PEP: Emergency HIV Medicine After Exposure, Start Within 72 Hours

The message I receive most often late at night is "The condom broke. What do I do?" I understand that panic well. The first thing I want to tell you is: stay calm, and do not wait. You still have a way to prevent HIV with PEP, which works very well if you start early. This article explains everything you need to know, from who should use it to the tests after you finish the course.

What is PEP?

PEP stands for post-exposure prophylaxis: taking HIV antiretroviral medicine after an exposure to stop the virus before it can establish itself permanently in the body. The window in which the medicine can work is limited, so you need to start as soon as possible, ideally within 24 hours, and no later than 72 hours. After that, the benefit drops so much that most guidelines do not recommend starting.

Who should receive PEP?

PEP is for a risk with a partner who has HIV and is not virally suppressed, or whose status is unknown, for example:

• Anal or vaginal sex without a condom, or a condom that broke, leaked or slipped off
• Sexual assault
• Sharing needles or injecting equipment with others
• A large amount of blood or body fluid getting into a mucous membrane or an open wound

Very low-risk situations, such as kissing, normal skin contact or oral sex without sores, usually do not need PEP. A doctor will assess each case. If your partner has HIV and has had an undetectable viral load on treatment continuously, there is no risk of sexual transmission, according to U=U. People already using PrEP correctly usually do not need PEP.

Steps to get PEP

1. Check the time. How many hours ago did it happen? If it is less than 72 hours, contact a doctor straight away.
2. Risk history. The type of exposure, your partner's status if known, health conditions, current medicines and pregnancy.
3. HIV test before starting, with a blood test or fingerstick kit, to check you did not already have HIV (this result does not tell you whether you were infected this time). But you do not need to wait for other lab results before starting. Read about test kits in HIV self-test.
4. Start the medicine immediately and take it once a day for the full 28 days.
5. Additional tests: kidney and liver function, hepatitis B and C, syphilis and other STIs as appropriate.
6. Follow-up after finishing: repeat HIV tests as scheduled.

Which medicines are used?

Current guidelines from the US CDC (2025), the WHO and Thailand recommend three drugs. The most commonly used regimen is:

• Tenofovir (TDF or TAF) + lamivudine or emtricitabine + dolutegravir, once a day
• Other options as appropriate, such as bictegravir/emtricitabine/TAF

Dolutegravir-based regimens have few side effects, and several brands combine everything in a single tablet. Older regimens containing efavirenz are no longer recommended for PEP, because they cause dizziness and strange dreams and are less well tolerated. Read how brands differ in Do PrEP/PEP brands differ?

Side effects and precautions

• At first you may have nausea, diarrhoea, headache, tiredness or trouble sleeping. These usually improve within a few days.
• Dolutegravir binds to minerals such as antacids, calcium, iron, magnesium, zinc and multivitamins. Take them apart as your doctor or pharmacist advises (generally dolutegravir 2 hours before, or 6 hours after). See more about supplements in Calcium, zinc and vitamin D.
• Tell your doctor if you take other regular medicines, are pregnant or are breastfeeding.
• If you get a severe rash, yellow eyes or skin, severe abdominal pain, or vomiting so much you cannot keep the medicine down, contact your doctor immediately.

What if I forget a dose?

Take it as soon as you remember, unless it is nearly time for the next dose, then carry on at your usual time. Do not take two tablets at once. If you miss several days in a row, talk to your doctor. Do not stop before 28 days, even if your partner has tested negative, unless a doctor has assessed that you can stop.

Follow-up tests

The CDC 2025 guideline recommends watching for symptoms early on and repeating the HIV test at about 4–6 weeks and 12 weeks after the exposure. Thai practice commonly tests at about 1 and 3 months. If you get a fever, sore throat, rash or swollen lymph nodes during or after the course, test sooner. Read about test timing in HIV window period and when to test.

While you wait for results, use condoms every time, and get tested for syphilis, gonorrhea and chlamydia at the right times. For some groups, Doxy-PEP can be considered within the same 72 hours.

If you were sexually assaulted

Please go to a hospital as soon as possible. As well as PEP, you should receive care for any injuries, emergency contraception, hepatitis B vaccination, medicine to prevent STIs, and evidence collection if you want to take legal action. Thai government hospitals have One Stop Crisis Centres (OSCC). You can call 1300, Thailand's 24-hour social assistance hotline. In an emergency call 1669 (medical) or 191 (police); the Tourist Police can also be reached on 1155 for help in English. It is not your fault, and you do not have to go through this alone.

After 28 days

If the risk could happen again, I recommend switching to PrEP the very next day, with no gap, once your HIV test is negative. Read the differences and how to choose in PrEP vs PEP.

How the clinic can help

At Dr. Kris Clinic, I assess your risk, test for HIV before starting medicine, prescribe PEP according to guidelines and arrange follow-up tests, both at the clinic in Surat Thani and through telemedicine with discreet, unlabelled delivery of medicine. English-speaking consultations are available. Because time matters so much, contact us as soon as possible after the event. See all the steps again in Just had an HIV exposure? What to do now.