What is the medication regimen for Post-Exposure Prophylaxis (PEP)?

Post-Exposure Prophylaxis (PEP) Medication Regimen

The preferred medication regimen for HIV post-exposure prophylaxis (PEP) is a three-drug combination of tenofovir disoproxil fumarate (TDF) + emtricitabine (FTC) as the backbone, plus either lopinavir/ritonavir (LPV/r) or atazanavir/ritonavir (ATV/r) as the third drug, administered for a full 28-day course. 1

Recommended Regimens by Patient Population

For Adults and Adolescents:

1. Preferred backbone regimen:

   • Tenofovir disoproxil fumarate (TDF) + Emtricitabine (FTC) or Lamivudine (3TC) 1

2. Preferred third drug options:

   • Lopinavir/ritonavir (LPV/r) OR
   • Atazanavir/ritonavir (ATV/r) 1

3. Alternative third drug options (where available):

   • Raltegravir (RAL)
   • Darunavir/ritonavir (DRV/r)
   • Efavirenz (EFV) 1

For Children ≤10 years:

1. Preferred backbone regimen:

   • Zidovudine (ZDV) + Lamivudine (3TC) 1

2. Preferred third drug:

   • Lopinavir/ritonavir (LPV/r) 1

3. Alternative backbone options:

   • Abacavir (ABC) + Lamivudine (3TC) OR
   • Tenofovir disoproxil fumarate (TDF) + Emtricitabine (FTC) or Lamivudine (3TC) 1

Newer Single-Tablet Regimens

Recent evidence supports the use of single-tablet regimens which may improve adherence:

1. Elvitegravir/cobicistat/tenofovir disoproxil fumarate/emtricitabine (Stribild®):

   • Demonstrated 92% completion rate 2
   • Higher completion rates compared to more frequently dosed regimens (71% vs 57% with TDF/FTC+raltegravir) 3

2. Bictegravir/emtricitabine/tenofovir alafenamide (BIC/FTC/TAF):

   • Showed 90.4% completion rate with minimal side effects 4

3. Tenofovir disoproxil fumarate/emtricitabine/rilpivirine (TDF/FTC/RPV):

   • 86.1% completion rate 5

Duration and Administration

• Duration: Full 28-day course 1
• Prescription: Provide the complete 28-day course at initial assessment 1
• Timing: PEP should be initiated as soon as possible, ideally within 72 hours of exposure 1

Monitoring and Follow-up

1. Baseline testing:

   • HIV antibody testing
   • Complete blood count
   • Renal and hepatic function tests 6

2. Follow-up testing:

   • Repeat laboratory tests at 2 weeks after starting PEP
   • Monitor for drug toxicity throughout the PEP course
   • HIV antibody testing at 6 weeks, 3 months, and 6 months post-exposure 6

3. Adherence support:

   • Enhanced adherence counseling is recommended for all individuals on PEP 1
   • Consider antimotility and antiemetic agents to manage gastrointestinal side effects 1

Common Side Effects and Management

• Gastrointestinal: Nausea, vomiting, diarrhea (most common)
• Constitutional: Fatigue, headache
• Management: Most side effects are mild to moderate and can be managed with supportive care

Important Considerations

• Risk assessment: PEP is indicated for exposures that pose a significant risk of HIV transmission (blood, genital secretions, cerebrospinal fluid exposure) 1
• Not indicated for: Exposures to tears, non-blood-stained saliva, urine, and sweat 1
• Contraindications: Known HIV infection in the exposed person or confirmed HIV-negative status of the source 1

Pitfalls to Avoid

1. Delayed initiation: PEP should be started as soon as possible after exposure, ideally within hours
2. Incomplete course: Provide the full 28-day course at initial assessment to improve completion rates
3. Inadequate follow-up: Ensure proper monitoring for toxicity and HIV seroconversion
4. Ignoring drug interactions: Be aware of potential interactions with other medications

The evolution of PEP regimens has moved toward better-tolerated, simpler dosing schedules with single-tablet formulations showing improved adherence and completion rates compared to older, more complex regimens.