What is PrEP?
PrEP stands for Pre-Exposure Prophylaxis, a type of antiviral medication for HIV prevention. It is specifically designed for individuals who are HIV-negative but have a lifestyle or behaviors that put them at higher risk of contracting HIV. These may include having multiple sexual partners, engaging in unprotected anal sex, or sharing injectable drugs.
Primary purpose of PrEP
The primary goal of PrEP is to reduce the risk of HIV infection before exposure occurs. While PrEP is not a vaccine, it works by inhibiting the virus’s ability to multiply and bind to white blood cells in case it enters the bloodstream.
PrEP must be taken under medical supervision
Although PrEP is highly effective in lowering the risk of HIV infection, it must be taken correctly and consistently under a physician’s guidance to ensure maximum protection and safety.
Do not use PrEP without medical consultation
Since PrEP is an antiviral drug indicated only for HIV-negative individuals, it is essential to undergo health screening and HIV testing before starting the medication. This ensures the individual is not already infected and can safely benefit from PrEP.
How Does PrEP Work in the Body?
Mechanism of action
PrEP works by inhibiting the replication process of HIV within the body. If the virus enters the bloodstream, the medication helps prevent it from binding to and spreading within CD4 cells, which are a key component of the immune system.
Prevents HIV before it spreads
By acting before HIV can infect its target cells, PrEP serves as a proactive line of defense. It is especially effective for individuals at high risk who take the medication consistently as prescribed.
Consistency is key to effectiveness
The effectiveness of PrEP depends largely on regular, consistent use. Skipping doses or stopping the medication can lower the drug levels in the blood, reducing its ability to prevent HIV infection effectively.
Why Take PrEP? Who Should Consider It?
Why is PrEP recommended?
While condom use remains essential, PrEP offers an additional layer of protection for individuals at higher risk of contracting HIV—especially those who may not consistently use condoms. PrEP contributes not only to personal prevention but also plays a broader role in reducing new HIV infections in the community.
According to a 2018 report, Thailand had over 77,000 people living with HIV and continues to see new infections each year. Access to preventive options like PrEP is therefore critical in controlling the spread of HIV.
Who is PrEP recommended for?
PrEP is intended for individuals who are HIV-negative but live a lifestyle that increases their risk of HIV exposure, such as:
- Having multiple sexual partners or frequently changing partners
- Engaging in unprotected anal sex
- Having a known HIV-positive partner
- Injecting drugs and sharing needles
- Participating in high-risk sexual activity or party settings
- Women planning pregnancy while being at high risk of HIV infection
Anyone falling into these categories should consult a healthcare provider to undergo screening and determine if PrEP is suitable for them.
How Effective is PrEP at Preventing HIV?
Clinical studies on PrEP effectiveness
Multiple clinical studies have shown that when taken correctly and consistently, PrEP significantly reduces the risk of HIV infection:
- Over 99% reduction in risk from sexual transmission
- About 70% reduction in risk from injectable drug use
These levels of protection apply particularly when PrEP is taken daily for at least 7 days before potential HIV exposure, allowing sufficient drug concentration in the body.
PrEP is not 100% effective
Although PrEP is highly effective, it does not offer 100% protection against HIV. It also does not prevent other sexually transmitted infections (STIs) such as syphilis, gonorrhea, or herpes. Therefore, the consistent use of condoms is still strongly recommended alongside PrEP.
What’s the Difference Between PrEP and PEP?
Definition of PrEP and PEP
- PrEP (Pre-Exposure Prophylaxis) is an HIV prevention medication taken before potential exposure. It is intended for HIV-negative individuals with ongoing risk behaviors.
- PEP (Post-Exposure Prophylaxis) is an emergency HIV prevention medication taken after potential exposure, such as unprotected sex or a needle injury. It must be started within 72 hours of the incident.
| Criteria |
PrEP |
PEP |
|---|
| Full name |
Pre-Exposure Prophylaxis |
Post-Exposure Prophylaxis |
| When to use |
Before risk occurs |
After risk has occurred |
| Timeframe for initiation |
Must be taken consistently before risk |
Within 72 hours after exposure |
| Duration of use |
Ongoing (daily or during risk periods) |
28 consecutive days |
| Best for |
People with continuous or recurring risk |
People in one-time emergency situations |
| Requires health screening |
Yes |
Yes |
Easy way to remember: PrEP = before, PEP = after
PrEP is a proactive strategy for ongoing risk, while PEP is an emergency response for unexpected exposures, such as sexual assault or accidental unprotected sex.
