How HIV PrEP Works

The HIV medication Truvada was first approved for use by the Federal Drug Administration in August 2004. Made by California-based pharmaceutical giant Gilead Sciences, Inc., Truvada contains two active drugs, emtricitabine and tenofovir disproxil fumarate and was originally approved for use as an antiretroviral agent. Antiretrovirals are in a drug classification of medications used to treat HIV and AIDS.

All HIV medications work by disabling the steps the virus takes when hijacking uninfected cells. The goal of antiretroviral treatment is to keep the amount of HIV in the body at a low level to help stop the weakening of the immune system, which can lead to the development of AIDS, and to allow the immune system to recover from any damage that HIV might have already caused.

There are more than 20 FDA-approved antiretroviral medications in use today. When only one antiretroviral medication is used to treat HIV, the virus can become resistant to that medication, making it ineffective over time. Taking two or more antiretroviral medications at one time is called combination therapy. The goal of combination therapy is to limit the rate at which HIV becomes resistant to the medications and, therefore, making treatment more effective over a longer period of time.

Since its approval in 2004, Truvada has shown great promise in reducing the risk of acquiring an HIV infection. The medication works so well in suppressing HIV infections in the blood that HIV-positive people who regularly take Truvada can show negative results on HIV blood tests, which renders them nearly noninfectious despite their being HIV-positive in status.

In July 2012, Truvada became the first FDA-approved drug used daily for pre-exposure prophylaxis (PrEP) to reduce the risk of sexually-acquired HIV infection in adults at high risk of developing HIV, especially though engaging in sexual encounters with HIV-infected individuals. PrEP works best when used in combination with safer sex practices.

PrEP studies have been and are still being conducted in Africa, Asia, South America and North America to illustrate how Truvada works as a preventative medication in the battle against the spread of HIV. These studies included people who may have been exposed to HIV through unprotected anal and/or vaginal sex and through sharing used needles for the injection of drugs. Some participants in these studies are heterosexual serodiscordant couples, in which one person is HIV positive and the other is HIV negative.

The iPrEX study compared Truvada with a placebo, or sugar pill with no medical benefits, in nearly 2,500 gay and bisexual men and transwomen in six countries. The participants all received safer sex education as part of this study. Among the participants in the study with detectable levels of Truvada in their blood, which means they regularly took the medication, HIV transmissions dropped by as much as 92 percent.

One study, Partners PrEP, focused on more than 4,500 heterosexual men and women from Uganda and Kenya who were involved in serodiscordant relationships. Looking at the results from just the men and women who took Truvada, the researchers in this study found a reduction in new HIV infections by 75 percent. This study found that good medication adherence, for example taking medication at the same time every day, really made a difference in the ability of Truvada to prevent HIV infection. The better the adherence, the higher the rate in reduction in new HIV infections.

A similar study conducted in Botswana, called TDF2, found similar efficacy rates for Truvada among heterosexual men and women as the Partners PrEP study found. In the TDF2 study, the risk of HIV infection dropped by around 62 percent among Truvada users.

Successful studies as well as the three studies that failed due to low adherence in medication use illustrate that Truvada only works as PrEP therapy when taken consistently. Irregular use of PrEP offers no real value of protection to users. When combined with safer sex practices, PrEP is most effective in limiting HIV infection in those who are uninfected and at the highest risk of contracting the virus.

As the use of PrEP becomes more widely accepted, the pros and cons of its use are increasingly being discussed in gay and bisexual communities across the nation.

The obvious pro for the use of PrEP is the reduction of new HIV cases among PrEP users who are HIV-negative. Earlier this month, Kaiser Permanente’s San Francisco Medical Center reported “no new HIV diagnoses among PrEP users” among the 657 gay and bisexual men who participated in the Kaiser PrEP Study, which began in 2012.

The study illustrates how PrEP works in a “real-world” setting and shows the promise of the drug in giving sexual freedom to an entire generation of gay and bisexual men who came of age during the AIDS epidemic. Some of those men have shared in recent news articles that they think of HIV during every sexual encounter and how that fear invades their sexuality.

Some researchers believe continued studies of PrEP and how it works within the body can help scientists develop a vaccine to prevent HIV altogether.

One of the cons of the use of PrEP is the cost of Truvada, which has an average list price at of $1,454 for a month’s supply. Most private insurance companies and all state Medicaid programs will cover PrEP, although some insurance companies require prior authorization before the medication can be dispensed by pharmacies.

There is a co-pay assistance program sponsored by Gilead, the maker of Truvada, for patients with commercial insurance who wish to receive PrEP but who may not be able to afford the co-pays. Patients with state and federal prescription benefits, such as Medicaid and Medicare, are not eligible for co-pay assistance programs of any kind.

In addition to its co-pay assistance program, Gilead offers a Truvada for PrEP Medication Assistance Program for eligible HIV-negative uninsured adults in the United States who wish to obtain Truvada for use as PrEP.

The use of Truvada has been linked to mild kidney damage in a small percentage of people who take the drug as part of their HIV-treatment regime. Some patients will require regular testing to monitor their kidney function.

Another con to the use of PrEP has been suggested by Pittsburgh-area reader Brian and is based upon his personal experiences with other men who are taking PrEP.

“Young men ages 18 to 23 seem to think of PrEP as the male pill,” said Brian, citing the correlation between the birth control pill only preventing pregnancy and doing nothing for women in the battle against sexually transmitted infections (STIs) as being similar to how PrEP can only prevent an HIV-infection and doing nothing to prevent contracting other STIs in gay and bisexual men.

Brian believes these young men see Truvada as a salvation that will protect them from disease even if they are unsafe in their sexual encounters, such as not using condoms during anal sex. This lack of sexual education as well as an increase in uninhibited sexual behavior has been cited for an increase in other sexually transmitted diseases, such as syphilis, among young gay and bisexual men who are taking PrEP.

For example, some men participating in the Kaiser PrEP Study reported a drop in condom use and rates of STIs were high among study participants. A total of 344 STI diagnoses were made during the study, which required participants to obtain frequent STI testing and to receive prompt treatment in cases of infection.

PrEP, when taken consistently, has been shown in multiple studies to protect HIV-negative men and women against infection from the virus. Although this protection can lure some PrEP users into the illusion of complete sexual freedom, it is still very important for PrEP users to continue to stay safe during their sexual encounters by using condoms with partners who are HIV-positive, even if the virus is suppressed, or when sex is happening outside of monogamy in order to reduce the risk of contracting other STIs.

It’s ok to explore one’s sexuality, as long the exploration itself is handled responsibly and safely.



  1. The Truth About HIV Transmission | Your Sexy Librarian - […] people who are regularly taking antiretroviral medications, such as Truvada used as PrEP, can have very low viral loads,…
  2. The Legalities of HIV Infection | Your Sexy Librarian - […] of HIV, such as daily antiretroviral use that can result in a low viral load and the use of…

Submit a Comment