PReP: Can A Pill A Day Prevent HIV? Daily vs On-Demand Dosing

December 15, 2022

A Powerful Prevention Pill

There have been significant strides in preventing and treating human immunodeficiency virus (HIV) in recent years. At the same time, over 1 million people are living with the disease in the United States. In bigger states like Texas, HIV currently affects over 90,000 people. If not for treatments like pre-exposure prophylaxis (PrEP), these figures would be much higher. The PrEP pill helps prevent HIV infection. Based on the user’s risk exposure, doctors will recommend either daily or on-demand PrEP dosing.

Prepare for PrEP

Pre-exposure prophylaxis is an antiretroviral drug designed to help specific groups at risk of HIV exposure. This drug encourages the body to produce more antibodies in preparation for coming into contact with the virus. The PrEP drug also fortifies healthy cells from the virus, as HIV tends to damage the immune system directly. Groups like men who have sex with men (MSM) and people with multiple sex partners should use PrEP when possible. People who inject drugs (PWID) are also at risk of contracting HIV and should consider PrEP use. In clinical trials, the medicine reduced the risk of HIV by more than 90%. For PWID, the risk falls to 74%. However, this drug does not guarantee absolute safety and should form part of a comprehensive safety strategy.

Taking PrEP daily

Pre-exposure prophylaxis is designed for daily use to confer maximum benefits, as the medicine only works when there is enough in the body. Doctors recommend a daily dosage for people with a continuous, significant risk of exposure to the HIV virus. The drug needs at least 7 days to be effective for anal sex and 20 days for vaginal sex. To get the best results, taking all doses on time is crucial.

Taking PrEP on demand

While PrEP was initially designed for daily use, there has also been success with on-demand use, also called event-based use. This method is typical reserved for people who are not regularly exposed to HIV but may need support if a high-risk situation is anticipated. On-demand prep usually follows a 2-1-1 schedule. The user should first take 2 pills 24 hours before the exposure. Another pill is taken 24 hours later, then the last pill 24 hours after the second dose. Rare side effects are possible when taking PrEP on demand. These include nausea, vomiting, diarrhea, headache, dizziness, and rashes. These symptoms usually disappear after a few days of taking the drug.

Preventing HIV

The PrEP drug is a great discovery that prevents HIV from infecting people. However, this medication does not cure HIV and is not 100% effective. Nonetheless, PrEP has significantly helped high-risk individuals from getting infected. There’s still a lot to be done to encourage more people to take PrEP. Although states like Texas have a higher uptake in PrEP use than average, people of color and underserved communities still need support. Along with PrEP, continued education about the disease and ongoing testing is crucial to prevent the spread of the disease.


“Since becoming a patient with HSNT, I feel seen, cared for, and more informed than I’ve ever been.”  –  Jordan Grahmann

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