Will bariatric surgery affect the effectiveness of daily emtricitabine (Emtriva)/tenofovir disoproxil fumarate (Viread) for Pre-Exposure Prophylaxis (PrEP) therapy?

Continue Current Daily PrEP Without Modification

The best approach is to continue the current daily emtricitabine/tenofovir disoproxil fumarate regimen without any dose adjustments before or after bariatric surgery, as there is no evidence that bariatric surgery affects PrEP efficacy, and all proposed modifications lack clinical justification. None of the answer choices (A-D) are supported by current guidelines or evidence.

Why No Changes Are Needed

Daily Dosing Should Continue Unchanged

• Daily tenofovir disoproxil fumarate/emtricitabine is the recommended oral PrEP regimen for all populations at risk, with proven efficacy when taken as prescribed 1.
• The standard dose is one tablet daily (tenofovir disoproxil fumarate 300 mg/emtricitabine 200 mg), and this should not be altered based on surgical procedures 1, 2.
• There is no evidence in the medical literature or guidelines suggesting that bariatric surgery affects the absorption, efficacy, or safety of oral PrEP medications 1.

Why Each Proposed Option Is Inappropriate

Option A (Decrease to every other day): This is contraindicated because:

• Daily dosing is required for optimal protection, particularly for individuals with vaginal or "front-hole" tissue, where tenofovir concentrates at 10-fold lower levels than in rectal tissue 1.
• Reducing frequency would compromise protective drug levels and increase HIV acquisition risk 1, 2.

Option B (Event-driven dosing): This is inappropriate because:

• The 2-1-1 (on-demand) oral dosing schedule is recommended only for cisgender men who have sex with men (MSM), not for transgender men 1.
• Event-driven PrEP has not been studied or validated in transgender men, and efficacy data exist only for MSM with receptive anal intercourse 1.

Option C (Double the dose): This lacks any clinical rationale because:

• Double dosing is only recommended on the first day of PrEP initiation for MSM to achieve rapid protective levels 1, 2.
• There is no indication for dose escalation before surgery, and doubling the dose chronically could increase toxicity risk without benefit 1.

Option D (Switch to cabotegravir): While this is a valid PrEP option, it is not indicated here because:

• Injectable cabotegravir every 8 weeks is recommended specifically for cisgender men and transgender women who have sex with men 1.
• The patient is a transgender male (assigned female at birth), and cabotegravir's efficacy in this population has not been established in clinical trials 1.
• Switching medications solely due to upcoming surgery is unnecessary and could disrupt established adherence patterns 1.

Appropriate Clinical Management

Pre-Surgery Considerations

• Ensure the patient maintains daily adherence to current PrEP regimen through the perioperative period 1, 2.
• Coordinate with the surgical team to continue oral medications on the day of surgery if possible, or resume as soon as oral intake is tolerated postoperatively 1.
• If NPO (nothing by mouth) status extends beyond 24-48 hours, discuss temporary interruption with infectious disease consultation, though this is rarely necessary for bariatric procedures 1.

Monitoring Recommendations

• Continue standard PrEP monitoring: HIV testing quarterly, creatinine clearance at first quarterly visit and annually thereafter, and STI screening quarterly 1, 2.
• At the 3-month post-surgery follow-up, assess medication adherence and ensure no absorption issues have developed (though this is not expected) 1.

Important Caveats

• Bariatric surgery does not alter the pharmacokinetics of tenofovir or emtricitabine in any documented way, as these medications have excellent bioavailability and are not significantly affected by changes in gastric anatomy 3.
• The patient's gender identity as a transgender male means he may have vaginal tissue requiring the full 7-day protective window after PrEP initiation or interruption, not the 2-day window applicable to rectal tissue in MSM 1.
• If the patient has concerns about medication absorption post-surgery, reassure him that nucleoside/nucleotide reverse transcriptase inhibitors like those in his PrEP regimen have favorable absorption characteristics that are minimally affected by gastrointestinal changes 3, 4.