Is Kositaf (Tenofovir/Emtricitabine) effective for Post-Exposure Prophylaxis (PEP)?

Kositaf (Tenofovir/Emtricitabine) for Post-Exposure Prophylaxis

Kositaf (tenofovir/emtricitabine) is effective as part of a complete PEP regimen, but it is NOT sufficient as monotherapy—it must be combined with an integrase strand transfer inhibitor (INSTI) such as dolutegravir or bictegravir to provide adequate protection against HIV transmission. 1

Complete PEP Regimen Requirements

The CDC's 2025 guidelines are unequivocal that PEP requires three antiretroviral drugs, not just two nucleoside reverse transcriptase inhibitors (NRTIs) alone 1:

Preferred Regimens for Adults and Adolescents ≥12 years:

Option 1 (Single-Tablet):

• Bictegravir/emtricitabine/tenofovir alafenamide (BIC/FTC/TAF) once daily 1, 2
• This achieves 90-96% completion rates and has superior tolerability 3

Option 2 (Multi-Tablet):

• Dolutegravir PLUS (tenofovir alafenamide OR tenofovir disoproxil fumarate) PLUS (emtricitabine OR lamivudine) 1, 4
• Kositaf would provide the NRTI backbone in this regimen, but dolutegravir is essential 1

Why Kositaf Alone Is Insufficient

• Two-drug NRTI regimens (like tenofovir/emtricitabine alone) were used in earlier PEP protocols but are no longer recommended as monotherapy 5
• Three-drug therapy is now favored for all potential HIV exposures to maximize protection, particularly if the source person may be taking antiretrovirals 5
• The integrase inhibitor component provides critical additional antiviral activity that significantly improves efficacy 6, 5

Critical Implementation Details

Timing:

• Initiate PEP as soon as possible, ideally within 1-2 hours after exposure 7, 2
• Can be started up to 72 hours post-exposure, but effectiveness decreases with delay 7, 4

Duration:

• Complete the full 28-day course 7, 4
• Do not mistake PEP for a single-dose intervention 2

Monitoring Schedule:

• Baseline HIV testing (rapid or laboratory-based antigen/antibody combination test) before starting 7, 4
• Follow-up HIV testing at 4-6 weeks and final testing at 12 weeks post-exposure 7, 4
• Baseline and follow-up renal and hepatic function tests 7

Formulation Considerations

If using Kositaf specifically (which contains tenofovir disoproxil fumarate/emtricitabine):

• Tenofovir alafenamide (TAF) is preferred over tenofovir disoproxil fumarate (TDF) for patients with impaired renal function 4
• TDF-containing regimens like Kositaf have higher completion rates (72-87.5%) compared to older zidovudine-based regimens (42.1%) 8
• Common side effects include diarrhea or abdominal discomfort, but these are generally mild and self-limited 8

Common Pitfalls to Avoid

• Never prescribe tenofovir/emtricitabine alone for PEP—this provides inadequate protection 1
• Check for drug interactions, particularly with medications containing polyvalent cations 2
• Assess for potential interactions with concurrent medications before prescribing 4
• Stop PEP if the source person is confirmed HIV-negative during the 28-day course 7, 2

Transition to PrEP

For individuals with ongoing HIV exposure risk after completing the 28-day PEP course:

• Consider transitioning to pre-exposure prophylaxis (PrEP) 7, 4
• Perform HIV testing at completion of PEP before starting PrEP 4