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HIV PEP (Post-Exposure Prophylaxis/Prevention), Singapore (SG)

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Non-occupational Postexposure HIV Prophylaxis

Doctors who manage patients with sexually transmitted infections may be confronted with the scenario of a patient requesting for non-occupational post-exposure (NO-PEP) HIV prophylaxis in the clinic. In such a situation, the physician should assess the likelihood that HIV will be transmitted as a consequence of the exposure, and advise the patient about the risks and benefits of treatment. Appropriate counseling must be given, and if the decision is made to treat, follow up care for potential side effects of medication, repeat HIV testing and reinforcement of counseling messages must be done.

Introduction

Antiretroviral therapy (ART) offered as PEP has become the standard of care for healthcare workers who have had occupational exposure to HIV. A case-control study has demonstrated that PEP with zidovudine was associated with an 81% decrease in the odds of HIV transmission with a percutaneous exposure in the occupational setting.1 Although there is no data to show that ART is effective at preventing transmission from non-occupational exposures, the principles of managing patients with recent HIV exposure are similar whether the exposure occurs in an occupational or non-occupational setting.

HIV Exposure Risk Assessment

A detailed and careful history of the exposure event is the first step in evaluating a patient.

Table 1 shows the risk of HIV transmission following a single percutaneous occupational, sexual, or injection drug exposure.2 Patients should be told that these are estimates, and in reality, the odds of infection with a specific exposure are hard to estimate because the risk of HIV transmission is affected by many factors such as the viral load of the infected person, presence of other sexually transmitted diseases, the size of the inoculum, and so forth. Certain sexual practices (receptive anal intercourse) carry much higher risk than others (insertive oral sex).

Generally, exposures to saliva, urine, tears and sweat are not though to be infectious, and the risk of HIV transmission from splashes of contaminated fluids to mucosal surface or non-intact skin has not been accurately quantified, although it is likely to be low.

Exposure - Estimated Risk
Needle stick injury3 - 1/300
Receptive ASI4 - 1/100
Receptive VSI5 - 1/1000
Insertive VSI4 - 1/2000
Insertive ASI4 - 1/2500
Receptive fellatio with ejaculation4 - 1/2500
Sharing needles6 - 1/150
Table 1. Estimated risks of HIV transmission per type of exposure

ASI=anal sex, VSI=vaginal sex.

Determination of eligibility for post-exposure prophylaxis

Individuals are eligible for HIV PEP if:

exposure occurred within the past 72 hours; and
the potentially exposed individual is not infected or not known to be infected with HIV; and
mucous membrane or non-intact skin was significantly exposed to a potentially infectious body fluid; and
the source is HIV-infected or the HIV status is unknown.

Regimen

HIV PEP | Shim Clinic, Singapore offers a triple drug combination of Combivir® (zidovudine 300mg/lamivudine 150mg) 1 tablet twice a day AND Kaletra® (lopinavir 200mg/rtionavir 50mg) 2 tablets twice a day both for a total of 28 days. The cost to the patient is approximately SG$3,300/= (inclusive of medication, laboratory tests, and consultation)

Side Effects

The drugs used can all cause GIT side effects i.e. nausea, diarrhoea, anorexia
ZDV: most side effects are dose-related; major side effect is haemtaological - anemia, granulocytopenia; pigmentation of nails reported
3TC: well-tolerated; rash, hair loss, vasculitis, photophobia, paraesthesia
Kaletra: diarrhea, nausea, headache, asthenia, rash, insomnia

Baseline Tests and Follow Up

Baseline HIV test is performed.

Full blood count, liver and renal function tests; these will detect any pre-existing abnormality prior to treatment and can be repeated if necessary.

Patients should be seen after 2 and 4 weeks to assess compliance and possible side effects of medication, as well as to reinforce prevention messages.

Counseling Patients

It is important to counsel patients that:

There is no absolute proof that ART PEP decreases risk of HIV, although there is supportive evidence based on biologic plausibility, animal studies and in a single study on HCW
The treatment is not 100% effective, as there have been documented cases of seroconversion after occupational exposures despite PEP
Side effects will be encountered with medication
Most importantly, issues of safer sex and how to prevent future exposures must be addressed