What Are the Types of PrEP?
Available forms of PrEP
Currently, there are two main types of PrEP designed to suit different lifestyles and risk behaviors: oral tablets and long-acting injections.
1. Oral PrEP
Divided into two dosing strategies:
Daily PrEP (taken every day)
- Take PrEP daily. Start 7 days before sexual activity and continue every day until you stop having sex. You must also continue taking it for 7 days after your last sexual encounter.
- Taken once daily on a consistent schedule
- Maintains steady drug levels in the blood and tissues
- Suitable for individuals with ongoing risk, such as frequent sex or multiple partners
Advantages:
- Provides up to 99% protection when used correctly
Considerations:
- Must be taken at the same time every day for optimal effectiveness
On-Demand PrEP (event-driven dosing)
- Single sexual encounter: Take 2 tablets 2-24 hours before sex. Take the 2nd and 3rd tablets at the same time each day for two more days.
- Continuous sexual activity: Take 2 tablets 2-24 hours before the first sexual encounter. Continue taking 1 tablet every 24 hours until your last sexual encounter, then continue for another 2 days.
- If you take the first 2 tablets but don’t have sex: You can stop taking the medication and don’t need to continue on subsequent days.
- On-Demand PrEP can be confusing: It’s recommended to consult a doctor before starting this regimen for safety.
Advantages:
- Ideal for those with infrequent sexual activity and predictable timing
Contraindications:
- For use by individuals assigned male only.
2. Long-Acting Injectable PrEP
- Involves injections of Cabotegravir every 2 months
- Must be administered by a medical professional
Advantages:
- Eliminates the need to remember daily pills
- Its effectiveness is comparable to or even better than pill PrEP
Considerations:
- May cause redness, swelling, or irritation at the injection site
- Requires adherence to scheduled bi-monthly appointments
How to Use PrEP Effectively and Safely
1. Get a health check-up before starting
Before starting PrEP, individuals must undergo a medical evaluation, which includes:
- HIV testing to confirm negative status
- Screening for other sexually transmitted infections (STIs)
- Liver and kidney function tests
The physician will assess eligibility and recommend the most suitable PrEP regimen based on lifestyle and risk level.
2. Take PrEP consistently
For Daily PrEP users:
- Take the medication daily at about the same time.
- Avoid skipping doses to maintain effective drug levels in the bloodstream
For On-Demand PrEP, follow the 2+1+1 regimen strictly and ensure advance planning before sexual activity.
3. Attend follow-up appointments every 3 months
PrEP users should return for check-ups every 3 months to:
- Repeat HIV testing
- Monitor liver and kidney function
- Evaluate any side effects or medication impact
Regular follow-up ensures continued safety and effectiveness while using PrEP.
What Tests Are Required Before Starting PrEP?
PrEP must be prescribed under medical supervision
PrEP is not available over the counter and must be prescribed by a doctor. It is suitable only for individuals who are HIV-negative, and this must be confirmed before beginning treatment.
Essential tests before starting PrEP
Before a prescription can be given, the following health screenings are required:
1. HIV testing
- To confirm HIV-negative status
- If the result is positive, PrEP is not suitable and a different treatment plan must be initiated
2. Screening for other STIs
- Includes testing for gonorrhea, syphilis, herpes, and hepatitis
- Ensures no existing infections that may interfere with treatment
3. Liver and kidney function tests
- PrEP can affect kidney function in some individuals
- Doctors will assess eGFR (estimated glomerular filtration rate) and liver enzymes before prescribing
Initial prescription and ongoing monitoring
- Doctors will provide PrEP for no more than 3 months at a time
- A follow-up blood test is required before each new prescription to ensure the patient remains HIV-negative and healthy
What Are the Side Effects of PrEP?
