Dr Wong Chen Seong
Deputy Director (National HIV Programme), Consultant
MBBS, MRCP (UK)
Dr Choy Chiaw Yee
MBBS, MRCP (UK)
Level 1 National Centre for Infectious Diseases
16 Jalan Tan Tock Seng Singapore 308442
(+65) 6357 7000
Mondays to Fridays: 8:30 am to 5:30 pm
Saturdays: 8:00am to 12:00pm
Sundays and Public Holidays: Closed
Pre-Exposure Prophylaxis (PrEP)
PrEP is a risk-reduction treatment against HIV which involves the daily consumption of HIV preventive medication. PrEP will be prescribed to HIV-negative patients who are at high risk of acquiring HIV infection after a review by our doctors. In addition, patients on PrEP will be provided with comprehensive sexual health services such as screening for sexually transmitted infections (STIs), and safer sex counselling.
Currently, PrEP is a combination of two anti-viral medications Tenofovir and Emtricitabine (TDF & FTC). These drugs are approved by both U.S. Food and Drug Administration and Singapore's Health Sciences Authority, and are highly effective in reducing the chances of an HIV-negative person contracting HIV infection.
Who May Be Suitable for PrEP?
PrEP may be useful for someone who is HIV-negative and if the person:
- Has a partner with HIV who is not on suppressive antiretroviral therap
- Is at risk of getting HIV through vaginal/ anal sex with multiple partners without the consistent use of condoms in the last 6 months
- Have sexually transmitted infections in the last 6 months
- Is a drug user who shares equipment and needles with others to inject drugs
Is PrEP Effective After Exposure to HIV?
PrEP is meant to reduce risk before exposure and only suited for people with constant ongoing high risk of acquiring HIV infection. If you have never started PrEP and are recently exposed to HIV, you should consider Post-Exposure Prophylaxis (PEP) within 72 hours after exposure to potential HIV infection. Do discuss further with our doctor on PEP.
How to Take PrEP?
PrEP is very effective if taken daily. Studies have shown that daily dosing of co-formulated TDF/FTC can reduce the risk of getting HIV by about 99% from sex. This needs to be taken for 7 days before high levels of protection are achieved for both vaginal and rectal exposure to HIV.
PrEP does not protect against other STIs, responsible safe sex and use of barrier contraception should be practised.
Recommended in cis-gender men who have sex with men. A double dose (two tablets) of co-formulated TDF/FTC to be taken 2-24 hours before potential sexual exposure, to be followed by single doses 24 and 48 hours after the initial dose.
When potential exposure is sustained for more than a 24-hour period, 1 tablet per day should be taken until the last exposure followed by the 2 post exposure tablets.
Safety & Adverse Side Effects
PrEP does not cause any serious side effects. The common side effects include upset stomach and nausea but the symptoms are mild and improve over time. You should tell your doctor if these or other symptoms become severe or do not go away.
First Doctor Consultation
You can discuss with our experienced infectious diseases doctor on HIV and sexual health to decide whether PrEP is right for you. Regular follow up visits with the doctor are required when you are on PrEP. Blood tests for HIV, STIs and baseline renal and liver functions will be offered by the doctor during first consultation.
Counselling will also be carried out to ensure medication is taken as prescribed, assess for side effects to medication, as well as to obtain new prescription so that PrEP is not interrupted. Sexual health counselling will also be provided to educate on the ways to reduce the risk of acquiring HIV. HIV tests will also be done regularly at 3 to 6 month intervals.
PrEP does not protect one against other sexually transmitted infections. Condoms provide the most effective barrier to HIV and are also the best way of reducing one's chances of picking up or passing on other STIs.
Subsequent Visits and Reviews
HIV blood tests, and STD screening, will be done every 3 to 6 months, with additional treatment depending on patient-reported sexual risk behaviour. Other age-dependent test for serum creatinine will be offered every 6 to 12 months.
The need for continued PrEP will be assessed by the doctor and determined based on assessment of the patient's risk of HIV infection within the past 12 months.
HIV testing and other relevant tests will be carried out to determine the HIV status and medical conditions such as Hepatitis B status of the patient. Patient will also be counselled to reconsider reinitiation of PrEP if the risk of HIV infection should become present again.