HIV Post Exposure Prophylaxis

Introduction

Post-exposure prophylaxis (PEP) refers to the use of antiretroviral (ARV) medication to prevent HIV infection in an HIV-negative person who has had a potential exposure to the virus. It is a critical secondary prevention strategy.

• Definition: A short-term antiretroviral treatment initiated immediately after a specific high-risk exposure to HIV to prevent the virus from becoming established in the host.
• Scenarios for Use:
  • Occupational Exposure: Healthcare workers exposed via percutaneous injury (needlestick) or contact with mucous membranes/non-intact skin with potentially infectious body fluids.
  • Non-Occupational Exposure (nPEP):
    • Sexual Assault: A critical component of management for survivors of sexual assault.
    • Consensual Sexual Contact: Unprotected sexual intercourse with a partner of known or unknown HIV status.
    • Injection Drug Use: Sharing of needles or equipment.
    • Other: Human bites (if blood is involved) or accidents involving blood exposure.

Timing and Initiation

The efficacy of PEP is time-dependent. Animal studies and human observational data indicate that earlier initiation results in better outcomes.

• Golden Window: PEP should be initiated as soon as possible, ideally within 1–2 hours of exposure.
• Maximum Limit: Most guidelines recommend initiating PEP no later than 72 hours after exposure.
• Late Presentation: If a patient presents >72 hours after exposure, PEP is generally not recommended as it is unlikely to be effective. However, this visit should be used for counseling, baseline testing, and referral for care if infection occurs.

Baseline Assessment and Testing

Before starting PEP, a risk assessment and baseline laboratory evaluation are necessary. However, the first dose of PEP should not be delayed while waiting for laboratory results.

Risk Assessment

• Source Evaluation: If possible, determine the HIV status of the source. If the source is known to be HIV-positive, information on their viral load, antiretroviral treatment history, and drug resistance patterns helps tailor the PEP regimen.
• Exposure Type: Assess the severity of exposure (e.g., large-bore hollow needle, deep injury, visible blood, mucosal contact).

Laboratory Evaluation

• HIV Testing: Perform a 4th generation HIV antigen/antibody test (ELISA) to confirm the exposed person is HIV-negative at baseline.
  • PEP is not indicated if the person is already HIV-positive.
• Other Blood-Borne Viruses:
  • Hepatitis B (HBV): Test for HBsAg and HBsAb. If the patient has completed a vaccine series and is immune, testing may not be needed.
  • Hepatitis C (HCV): Test for HCV antibody.
• General Health:
  • Renal Function: Serum creatinine (important for Tenofovir dosage).
  • Liver Function: Alanine aminotransferase (ALT).
• Sexual Exposure Specifics: For sexual exposures, test for other sexually transmitted infections (STIs) such as Syphilis, Gonorrhea, and Chlamydia.

Recommended PEP Regimens

Current guidelines recommend a three-drug regimen for all significant risk exposures. The duration of treatment is 28 days.

The selection of drugs depends on the age and weight of the child or adolescent.

1. Adolescents (≥12 years) and Adults

• Preferred Backbone: Tenofovir Disoproxil Fumarate (TDF) + Emtricitabine (FTC).
• Third Agent:
  • Dolutegravir (DTG): An integrase inhibitor, preferred for its high barrier to resistance and once-daily dosing.
  • Raltegravir (RAL): An alternative integrase inhibitor (requires twice-daily dosing).
• Note: This aligns with adult guidelines and offers a convenient once-daily option if Dolutegravir is used.

2. Children 2 to <12 years

• Preferred Backbone: Tenofovir Disoproxil Fumarate (TDF) + Emtricitabine (FTC).
• Third Agent: Raltegravir (RAL).
• Rationale: TDF is generally approved for use in children aged 2 years and older (specifically approved for Hep B in children ≥12 years or >35kg, but used in HIV regimens for younger children based on weight bands).

3. Children <2 years

• Preferred Backbone: Zidovudine (AZT) + Lamivudine (3TC).
• Third Agent: Raltegravir (RAL) (approved for neonates ≥37 weeks gestation and ≥2 kg).
• Alternative: Lopinavir/ritonavir (LPV/r) can be used if Raltegravir is not available or suitable, though Raltegravir is preferred in newer guidance.

Drugs to Avoid in PEP

• Nevirapine (NVP): Contraindicated for PEP due to the risk of severe hepatotoxicity and severe skin rashes (Stevens-Johnson syndrome) in HIV-negative individuals with higher CD4 counts.
• Abacavir (ABC): Contraindicated for PEP because hypersensitivity reactions can be fatal and there is no time to screen for the HLA-B*5701 allele in an emergency setting.

Follow-up and Monitoring

Post-exposure care extends beyond the initial prescription.

Serological Follow-up

• Schedule: Repeat HIV testing at 4–6 weeks and 3 months post-exposure to document serostatus.
• Hepatitis C Co-exposure: If HCV transmission is a possibility (or confirmed in the source), HIV testing should be repeated at 6 months, as HCV co-infection can delay HIV seroconversion.

Adherence and Side Effects

• Adherence Counseling: Adherence to the full 28-day course is crucial for efficacy. Side effects (nausea, fatigue, headache) can lead to discontinuation.
• Monitoring: Monitor for toxicity based on the drugs used (e.g., anemia/neutropenia with Zidovudine, renal function with Tenofovir).

Prevention Education

• Use the PEP consultation as an opportunity to educate on risk reduction.
• For adolescents with ongoing high-risk behavior, discuss Pre-Exposure Prophylaxis (PrEP) as a future preventative measure after the PEP course is completed and HIV negative status is confirmed.