Everything you need to know about preventing HIV with PrEP

PrEP is effective

It has been proven that for people at high risk of acquiring HIV through sex, PrEP is 99% effective at preventing HIV if the medication is taken every day (seven doses per week). It is 74% effective (if taken daily) for HIV prevention after injecting drugs. Its effectiveness is lower if it is taken not regularly.¹

• Daily use of PrEP (seven days per week) is 99% effective.
• If the medication is taken four times a week, it is 96% effective at preventing contraction of HIV through anal sex.
• If taken only two times a week, its effectiveness drops to 75% for men and even lower for women.^{2, 3}

HPrEP medication should be taken regularly

Four doses of PrEP per week are sufficient for reliable prevention of HIV in people who are having anal sex. Put another way, PrEP is highly effective if you are having anal sex and you miss fewer than 3 doses per week (not more than 12 doses per month).⁴ For women having vaginal sex, PrEP is 85% effective when 6 of 7 doses a week are taken, suggesting that daily usage (7 doses a week) is a must for reliable prevention. Try not to miss more than one dose per week (three to four doses per month) if you are having vaginal sex.^{3, 5}

PrEP is not immediately effective

For people who have anal sex, PrEP becomes highly effective after seven days if it is taken every day. It takes longer to become effective—21 days of daily use—to be effective at preventing HIV after injection of drugs or in people having vaginal sex. And you should be aware that this data applies only to the partner having receptive sex (i.e., receiving the penis) because there is no accurate data for the partner having insertive sex (i.e., inserting the penis).

Advantages and disadvantages of Truvada and Descovy

Truvada and Descovy are the primary medications used for PrEP and, in combination with other agents, HIV treatment. Descovy is a modified version of Truvada and has several advantages:

• Descovy is less toxic to kidneys and bone tissue than Truvada
• Descovy is slightly more effective (99.7% compared to 99.4%)
• A lower dosage of Descovy is necessary to achieve the same effect, which explains why it is less toxic
• The Descovy pill is smaller and therefore easier to swallow

Descovy’s disadvantage is that it cannot be used as PrEP for the prevention of HIV acquisition through vaginal intercourse (it is not approved for that use).⁶ Truvada can be used for that purpose.

Who should take PrEP

Consider taking PrEP if you are homosexual or bisexual and:

• Your partner is diagnosed with HIV
• You are having sexual intercourse with several partners
• Your partner is having sexual intercourse with several partners
• You had unprotected anal sex with several partners whose HIV status is unknown
• You acquired an STD during the last six months
• You inject drugs and share needles for injecting them

Consider taking PrEP if you are heterosexual and:

• Your partner is diagnosed with HIV
• You are having sexual intercourse with several partners
• Your partner is having sexual intercourse with several partners
• You had unprotected sex with a bisexual male partner
• You had unprotected sex with a person who injects drugs
• You inject drugs and share needles for injecting them¹⁰

Using PrEP when you are planning one-time sex that might expose you to HIV

Based on recent clinical trials, if you are a man who has sex with men and you are planning a one-time sexual encounter that might expose you to HIV, you can take Truvada (not Descovy) on a 2-1-1 schedule.

Two Truvada pills should be taken 2–24 hours before you have sex, followed by one pill each day for the next two days.¹¹

If you are planning to have sex on several days, take two pills 2–24 hours before having sex, take one pill on each additional day that you have sex, and then continue taking one pill daily for two more days after the last time you have sex.⁹

How you can get PrEP medication

PrEP must be prescribed by a physician. Our healthcare providers will be happy to answer all your questions and perform all the tests you should have before beginning PrEP medication.

The cost of PrEP

Health insurance covers all the costs related to PrEP medication. Gilead’s Advancing Access program makes medicine even more affordable, regardless of insurance. If you meet the eligibility criteria, your co-pay (lab tests, doctor visits, and medication) may be $0.

Necessary tests

PrEP can be prescribed only to people who are HIV-negative. Therefore, you should get tested for HIV before the initiation of PrEP. Fourth-generation combined antigen/antibody tests or viral load tests are commonly used for this purpose. Rapid tests are not suggested.9 For accurate results, stop having sex for at least two to three weeks and then get tested with fourth-generation combined tests; if you are HIV-negative, you can start PrEP. Note that PrEP doesn’t protect you from other STDs or pregnancy. Therefore, you are encouraged to use condoms while taking PrEP.

You should retake the HIV detection test three months after receiving PrEP.

As mentioned above, PrEP medications can be toxic to kidneys. Therefore, your creatinine level should also assessed to evaluate how well your kidneys are functioning.

References

1. Pre-Exposure Prophylaxis (PrEP) | HIV Risk and Prevention | HIV/AIDS | CDC.

2. PrEP: Answers About Pre-Exposure Prophylaxis for HIV. WebMD

3. A Translational Pharmacology Approach to Predicting Outcomes of Preexposure Prophylaxis Against HIV in Men and Women Using Tenofovir Disoproxil Fumarate With or Without Emtricitabine - PubMed.

4. Grant RM, Anderson PL, McMahan V, et al. Uptake of pre-exposure prophylaxis, sexual practices, and HIV incidence in men and transgender women who have sex with men: A cohort study. Lancet Infect Dis.

5. Administration of pre-exposure prophylaxis against HIV infection - UpToDate.

6. PrEP | HIV Basics | HIV/AIDS | CDC.

7. TRUVADA for PrEP® Side Effects.

8. Learn About Different Uses for DESCOVY®.

9. Patient evaluation and selection for HIV pre-exposure prophylaxis - UpToDate.

10. Pre-Exposure Prophylaxis | HIV.gov.

11. “On-Demand” Dosing for PrEP: Guidance for Medical Providers.