When taken daily by HIV negative individuals, PrEP can prevent the transmission of HIV from sexual intercourse with HIV positive persons by up to 99 percent regardless of whether or not condoms are used. For this reason, PrEP is particularly popular among serodiscordant couples, or relationships where one person has HIV and the other does not. Condoms can also be very effective at preventing HIV transmission, but some people choose not to use condoms for a variety of reasons.
A person's risk for contracting HIV typically depends on many factors. For instance, someone's risk of contracting HIV during unprotected anal intercourse is ten times higher when they are the receptive partner, or the "bottom," than when they are the insertive partner, or the "top." Research on heterosexual couples suggests that HIV positive individuals who are on antiretroviral treatment and have an undetectable viral load are already 96 percent less likely to transmit the virus to their HIV negative partner during intercourse than an HIV positive person who is not on treatment. This data is likely applicable to same-sex couples as well.
That said, viral loads can fluctuate, and data for blood viral loads may not always reflect viral loads in semen or vaginal fluids. If a person with HIV contracts another sexually transmitted infection, such as chlamydia or gonorrhea, their HIV viral load may suddenly increase. For these reasons, taking PrEP is a good idea for HIV negative individuals who have unprotected sex with people living with HIV or with partners whose HIV status is unknown.
People on PrEP should still routinely get tested for HIV because they will require additional medications should they become infected. When a person gets tested for HIV, they usually receive an antibodies test. HIV antibodies do not develop until up to three months after infection, so a person who has been recently infected may actually test negative in the first few weeks or months. This is what health care professionals call the "window period." If you take PrEP consistently on a daily basis, then you should be confident that an antibodies test will be accurate; however, if you are inconsistent with your PrEP use and fear that you have had an exposure, you should get an RNA test, which checks for the virus itself and has a much smaller window period.
PrEP should be taken every day for effective HIV protection, but human nature dictates that everyone will eventually forget a dose every now and then. If you remember that you missed a dose a few hours after you normally take your pill, go ahead and take it as soon as possible; however, if more than 12 hours have passed, simply wait to pick up where you left off on your next scheduled dose, and try not to forget in the future. Do not double dose.
Remembering to take a pill everyday may seem like a challenge, but there are many things that everyone does on a daily basis, such as brushing their teeth, eating lunch or going to bed. Try incorporating PrEP into one of these daily routines. You can also set a daily alarm on your phone or download one of the many apps available that provide medication reminders. Investing in a pill box with compartments for each day of the week can also help you keep track of your regimen. Even with these tools, some people still struggle with daily adherence. If you are unable to commit to taking a pill every single day, PrEP may not be for you at this time.
You should strive to take PrEP at the same time every day, but people's schedules change, and it is ok to adjust your regular dosing time if the need arises. For instance, if you usually take your pill when you wake up and want to start taking it before you go to bed, it is safe to either skip your regular morning dose and start your nightly ritual or to take one pill in the morning and one in the evening before switching to an evening-only schedule. If you travel to a different time zone, it is ok to stick with your regular dosing schedule; there is no need to figure out the time difference. The important thing is that you try to maintain consistency on a day-to-day basis.
You can stop taking PrEP at any time without concern of withdrawal effects; however, it is recommended to keep taking PrEP for at least a month after your most recent suspected HIV exposure. If you are in a monogamous relationship and are considering discontinuing PrEP, you and your partner should get tested for HIV together to make sure you are both negative. Even if you and your partner have agreed to be monogamous, you may still want to continue taking PrEP because even well intentioned people make mistakes and are dishonest sometimes. You cannot control anyone else's behavior, but PrEP gives you control over your own health.
PrEP is perfectly safe to take if you've been drinking alcohol, and no interactions have been documented with other recreational drugs.
The decision to use PrEP is yours and your alone. Never feel obligated to tell anyone, including your sexual and romantic partners, that you are on PrEP. Talking openly about PrEP can be good for others to hear, but ultimately it is between you and your doctor.
The most common complaint associated with PrEP is nausea, but this symptom usually subsides after a few weeks of regular use. You can try changing the time you normally take your pill to help cope with nausea; for instance, some people find it easier to take on an empty stomach or right before they go to sleep. Talk to your doctor if nausea persists after a month of taking PrEP.
Many people living with HIV have been taking the drugs used in PrEP for years with no side effects. You should get regular check ups and blood analysis to make sure PrEP is not affecting your kidney functions, but PrEP is generally considered to be very safe, and all side effects go away after PrEP is discontinued.