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How Does PrEP Work in Preventing HIV?

What is PrEP?

PrEP or Pre-exposure prophylaxis is a medication taken daily to prevent the development of HIV cases. It is recommended for people who do not have HIV but are at risk of developing it.

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 did not even know they have contracted the virus.(1)

PrEP or Pre-exposure prophylaxis helps by lowering the chances of developing HIV and protecting both partners from getting the virus. It cannot be used for those who are already living with the virus.

There are two antiviral medications for HIV, which if taken regularly are effective in preventing HIV cases.

How Does PrEP Work in Preventing HIV?

How Does PrEP Work in Preventing HIV?

Drugs used in PrEP are the class of antiviral medications that are called nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs). They work by stopping the virus multiplication in the body.

Before taking the medication you need to be tested for HIV and should have a negative test. Also, while taking the medications you need to get tested every 3 months.

It is important to be tested negative before taking PrEP as these drugs do not treat HIV on their own and increases the chances of developing drug resistance if HIV case takes PrEP.

For people who do not have HIV taking antiretrovirals (ARV) increase the level of the drug in their bloodstream, genital tract, and rectum. If the exposure of HIV occurs the ARVs stop the virus from entering and replicating. This prevents HIV from establishing in a person.

Before starting a PrEP therapy, it is important to consult a healthcare professional as he can help you understand:

  • Chances of contracting the virus
  • Prevention method
  • Importance of PrEP as a daily routine

How long a person can take PrEP depends on a person’s health.

These medicines are not effective right away. They need to be taken for at least 7 days for maximum protection from HIV.(2) For receptive vaginal sex, maximum protection occurs after 21 days of regular use.

Different Types of PrEP

There are two medicines that are approved as PrEP medications, which are:


Truvada has emtricitabine and tenofovir disoproxil fumarate as active ingredients. It comes in multiple strengths. Its dosage depends on the HIV treatment or PrEP.


Active ingredients in descovy are emtricitabine and tenofovir alafenamide.

It can be used by adults and adolescents with at least 35kg of weight. It is not approved to be used by females.

Who is a Good Candidate for PrEP?

People who have had anal or vaginal sex in the last 6 months are good candidates to benefit from PrEP therapy. It can also be beneficial for:

  • Those who have a sexual partner who has HIV with detectable viral load
  • Those who haven’t used a condom during sex
  • Those who have contracted sexually transmitted infection in the past 6 months

It can also be recommended for those people who inject drugs and share needles or for those who have an injection partner who has tested positive for HIV.

Those who have been prescribed PrEP multiple times and continue to have higher chances of developing HIV should consult a healthcare provider about starting it again.

Pros and Cons of PrEP Therapy

There are many factors that should be considered when starting any new medications. All its pros and cons should be taken into consideration.

Pros of PrEP Therapy

  • These medicines are very effective in preventing HIV cases
  • It can protect both the partners from HIV transmission
  • It is convenient to take
  • It can be an option for serodiscordant people (those having mixed HIV status), who want to have a baby

Cons of PrEP Therapy

  • The brand-name Truvada and Descovy can be expensive and also are not covered by insurance
  • One has to remember to take it every day
  • A person has to undergo regular HIV testing
  • These medications have side effects
  • They may not be good for those with serious kidney disease and hepatitis B

Side effects of PrEP

Medicines used in PrEP are mostly safe but can lead to side effects in some people. In some, the side effects can be serious too.

Some common side effects of both medicines used in PrEP are:

Rare but serious side effects include:

  • Allergic reaction
  • Liver and kidney problem
  • Lactic acidosis
  • Worsening of Hepatitis B

If someone notices any allergic reaction, emergency medical center should be reached immediately.

PrEP is a highly effective medication regimen that can lower the chances of contracting HIV and transmitting it to a sexual partner.

Team PainAssist
Team PainAssist
Written, Edited or Reviewed By: Team PainAssist, Pain Assist Inc. This article does not provide medical advice. See disclaimer
Last Modified On:October 1, 2021

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