HIV post-exposure prophylaxis in Singapore is used in cases of a single known exposure to HIV, such as via an accidental needlestick in a healthcare worker.
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HIV, or the human immunodeficiency virus, is transmitted in bodily fluids. It attacks certain cells of the immune system, causing the patient to become vulnerable to many infections that would normally pose no problem for a healthy immune system. Transmission of HIV occurs via unprotected sex, or by exposure to infected blood. This can happen when people share needles during drug use or tattooing, when receiving a blood transfusion from an unscreened source, or when a healthcare worker suffers an accidental needlestick.
In some cases, people have a pattern of high-risk behavior, and cannot be sure exactly which interaction exposed them to HIV. However, in some cases, someone has a single known exposure to HIV. This is most common in the healthcare setting, when a worker experiences a needlestick injury contaminated with blood that is HIV-positive. However, there are other possible exposures that would qualify, including those related to unprotected sex (consensual or not) and injection drug use.
Can HIV Be Prevented?
The first step after a needlestick injury is usually to test the blood of the source patient for HIV, if the patient’s HIV status isn’t already known. Since it takes three months for the test to become positive, it’s possible that the source patient has been exposed to HIV recently, and is infectious but has not yet seroconverted (their blood test has not become positive). The chances of that will be evaluated to determine whether treatment is necessary.
After the exposure, the patient (the person who was exposed) has a chance of becoming HIV-positive. The risk from a single exposure is less than 1%; however, given the lifelong nature of the infection, most people who have an exposure are interested in reducing the risk of seroconversion (meaning that they go from being HIV-negative to HIV-positive).
Sometimes, antiretroviral medications are given to people who’ve had a known exposure to HIV. The medications are intended to prevent the virus from replicating, which can reduce the chances that the infection will become established within the body. This is called post-exposure prophylaxis, or PEP.
What is the Medication Regimen?
The first step when considering HIV PEP is to test the patient for HIV, to make sure that they weren’t already positive before the exposure occurred. After an exposure, it takes about three months for the HIV test to become positive, so this test won’t reveal whether an infection occurred from this exposure; it will reveal whether the person was previously infected.
Next, the prescriptions are started. HIV PEP must be started within 72 hours (3 days) of the exposure to have any effect, and is most effective when started sooner than that. Two or three medications are given, and they must be taken several times per day for four weeks. These medications do sometimes have side effects, with nausea being the most common; however, the benefit of preventing lifelong HIV infection is greater than the risks.
Can PEP Be Used More Than Once?
PEP is not appropriate for those who have ongoing exposures to HIV, such as those with a sexual partner who is HIV-positive. However, there is a method called pre-exposure prophylaxis, or PrEP, that can be used to decrease the risk of transmission in this case. This involves taking a low dose of HIV medication every day, to reduce the chances that any virus you encounter will be able to replicate and establish an infection in your body. The dose of medication used for PrEP is lower than that used for PEP.
References
HIV PEP at Shim Clinic, Singapore