PrEP (Pre-Exposure Prophylaxis)
PrEP is a highly effective medicine (>99%) that reduces the risk of acquiring HIV in HIV-negative people; daily, 2-1-1, and injectable regimens are available.
What is PrEP?
PrEP is a medicine that reduces the risk of acquiring HIV very effectively when used correctly.
It is intended for HIV-negative people who have a higher risk of exposure to the virus.
How does it work?
- HIV enters the body.
- PrEP keeps medicine in the body.
- It prevents HIV from becoming established and replicating.
- Infection does not occur.
Which medicines are available?
| Medicine | Presentation | Use | Duration |
|---|---|---|---|
| TDF/FTC (Tenofovir disoproxil fumarate 300 mg / Emtricitabine 200 mg) | Daily oral tablet | Daily PrEP (continuous use) | Ongoing protection while taken every day |
| TAF/FTC* (Tenofovir alafenamide 25 mg / Emtricitabine 200 mg) | Daily oral tablet | Daily PrEP (for some people) | Ongoing protection while taken every day |
| CABOTEGRAVIR LA (Cabotegravir 600 mg, long-acting injection) | Intramuscular injection | Injectable PrEP every 2 months | Ongoing protection with doses every 2 months |
*TAF/FTC has specific indications and does not replace TDF/FTC for every population.
How is it used?
Daily PrEP
Take 1 tablet every day, ideally at the same time.
Protection is reached after:
- 7 days of daily use for anal sex.
- 20 days for vaginal sex.
2-1-1 PrEP
Only for cisgender gay and bisexual men and other men who have sex with men.
Schedule:
- 2 tablets between 2 and 24 hours before sex.
- 1 tablet 24 hours later.
- 1 tablet 24 hours after the second dose.
It is not for everyday use. Always consult a healthcare professional.
Cabotegravir LA (Injectable PrEP)
Injection in the buttock every 2 months.
Protection starts after the first injection and the second injection (4 weeks later).
It requires follow-up in healthcare services.
Common side effects (usually mild and temporary)
- Nausea
- Headache
- Gastrointestinal discomfort
- Fatigue
If side effects worry you or do not improve, talk with your healthcare professional.
What follow-up is recommended?
| Check | Frequency |
|---|---|
| HIV | Every 3 months (minimum) |
| Kidney function | Every 6 months (or as indicated) |
| STIs | Every 3-6 months or according to your risk |
| Hepatitis B and C | According to your situation |
| Pregnancy | When relevant |
The frequency of follow-up may vary depending on the person, the medicine used, and the healthcare team’s criteria.
Key self-care messages
- Do not stop PrEP because you use substances. Keep taking it as indicated.
- Set reminders for your doses. Adherence is key for it to work.
- Carry a dose with you if you know you will be away from home or travelling.
- If you vomit within 1-2 hours after taking the tablet, ask what to do based on the time that passed.
- PrEP protects against HIV, but not other STIs. Use condoms and get regular check-ups.
- If you have questions, side effects, or a special situation, talk with your healthcare team.
Did you know? PrEP effectiveness is higher than 99% for sexual transmission of HIV when used correctly and with good adherence.
Biomedical HIV prevention: general context
These are medicine-based strategies that reduce the risk of acquiring or transmitting HIV when used correctly and consistently.
Available strategies
| Strategy | Description |
|---|---|
| PrEP | Pre-Exposure Prophylaxis. Medicines for HIV-negative people that prevent infection. |
| PEP | Post-Exposure Prophylaxis. Emergency medicines after a possible HIV exposure (ideally within 72 hours). |
| ART (TasP) | Treatment as Prevention. People living with HIV who are on treatment and have an undetectable viral load do not transmit the virus. |
| CAB-LA | Long-acting cabotegravir. Injectable PrEP every 2 months to prevent HIV. |
| DOXY-PEP* | Post-exposure doxycycline. An antibiotic used after some practices to reduce the risk of bacterial STIs. It does not prevent HIV. |
*Doxy-PEP does not prevent HIV, but it may complement other sexual health strategies.
PrEP: what you should know
- For HIV-negative people with a risk of exposure.
- Highly effective (>99%) when used correctly.
- Requires regular HIV tests and health follow-up.
- It does not protect against other STIs.
- Different forms and schedules exist (daily, 2-1-1, and injectable).
Cabotegravir (injectable PrEP)
Cabotegravir is a long-acting medicine given by injection every 2 months. It offers very high protection and is an option for people who prefer not to take daily pills.
Interactions between psychoactive substances and HIV prevention medicines
| Substance | Daily oral PrEP TDF/FTC | Daily oral PrEP TAF/FTC | Injectable PrEP CABOTEGRAVIR | PEP TDF/FTC + DOLUTEGRAVIR | PEP TDF/FTC + RALTEGRAVIR | Does it affect adherence? | What to do? |
|---|---|---|---|---|---|---|---|
| Alcohol | Caution | Caution | Caution | Caution | Caution | May lead to forgotten or delayed doses. | Drink in moderation. Use reminders. Do not skip doses. |
| Cannabis | Low | Low | Low | Low | Low | Low impact on adherence. | No changes needed. Keep your routine. |
| Cocaine | Caution | Caution | Caution | Caution | Caution | May increase disinhibition and lead to missed doses. | Set reminders. Keep your medicine with you. |
| MDMA / Ecstasy | Caution | Caution | Caution | Caution | Caution | Risk of dehydration and missed doses. | Stay hydrated, rest, and keep your regimen. Do not stop it. |
| Methamphetamine | Moderate | Moderate | Moderate | Moderate | Moderate | High risk of missed doses and interruptions. | Use alarms and support from trusted people. |
| Ketamine | Low | Low | Low | Low | Low | May affect memory at high doses. | Plan your dose. Do not make decisions while under the effects. |
| GHB / GBL | Caution | Caution | Caution | Caution | Caution | Loss of consciousness may lead to missed doses. | If there is risk, make sure someone knows about your treatment. |
| Poppers (nitrites) | Low | Low | Low | Low | Low | Low impact on adherence. | Do not combine poppers with PDE5 inhibitors. |
| Opioids | Caution | Caution | Caution | Caution | Caution | Sedation may lead to missed doses. | Use reminders. Do not interrupt treatment. |
| LSD | Low | Low | Low | Low | Low | Low impact on adherence. | No changes needed. |
| Inhalants | Moderate | Moderate | Moderate | Moderate | Moderate | Cognitive impairment may lead to missed doses. | Plan ahead and keep support available. Do not interrupt treatment. |
This table does not include every possible substance. Evidence may change. Always consult healthcare professionals.
Recommended follow-up
- HIV test every 3 months and hepatitis B testing at minimum.
- Kidney function every 6 months as indicated.
- STIs: regular screening.
- Adherence and mental health review.
- Hepatitis A and B vaccination.
Common side effects
These may include nausea, headache, tiredness, and gastrointestinal discomfort. They are usually mild and temporary. If they are severe or persistent, talk with your healthcare professional. Do not stop without guidance.
Support resources
- LGBTIQ+ helplines and support
- Inclusive sexual health services
- Community harm reduction organisations
- Check our allies network
This information is educational and does not replace medical advice. Every body is different and recommendations may vary. Always consult a healthcare professional for personalised guidance.