Written by:

PULSE Clinic

PULSE Clinic

Established in Bangkok, PULSE Clinic is a gay-owned private clinic whose mission is to promote and provide excellence in standards of care and education in sexual wellbeing, HIV and related infections, and to actively engage in the formulation of public health policy and research, with the aim of reducing HIV disease burden worldwide.


Share on facebook
Share on twitter
Share on whatsapp
Share on linkedin
Share on telegram


Many people don’t know that HIV has the ability to mutate and become resistant to drugs. How does this affect you if you’re taking PrEP or not? Let’s take a look.

Q: What is PrEP?

A: PrEP means Pre-Exposure Prophylaxis, and it’s the use of anti-HIV medication that keeps HIV negative people from becoming infected.

Q: What is wild-type HIV?

A: This is the HIV in its most natural state. It is a non-mutated strain of a virus.

Q: What is drug-resistant HIV?

A: This refers to HIV that has mutated and multiplied/reproduced itself in the presence of antiretroviral drugs that usually kill them (HIV treatment and PrEP).

Q: How does drug-resistant HIV happen?


– Transmission of drug-resistant HIV. Most HIV positive people are infected with wild-type HIV but around 10% are infected with drug-resistant HIV. Many HIV positive people now take HIV drugs for treatment. If someone’s HIV has developed resistance to one or more of these HIV drugs and has unprotected sex or shares needles with other who is not infected, it is possible that they can infect their partner with a drug-resistant HIV. 

– Before HIV treatment. Even if someone is infected with wild-type HIV, genetic changes still happen, even before treatment is started. This ends up creating a large mixture of virus in the body. Some of these variants contain the necessary mutations that can partially, or fully, resist an antiretroviral drug. 

 – During treatment. After combination HIV drug treatment is started, the amount of wild-type virus is dramatically reduced to undetectable level. If we keep the HIV suppressed, the mutation to drug-resistance won’t happen. However, if the amount of virus isn’t pushed down and kept at very low levels, HIV variants can continue replicating, acquiring additional mutations. And once the virus has accumulated enough mutations, a high level of resistance to the drugs being used can occur, causing viral load to increase and CD4 cells to drop.

– HIV treatment halted and poor treatment adherence. HIV treatment only work perfectly when taken exactly as prescribed. Abrupt discontinuation of treatment (such as skipping doses, not taking  medication correctly, not getting refilled because of COVID-19 or because of chemsex, or because you simply forgot the appointment or are stuck in country where HIV meds are not available) can cause the amount of an HIV drug to decrease in the bloodstream.

If the drug level becomes too low, HIV can reproduce more freely and accumulate additional mutations. There are a number of reasons why someone might struggle with treatment adherence, including side effects, chemsex, COVID-19, a hectic schedule, forgetfulness, poor schedule management. If you’ve been having difficulty adhering to your drug regimen, it’s nothing to be embarrassed about—be sure to tell your doctor so that they can offer you solutions.

– While taking PrEP. In the US, Truvada was approved by US Food and Drug Administration (FDA) in July 2012 to prevent people from HIV. But there is the possibility that PrEP could be started in people who are newly infected with HIV, but HIV tests that we use nowadays cannot detect such infections.

Q: Why is PrEP and drug resistance a concern?

A: We know that PrEP works very well to prevent HIV infection when taken correctly and consistently. We have proven that PrEP works well by checking your HIV status through testing. However, there are a lot of people who don’t want to get tested and start PrEP. Those who don’t get tested doesn’t mean they don’t have HIV. Maybe they just don’t know they have it. 

They may start PrEP before they know they are infected, or they can become infected with HIV while using PrEP. If this happens, the virus in their body could change, or mutate, and become resistant to these ARV drugs.  People who have HIV typically need to take 3 ARV drugs to stop the virus from making copies of itself (also called replicating). When drug resistance occurs, some ARVs are no longer able to stop HIV from multiplying and the person would need to start taking a different combination of ARV drugs and 10 times more expensive. Ultimately, this means that the PrEP user may have fewer choices of the ARV drugs that they can use for treatment when they become infected with drug resistant HIV.

Q: Why do some people not get tested before taking PrEP?

A: There can be many reasons, including ignorance, laziness or other concerns regarding their privacy and worries about being discriminated. People who buy PrEP from online pharmacies or from street pharmacies because it’s easier, faster, and cheaper may be putting themselves and their sexual partners at risk.

Q: I don’t want frequent doctor visits, can I buy PrEP from a pharmacy without getting tested?

A: If you don’t get tested and proceed with PrEP, later on when you find out you are HIV positive with drug resistant HIV, you’ll not be able to avoid frequent doctor visits as a HIV positive person. And you will have to do that for the rest of your life, if you don’t want your HIV infection to develop to AIDS.

Q: Will drug resistance become a bigger problem when PrEP is rolled out at larger scale?

A: Possibly. We do know that the risk of drug resistance was low in completed clinical trials where study participants were assigned to take a daily PrEP. But the risk of drug resistance in the “real world” may differ because: 
– In clinical trials, study participants received free HIV testing once a month, which allowed research clinicians to immediately stop PrEP use once infection was identified; in the real world, HIV testing may be done every three months, or different intervals, or not at all.
– We do not know how well each PrEP users take their PrEP; when PrEP is not taken consistently, risk of HIV infection is greater and more chance for drug resistant to develop.
– There is the possibility that PrEP could be started in people who are newly infected with HIV, but HIV tests that we use nowadays cannot detect such infections, so it is possible to miss a diagnosis even in such tight control settings.

Q: What can I do?

A: If you’re on PrEP, don’t put yourself at this risk. Do not have sex with people who are taking PrEP without getting tested. If they tell you they’re on PrEP, ask them when was the last time they get tested. They should have blood test results on email or a photo of their last test results. There are people who even fake their blood test results just to have unprotected sex. Trust us, a short course of heavenly fun is not worth the risk.