What is the most suitable PrEP (Pre-Exposure Prophylaxis) regimen for a 28-year-old MSM (Men who have Sex with Men) with a history of seizures, seasonal allergies, and syphilis, who is interested in a long-acting injectable option and has normal kidney function?

Long-Acting Cabotegravir is the Best PrEP Option for This Patient

Long-acting cabotegravir every month × 2 doses, then every 2 months is the most appropriate PrEP option for this patient due to their preference for a long-acting injectable option, potential drug interaction concerns with their seizure medication, and excellent adherence history.

Rationale for Recommendation

Patient-Specific Considerations

1. Drug Interaction Concerns:

   • The patient is taking oxcarbazepine, an enzyme-inducing antiepileptic drug
   • Oxcarbazepine can potentially reduce the effectiveness of oral PrEP options containing tenofovir (both TDF and TAF formulations)
   • Long-acting cabotegravir avoids this potential interaction

2. Patient Preference:

   • The patient specifically expressed interest in a long-acting injectable option
   • Studies show high satisfaction rates with cabotegravir LA, with 75% of participants reporting satisfaction and 79% willing to continue therapy 1

3. Adherence Profile:

   • The patient reports excellent adherence to home medications
   • However, injectable cabotegravir eliminates daily pill burden, which may be beneficial long-term

Efficacy Considerations

Long-acting cabotegravir has demonstrated superior efficacy compared to oral PrEP options:

• Cabotegravir showed higher effectiveness than oral PrEP in randomized trials with a hazard ratio of 0.31 for HIV incidence among MSM and transgender women 2
• It is highly effective in populations with disproportionate HIV incidence 2
• The CDC and International Antiviral Society-USA panel recommend injectable cabotegravir as an effective alternative option with an evidence rating of AIa 3

Why Not Oral PrEP Options?

1. Emtricitabine/tenofovir disoproxil fumarate (F/TDF):

   • Potential drug interaction with oxcarbazepine
   • Less aligned with patient's preference for injectable option
   • Higher risk of renal adverse effects (patient has normal renal function now but monitoring would be required)

2. Emtricitabine/tenofovir alafenamide (F/TAF):

   • Also subject to potential drug interactions with oxcarbazepine
   • While F/TAF has a superior renal safety profile compared to F/TDF 4, the injectable option better aligns with patient preference

3. F/TAF 2-1-1 dosing:

   • On-demand dosing is less reliable with enzyme-inducing medications
   • Not the patient's stated preference

Implementation Plan

Initial Assessment and Administration

1. Pre-Initiation Testing:

   • Confirm HIV-negative status (already completed)
   • Verify no symptoms of acute HIV infection

2. Dosing Schedule:

   • Begin with oral lead-in of cabotegravir to assess tolerability
   • Administer first two monthly injections, then transition to every 2 months 5

3. Monitoring Schedule:

   • First follow-up at 1 month to assess tolerability
   • HIV testing before each injection
   • Quarterly STI screening is recommended given the patient's risk factors 3

Ongoing Management

1. STI Prevention:

   • Consider doxycycline post-exposure prophylaxis (doxyPEP) given the patient's recent history of syphilis 6
   • DoxyPEP can reduce incidence of syphilis by 73-87% and chlamydia by 70-88% 6

2. Adherence Support:

   • Schedule injection appointments in advance
   • Provide reminders for upcoming appointments
   • Have a plan for oral cabotegravir if an injection visit will be missed 5

Important Considerations and Potential Pitfalls

1. HIV Testing Challenges:

   • Diagnosis of HIV in the setting of long-acting cabotegravir can be challenging due to delayed detection of viremia, antigen, and antibodies (LEVI) 6
   • Use HIV RNA testing when available for monitoring

2. Missed Doses:

   • If a scheduled injection will be missed by more than 7 days, oral cabotegravir can be used for up to 2 months 5
   • Have a clear plan for transitioning back to the injection schedule

3. Injection Site Reactions:

   • While injection site pain is common, studies show it rarely leads to discontinuation (only 4% in one study) 1
   • Prepare the patient for potential injection site reactions but reassure that most find them tolerable

4. Long-term Monitoring:

   • Regular HIV testing before each injection
   • Quarterly STI screening
   • Ongoing assessment of risk behaviors and prevention needs

By choosing long-acting cabotegravir for this patient, you're providing an effective PrEP option that aligns with their preferences, avoids potential drug interactions, and offers high protection against HIV acquisition.