PrEP: Protection against HIV in a pill?

HIV (the human immunodeficiency virus) weakens the human immune system and destroys the important cells that fight disease and infection. A person can get HIV when bodily fluids — including blood, semen, pre-seminal fluid, rectal fluids, or vaginal fluids of a person with the virus — come in contact with a mucous membrane or damaged tissue. HIV can be transmitted through breast milk, or when a contaminated needle or syringe comes into direct contact with the bloodstream.

There is no cure for HIV, but with proper medical care the virus and its effects can be controlled. HIV transmission can be reduced by consistent use of condoms and clean needles. However, another way to protect against getting HIV is pre-exposure prophylaxis, or PrEP.

PrEP is a pill that can help prevent HIV

PrEP is a combination of two antiretroviral medications, tenofovir and emtricitabine, that, if taken every day, can now prevent HIV. The pill (Truvada) is FDA approved. Truvada works by blocking an enzyme so that HIV cannot reproduce and establish infection in the body.

The pill is taken by mouth with or without food. It is best if taken at the same time every day, as this helps establish a routine. Skipping days isn’t recommended. If you forget a dose, take it as soon as you remember. If it is almost time to take the next dose, skip the missed dose and continue the regular dosing schedule. Truvada takes full effect seven to 20 days after starting the medication. It can be discontinued whenever the protection it offers is not necessary (for example, if your risk for HIV or preferences change). Do talk to your doctor when stopping or starting any medication.

Who should consider PrEP?

The following circumstances mean that PrEP may be a good choice and worth a conversation with your doctor:

  • if you have had anal or vaginal sex with more than one partner and prefer to use condoms only sometimes or not at all
  • if you are a sexually active adult male who prefers male partners, whose HIV status may not be known
  • if you are in a relationship with an HIV-positive partner
  • if you have recently had a sexually transmitted infection in your anus or vagina
  • if you have had sex with people who inject drugs, or if you inject drugs yourself
  • if you are trying to conceive with a known HIV-positive partner
  • if you have used stimulants, poppers, cocaine, meth, ecstasy, or speed in the last six months.

What about condoms?

Condoms do provide protection against HIV. Unlike PrEP, they also protect against other sexually transmitted infections, and prevent pregnancy when used correctly and consistently.

Does PrEP have side effects?

Overall PrEP is very well tolerated. As with starting any medication, some people will experience side effects such as nausea, gas, or headache. In general, these side effects are mild and tend to improve with time if the medication is stopped. Kidney problems can occur infrequently, and so your doctor will monitor your kidney function with regular blood tests. Some people may experience a mild reduction in bone mineral density. The significance of this is not known, but it tends to stabilize or go back to normal over time.

PrEP does not interfere with most medications including suboxone, methadone, or oral contraceptives, and does not affect sexual performance. While this medication has been used extensively in pregnant and breastfeeding women who have HIV infection, the risk/benefit of using it for HIV prevention during pregnancy or breastfeeding needs to be individualized. Talk to your doctor if you are taking NSAIDs like ibuprofen or naproxen, or antivirals like valacyclovir or acyclovir.

What are the next steps if you think PrEP is right for you?

Make an appointment with your doctor and talk about why you think you would like to take this medication. Your doctor will run tests to check for HIV and other sexually transmitted infections as well as hepatitis A, B, and C, and check your kidney function before starting PrEP. Usually your provider will need to get prior authorization for the medication. Most insurances cover the cost. If your provider is uncomfortable prescribing this medication, ask to be referred to an HIV specialist in your area.

You will need to see your doctor initially after one month and then every three months, when HIV and sexually transmitted infection testing will be repeated. Your kidney health will be monitored via a blood test once within six months, and PrEP must be stopped if the kidneys are adversely affected.


Centers for Disease Control and Prevention, HIV Basics: About HIV.

Centers for Disease Control and Prevention, HIV Basics: PrEP.

World Health Organization, Guidance on oral pre-exposure prophylaxis (PrEP) for serodiscordant couples, men and transgender women who have sex with men at high risk of HIV.

US Public Health Service, Preexposure Prophylaxis for the Prevention of HIV Infection in the United States — 2014: A Clinical Practice Guideline (PDF).

Acknowledgements: Dr. Linda Shipton, MD, an internist and infectious disease specialist at Cambridge Health Alliance, for support during the preparation of this post.

The post PrEP: Protection against HIV in a pill? appeared first on Harvard Health Blog.

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