What is PrEP?
PrEP stands for Pre-Exposure Prophylaxis, a daily oral regimen of 2 drugs Tenofovir and Emtricitabine; prescribed a single fixed-dose combination tablet to prevent HIV transmission. It is to be differentiated from PEP or Post exposure prophylaxis where the person takes a 3-drug regimen within 72 hours after a possible exposure to HIV for 28 days.
PrEP is an additional preventive tool for sexually active gay men who are at high risk of HIV acquisition; it is NOT meant to replace condoms, but to supplement them.
PrEP does not prevent other sexually transmitted infections viz. syphilis, gonorrhoea, infections with Chlamydia, herpes simplex, hepatitis B and C etc.
Is PrEP effective?
Strict medication adherence is critical to PrEP efficacy. In a study involving gay men (the iPREX study), PrEP was associated with an average 44% reduction in HIV acquisition. However, the protection can be up to 92% if medication was detectable in the blood of persons in the trial (compared to those with no detectable medication in the blood)
At current times, it is recommended that PrEP be taken on a daily basis.
What is the time line to achieving protection?
The time from initiation of medications to maximal protection again HIV is unknown.
Drug levels are seen at rectal tissues by 7 days and maximum intracellular drug levels are seen at 20 days of daily oral dosing .
What laboratory tests do I need to do before and after starting PrEP?
PrEP should be prescribed from a healthcare setting.
A baseline HIV test must be performed at least 3 months from the last high-risk sexual exposure. The test MUST be negative before starting PrEP. Subsequently HIV tests must be done every 3 months to exclude acute HIV infections.
Taking PrEP when you are newly infected with HIV is very dangerous. This is because you will be under-treated, this will lead to resistant HIV strains that will make future treatment more challenging.
Medications for PrEP can hurt the kidneys. Baseline tests for kidney function have to be assessed and monitored every 6 months.
Screening for other STIs is also recommended at regular intervals.
Baseline Hepatitis B screening is also recommended as Tenofovir has activity against the virus and the doctor will need to monitor liver function tests.
What is Acute HIV infection?
Many people develop this illness a few weeks after being infected with HIV. This is possible if there is suboptimal adherence to daily PrEP.
The most common symptoms are fever, malaise, sorethroat, diarrhoea and rash. You should report there to your doctor if you develop these symptoms. The usual HIV blood test will probably be negative at this time and a test to detect the HIV RNA in the blood will be necessary.
For how long should I continue PrEP and how do I stop it?
You should continue to take PrEP daily for as long as you are at risk. If the situation changes and you are no longer at risk, continue PrEP for one month from the last sexual exposure.
Where can I get additional information on PrEP?
More FAQs are available at