafenamide (TAF) is strongly preferred over tenofovir disoproxil fumarate (TDF) due to improved renal safety. 1

• Assess baseline renal function before initiating any tenofovir-based regimen. 1

• TAF demonstrates approximately 20-fold lower plasma tenofovir concentrations compared to TDF, resulting in reduced renal toxicity risk. 2

Monitoring Requirements

• Perform rapid or laboratory-based HIV antigen/antibody combination test at the initial visit. 1

• Add HIV nucleic acid test (NAT) if the patient received long-acting injectable PrEP in the past 12 months. 1

• Evaluate within 72 hours after starting PEP and monitor for drug toxicity for at least 2 weeks. 1

• Follow-up HIV testing at 4-6 weeks (HIV Ag/Ab test plus HIV NAT) and at 12 weeks (laboratory-based HIV Ag/Ab combination immunoassay and HIV NAT). 1

Evidence Supporting TAF for PEP

• BIC/FTC/TAF demonstrated excellent safety and tolerability in a prospective PEP study, with only 15.4% experiencing nausea/vomiting and 90.4% completing the full regimen—higher than historical PEP regimens. 3

• TAF achieves 7-fold higher tenofovir-diphosphate concentrations in peripheral blood mononuclear cells and approximately 6-fold higher concentrations in vaginal tissue compared to TDF, supporting its efficacy. 2

• In long-term studies, TAF maintained superior bone mineral density and renal safety biomarkers compared to TDF over 96 weeks. 4

Common Pitfalls to Avoid

• Never prescribe only two NRTIs (like tenofovir/emtricitabine alone) for PEP—this provides inadequate protection and requires a third drug, specifically an integrase inhibitor. 1

• Never delay initiation beyond 72 hours, as effectiveness drops precipitously with time. 1

• Never use salvage therapy agents (fostemsavir, ibalizumab) for PEP—these are reserved for treatment-experienced patients with documented resistance. 1

• Assess for potential drug interactions with concurrent medications before prescribing, particularly with integrase inhibitors. 1

• Consider different regimens if the patient has a history of antiretroviral exposure that might suggest resistance. 1

Transition to PrEP After PEP Completion

• Consider immediate transition from PEP to PrEP for persons with anticipated repeat or ongoing HIV exposures. 1

• Perform HIV testing at completion of the 28-day PEP course before transitioning to PrEP. 1

• For PrEP in men who have sex with men with or at risk for kidney dysfunction, osteopenia, or osteoporosis, daily tenofovir alafenamide/emtricitabine is recommended. 5