Post Exposure Prophylaxis Therapy for HIV

The impact of exposure to human immunodeficiency virus (HIV) depends on two main factors: (1) Nature of exposure and (2) The status of the source patient (the patient to whose blood or body fluids exposure has occurred). There is need to evaluate the source patient within 2 hours of exposure so that post exposure prophylaxis (PEP) could be started. The initiation of PEP should not be delayed more than 72 hours in any case. The baseline HIV testing should also be done for the exposed person before starting post exposure prophylaxis therapy. The post exposure prophylaxis refers to the comprehensive management given to the exposed person to minimize the risk of infection following potential exposure to blood-borne viruses (HIV, HBV and HCV). The risk assessment could only be evaluated through relevant laboratory investigations. Antiretroviral therapy should be started after consultation with the physician and follow up and supportive counseling should be provided to the exposed person at the surveillance centers.

The relative risk of HIV transmission after different routes of exposure has been established as under:

Exposure Route	HIV Transmission
Blood transfusion	90-95%
Sexual intercourse-Vaginal	1-10%
Sexual intercourse-anal	0.05-0.5%
Sexual intercourse-oral	0.005-0.01%
Perinatal	20-40%
Intravenous drug use	0.5-1%
Needle stick injury	0.5%
Mucous membrane splash to eyes	0.1%

The exposure to blood, semen, vaginal secretions, cerebrospinal fluid, synovial fluid, pleural fluid, pericardial fluid and amniotic fluid is considered risky and infectious. However, exposure to tears, sweat, urine, faeces and saliva is not considered infectious unless these secretions contain blood. The exposure is considered mild if the contact is with the eyes or mucous membranes or there is needle stick injury with small bore needle generally during vaccination or skin testing. The exposure is considered moderate if the mucous membranes or intact skin is exposed to large volume of body fluid or blood of the infected patient. A cut with surgical blade or needle stick injury with blood smeared needle. The exposure is considered severe if the accidental prick is with high bore (> 18G) needle contaminated with blood or a deep wound is caused with surgical knife smeared with blood. Transfusion of infected blood or packed cells.

The prescription of post exposure prophylaxis depends on the category of exposure. For mild exposure, basic regimen or 2-drug combination is generally prescribed depending on the status of the source of exposure. If the exposure source is HIV+ but asymptomatic, consider 2-drug PEP and if the source is HIV+ and clinically symptomatic, immediately start 2-drug PEP. In case of moderate exposure to HIV+ but asymptomatic source, start 2-drug PEP. If the source is found HIV+ and clinically symptomatic in case of moderate exposure, start expanded regimen which is 3-drug combination. In case of severe exposure to an HIV+ but asymptomatic or clinically symptomatic source, immediately start 3-drug combination. PEP regimens prescribed by health centers are: (1) 2-drug regimen: Zidovudine (AZT) + Lamivudine (3TC) or Stavudine (d4T) + Lamivudine (3TC). (2) 3-drug regimen: Zidovudine (AZT) + Stavudine (d4T) + Lamivudine (3TC). Expert opinion is must before starting PEP therapy.