NPEP Guidelines for Patients Taking Rifampin
For patients on rifampin requiring non-occupational post-exposure prophylaxis (NPEP) for HIV, a modified antiretroviral regimen is necessary due to significant drug interactions, with dolutegravir-based regimens (dolutegravir 50mg twice daily plus tenofovir/emtricitabine) being the preferred option.
Drug Interaction Concerns
Rifampin is a potent inducer of cytochrome P450 enzymes and significantly affects antiretroviral drug metabolism through several mechanisms:
- Induces CYP3A4, leading to accelerated metabolism of many antiretrovirals 1
- Reduces plasma concentrations of protease inhibitors by up to 90% 2, 3
- Affects drug transporters like P-glycoprotein 3
These interactions can lead to subtherapeutic antiretroviral levels and potential prophylaxis failure.
Recommended NPEP Regimen for Patients on Rifampin
Preferred Regimen:
- Dolutegravir 50mg twice daily (dose adjustment required with rifampin) 1
- Tenofovir disoproxil fumarate/emtricitabine (TDF/FTC) 300/200mg once daily
Alternative Options:
- Raltegravir 800mg twice daily (doubled dose) plus TDF/FTC 1
Contraindicated Antiretrovirals with Rifampin
The following should NOT be used for NPEP in patients taking rifampin:
- Protease inhibitors (including boosted regimens) - severe reduction in drug levels 2, 3
- Rilpivirine or etravirine - significant decrease in efficacy 1
- Elvitegravir - contraindicated with rifampin 1
- Nelfinavir - specifically contraindicated in guidelines 1
Monitoring and Follow-up
- Baseline testing: Perform HIV antibody testing before starting NPEP
- Follow-up testing: Schedule at 6 weeks, 3 months, and 6 months post-exposure 4
- Additional monitoring:
- Monitor for drug toxicity within 72 hours and at least every 2 weeks while on NPEP
- Perform additional HIV testing if any symptoms of acute retroviral syndrome develop
Duration of NPEP
- Standard 28-day course of antiretrovirals
- Complete follow-up testing even after completing NPEP course
Special Considerations
For Pregnant Women
- Avoid efavirenz-based regimens due to potential teratogenicity 1
- Dolutegravir with appropriate dose adjustment remains an option
For Sexual Assault Survivors
- Same drug interaction principles apply
- Ensure proper documentation and follow local reporting requirements 1
Important Cautions
- Rifampin's enzyme induction takes approximately 1 week to reach maximum effect and persists for about 2 weeks after discontinuation 3
- If rifampin cannot be temporarily discontinued, antiretroviral dosing must be adjusted as specified above
- Standard NPEP regimens without dose adjustments will likely be ineffective in patients taking rifampin
Remember that timely initiation of NPEP (within 72 hours, ideally within 24 hours) is critical for efficacy regardless of the specific regimen chosen.