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PrEP side effects

PrEP side effects

Updated on:
September 2, 2021

Usually, less than 10% of patients on experience any PrEP side effects. For those who do experience side effects, they tend to naturally go away within 1-2 weeks.

Side effects of PrEP

Short term side effects of PrEP

Some of the possible short-term side effects associated with PrEP (and PEP) include nausea, headaches, diarrhea, and vomiting. Trials show that these side effects impact between 1% and 10% of people on PrEP, and that they are generally mild and clear up on their own within a week or two. 

If you’re experiencing persistent symptoms after a couple of weeks, contact your healthcare provider.

Long term side effects of PrEP

In a small number of people, PrEP has resulted in a decrease in kidney, liver, and bone health. Fortunately, even in these cases, toxicity levels did not increase the patient’s risk of kidney or liver failure, or bone fracturing, and these changes were reversed after they stopped taking PrEP.

Regular lab testing every three months while on PrEP is incredibly important to make sure that PrEP is being tolerated well and not negatively impacting overall health.

HIV drug resistance

An individual can develop a resistance to the drugs in PrEP if they are HIV positive and unaware of their status. Developing a resistance to these drugs can limit a person’s future treatment options should they need them.

The risk of developing drug resistance has been shown to be low for those who were HIV negative prior to taking PrEP, but it is possible to develop resistance if the individual becomes HIV positive while on PrEP.

PrEP failure is very rare when taken as prescribed and regular testing is completed. In order to reduce the risk of developing resistance, regular HIV testing is necessary. In any case where a person using PrEP contracts HIV, PrEP needs to be discontinued as soon as possible.

PrEP and pregnancy

If HIV is contracted during pregnancy or while chestfeeding, there is a higher risk of transmitting HIV to the newborn. Fortunately, daily PrEP use is safe for both the parent and the baby while pregnant and chestfeeding.

Although there have not been any clinical trials specifically evaluating the efficacy and safety of PrEP during pregnancy, multiple studies in various cisgender populations have shown that the consistent, correct use of oral PrEP is highly effective in preventing HIV transmission. Thousands of pregnant cisgender women living with HIV have used the drugs (TDF and FTC) found in PrEP as part of their treatment, and research on pregnant cisgender women using TDF in the treatment of hepatitis B has found that the use of these medications is generally safe for these women and fetal development.

Studies have shown that there is no increased risk of birth defects, preterm delivery, or low birth weight associated with the use of TDF during pregnancy and lactation. However, limited evidence has found that infants born of mothers on TDF may have lower bone density.

It is important, despite data suggesting that PrEP is safe to take during pregnancy and chestfeeding, to attend regular clinical follow-ups to monitor the health of the mother and infant.

Interactions with other meds while on PrEP

Most of the commonly used medications and recreational drugs are not known to interact with PrEP, but there are some. Of the drugs and supplements that do interact with PrEP, Non-steroidal anti-inflammatory drugs (NSAID) are the most commonly used and should be avoided if possible. If pain-relief medication is needed, acetaminophen (brand name Tylenol) should be taken instead of ibuprofen (brand name Advil), acetylsalicylic acid (brand name Aspirin), or naproxen (brand name Aleve) if possible.

It is important to let your clinician know about any medications, supplements, or recreational drugs that you are taking to ensure that any potential drug interactions are considered before going on PrEP.

PrEP and HRT efficacy

PrEP can be used by people of all genders as PrEP components do not interact with hormones that some trans people choose to take; however, studies including trans people are few and sparse. 

There is some evidence that feminizing hormones taken by some trans women can lower the amount of PrEP drugs in the body by a small amount, although drug levels still remain high enough to protect against HIV. Because of this potential interaction it is recommended that trans women take PrEP daily rather than PrEP on-demand. Trans men who have frontal / vaginal sex should also take PrEP daily because daily dosing is needed to keep drug levels high in the front hole or vagina. There is currently no evidence showing how well PrEP works for people who have undergone gender affirming surgeries.

Studies on the effectiveness of PrEP in trans men are underway, but, due to ongoing transphobia and trans erasure, this population has been excluded from studies of PrEP effectiveness to date. When it comes to HIV risk, anyone who has sex with men who have sex with men (i.e. gay, bisexual, and queer men) may be at higher HIV risk.

There is no reason to believe that PrEP is not highly effective when taken consistently and correctly by trans men. As with anyone on PrEP, the drug must reach sufficient concentrations before it’s effective in preventing HIV. That does not necessarily rely on your gender, but rather on what kind of sex you’re having. The drugs in PrEP take about 21 days to reach maximum levels in vaginal tissues compared to 7 days for rectal tissues.

Reviewed by:
Dr. Caley Shukalek

Caley is passionate about evidence-based, patient-centred care, including telemedicine that can provide high quality care from wherever a patient may choose.

He helped create Alberta's PrEP guidelines and works as a specialist in General Internal Medicine with additional training in sexual health, including HIV and sexually transmitted infections.

He holds an Masters of Public Health from Johns Hopkins University, an MD from the University of Calgary and an MSc from the University of Alberta.