Pre-exposure prophylaxis or PrEP is a once daily medication to prevent the development of HIV cases. It is meant for people who don’t live with HIV but have higher chances of developing the condition.

PrEP helps lower the chances of developing HIV by protecting you and your partners from contracting the virus. It is not for people who already live with HIV.

Today, there are two specific FDA-approved antiviral medications for PrEP. If taken regularly, they are very effective in preventing HIV cases.

Read on to learn more about PrEP medications and how they help lower the chances of contracting HIV.

Drugs used for PrEP belong to a class of antiviral medications called nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs). They work by stopping the virus from multiplying in your body.

Before starting PrEP, and at least every 3 months while you’re taking the medication, you will need to be tested for HIV and have a negative test result.

If you’ve been exposed to HIV or show symptoms of an acute case, you will wait to make sure you test negative before restarting on the PrEP medication.

It’s important to wait for a negative test result because PrEP cannot effectively treat HIV on its own, and drug resistance may develop if PrEP is taken during an HIV case.

Prevention counseling is another important part of PrEP. Before starting PrEP therapy, a healthcare professional can help you:

  • better understand your chances of contracting HIV
  • prevention methods
  • why it might be beneficial to make PrEP part of your daily routine

The length of time you’ll take PrEP will depend on your individual health factors. Talk with a healthcare provider about your health experiences and how long you need to take PrEP.

The two approved PrEP medications are Truvada and Descovy.


Truvada contains the active ingredients emtricitabine and tenofovir disoproxil fumarate. It is available in both brand-name and generic forms.

Truvada comes in multiple strengths, and the dosage is prescribed for HIV treatment or PrEP.

It comes in tablet form and is taken once a day for adults and adolescents who weigh at least 35 kilograms (around 77 pounds). Truvada is approved for both males and females.


Descovy is also a tablet that is taken once daily. It contains the ingredients emtricitabine and tenofovir alafenamide.

Descovy can be used by adults and adolescents who weight at least 35 kilograms (77 pounds). Descovy is not approved for use by females who have greater chances of developing HIV from vaginal sex because effectiveness has not been tested in this group.

According to the Centers for Disease Control and Prevention (CDC), 1.2 million people in the United States contracted HIV in 2018 — and 1 in 7 people didn’t know they contracted the virus.

People who may benefit from PrEP therapy are those who’ve had anal or vaginal sex in the last 6 months and people who:

  • have a sexual partner who has HIV with a detectable viral load or an unknown viral load
  • haven’t used a condom on a consistent basis during sex
  • have contracted a sexually transmitted infection (STI) in the past 6 months

It is also recommended for people who inject drugs and:

  • share needles (syringes)
  • have an injection partner who has tested positive for HIV

If you have been prescribed post-exposure prophylaxis (PEP) multiple times and continue to have higher chances of developing HIV, ask a healthcare professional about starting PrEP.

Pros and cons for HIV PrEP therapy

There can be many factors to consider when starting a new medication. Here are a few things to take into consideration when deciding if PrEP may be right for you:

PrEP is highly effective at preventing HIV when it is taken on a regular schedule as prescribed by a doctor.

According to the CDC, these medications — when taken regularly — lower the chances of contracting HIV from sex by around 99 percent and around 74 percent in people who inject drugs.

However, the medications above are not effective right away. You need to take them daily for at least 7 days for maximum protection from HIV with receptive anal sex.

With injection drug use or receptive vaginal sex, maximum protection occurs after around 21 days with daily use.

Keep in mind that the effectiveness of Descovy among females who have receptive vaginal sex has not been proven.

Truvada and Descovy are generally safe, but some people may experience side effects. Some of these side effects may be serious.

Before starting Descovy or Truvada for PrEP, talk with a healthcare professional about any health conditions you have and the side effects and benefits of PrEP. For example, if you have serious kidney conditions, these medications may not be safe for you to take.

Also, if you’ve contracted hepatitis B in the past, let your doctor know. Stopping Truvada or Descovy may worsen a hepatitis B case.

A healthcare professional will monitor your liver function and can treat the hepatitis B case if it flares up.

It’s important not to take PrEP medications if you live with HIV. This is because the drug may become resistant to the virus if you take it while you live with HIV.

You will have a blood test done before starting the medication and will retest at least every 3 months while you’re taking it.

Possible side effects

Some common side effects of both medications include:

Rare but serious side effects of both include:

These are not all of the possible side effects of Truvada and Descovy. Ask a healthcare professional or pharmacist for more information about these medications, including interactions with other prescribed or over-the-counter medications you take.

If you experience an allergic reaction or other serious side effect to PrEP medications, call 911 or go to an emergency medical center right away.

If you think you may have chances of contracting HIV, it’s important to get regular testing and talk with a counselor or healthcare professional about prevention steps you can take.

Part of your prevention strategy may involve taking PrEP. HIV PrEP is a highly effective medication regimen that can lower your chances of contracting HIV and transmitting the virus to your sexual partners.

Talk with a healthcare professional or make an appointment with a clinic that offers counseling on HIV prevention and your health.