Introduction And Timing

Post-exposure prophylaxis represents a critical secondary prevention strategy utilizing short-term antiretroviral medication to prevent viral establishment in an HIV-negative host following high-risk exposure.
Administration must occur within a golden window of 1 to 2 hours post-exposure.
The absolute maximum limit for initiation is 72 hours; presentation beyond this timeframe renders therapy ineffective and is not recommended.

Clinical Indications

Exposure Category	Specific Scenarios
Occupational Exposure	Healthcare workers experiencing percutaneous needlestick injuries or mucosal contact with potentially infectious body fluids.
Non-Occupational Exposure	Survivors of sexual assault, consensual unprotected sexual contact, sharing of intravenous drug equipment, and human bites involving blood exposure.

The first dose of prophylactic medication must never be delayed while awaiting laboratory results.

Evaluation Parameter	Key Actions And Investigations
Source Assessment	Determine HIV status, viral load, antiretroviral history, and established drug resistance patterns of the source individual.
Exposure Assessment	Evaluate injury severity, including hollow needle use, deep tissue injury, or presence of visible blood.
HIV Screening	Perform a 4th-generation HIV antigen/antibody ELISA to confirm the exposed patient is strictly HIV-negative at baseline.
Viral Co-Infections	Screen for Hepatitis B (HBsAg, HBsAb) and Hepatitis C (HCV antibodies).
Organ Function	Evaluate baseline renal function via serum creatinine (critical for Tenofovir dosing) and liver function via Alanine Aminotransferase.
Sexual Exposure	Conduct concurrent screening for sexually transmitted infections, including Syphilis, Gonorrhea, and Chlamydia.

Current therapeutic guidelines mandate a definitive three-drug antiretroviral regimen administered for a standard duration of 28 days.

Patient Age And Weight Group	Preferred Regimen Backbone	Preferred Third Agent
Adolescents ($\ge$ 12 Years) And Adults	Tenofovir Disoproxil Fumarate + Emtricitabine	Dolutegravir OR Raltegravir.
Children 2 To <12 Years	Tenofovir Disoproxil Fumarate + Emtricitabine	Raltegravir.
Children <2 Years	Zidovudine + Lamivudine	Raltegravir (Lopinavir/ritonavir serves as a viable alternative).

Nevirapine: Strictly contraindicated due to the high risk of precipitating severe hepatotoxicity and life-threatening Stevens-Johnson syndrome in HIV-negative hosts possessing higher CD4 counts.
Abacavir: Strictly contraindicated because fatal hypersensitivity reactions can occur, and emergency settings do not permit adequate time for mandatory HLA-B*5701 allele screening.

Monitoring Category	Protocol Guidelines
Serological Follow-Up	Repeat HIV testing precisely at 4 to 6 weeks and 3 months post-exposure to definitively document serostatus.
HCV Co-Exposure	If Hepatitis C transmission remains a possibility, extend HIV testing to 6 months, as concurrent HCV infection can significantly delay HIV seroconversion.
Toxicity Monitoring	Clinicians must monitor for specific drug toxicities, notably renal impairment secondary to Tenofovir and anemia or neutropenia secondary to Zidovudine.
Counseling	Mandate strict adherence counseling to ensure completion of the full 28-day course and discuss future Pre-Exposure Prophylaxis for adolescents demonstrating ongoing high-risk behaviors.