PrEP is generally safe under medical supervision
PrEP is considered highly safe when taken under the supervision of a healthcare provider and with regular follow-ups. However, some individuals may experience mild side effects shortly after starting the medication, which typically resolve within a few days.
Common short-term side effects
- Nausea
- Dizziness
- Fatigue
- Mild headaches
- Bloating or stomach discomfort
These symptoms usually appear within the first week and tend to subside as the body adjusts.
When to contact a doctor
Although rare, medical attention should be sought immediately if any of the following occur:
- Unusual urination (e.g., frequent, foamy, or painful)
- Yellowing of the skin or eyes
- Pain in the upper right abdomen
- Unusual fatigue or allergic skin reactions
Monitoring for safety
Doctors will regularly monitor kidney and liver function while patients are on PrEP. If any abnormalities are detected, treatment may be adjusted or discontinued accordingly.
How Long Should You Take PrEP?
Recommended starting period
For those using Daily PrEP, it’s recommended to begin taking the medication at least 7 days before potential HIV exposure. This allows sufficient drug concentration in the bloodstream to offer effective protection.
For On-Demand PrEP, there is no need to build up 7 days in advance—the 2+1+1 schedule can be followed immediately before risk events.
Is PrEP a lifelong commitment?
PrEP is not required for life. It can be discontinued if the individual no longer has significant risk, such as being in a monogamous HIV-negative relationship or having stopped risky behavior.
However, before stopping PrEP:
- Always consult a healthcare provider
- Continue taking PrEP for 28 days after the last potential exposure to ensure full protection
Can you restart PrEP later?
Yes, PrEP can be resumed at any time if risk factors return. Before restarting:
- Undergo appropriate blood tests and health screening
- Follow the same initiation procedures as the first time
What Should You Do If You Forget to Take PrEP?
If you miss a dose of Daily PrEP
- If you remember within 6 hours, take the missed pill as soon as possible
- Do not take two pills at once to make up for the missed one
If you miss a dose in the On-Demand (2+1+1) schedule
- If you forget a post-sex pill (2nd or 3rd dose), take it as soon as you remember
- If more than 12 hours have passed, it’s best to restart the regimen before the next risk exposure
Missed PrEP for more than 7 days?
If you haven’t taken PrEP for over 7 days, it is recommended to:
- Restart the PrEP regimen from the beginning
- Consult a healthcare provider before resuming
- Get tested for HIV and undergo a health check for safety
How Much Does PrEP Cost in 2025?
Price of oral PrEP (30 tablets)
- The cost of PrEP may vary depending on the brand and healthcare provider
- Typical price range:
| Item |
Approximate Cost (THB) |
|---|
| Oral PrEP (30 tablets) |
1,000 – 3,400 THB |
| Pre-PrEP lab test (bloodwork) |
2,000 THB |
Prices do not include doctor consultation fees or additional tests (e.g., liver/kidney function, STI screening)
Factors affecting PrEP pricing
- Brand of medication (Generic vs. Original)
- Type of healthcare provider (private clinic vs. public hospital)
- Eligibility for financial support (e.g., universal coverage, social security)
- Quantity dispensed per visit
Recommendation
Interested individuals are encouraged to check the actual price with their healthcare provider in advance for accurate planning.
Can You Stop Using Condoms If You’re on PrEP?
PrEP protects against HIV—but not everything
While PrEP is highly effective at preventing HIV when used properly, it does not offer 100% protection, and it does not protect against other sexually transmitted infections (STIs), including:
Condoms are still necessary
Condoms remain the first line of defense, providing protection not only against HIV but also against a wide range of other STIs. Combining condom use with PrEP is the safest approach to sexual health.
Recommendation
If you engage in sex with partners whose HIV status is unknown or who are not regular partners, it is strongly advised to:
- Use condoms consistently along with PrEP
- Get tested regularly, ideally every 3 months
Can You Take PrEP During Pregnancy?
PrEP is suitable for women planning pregnancy
Women at risk of HIV who are planning to become pregnant can use PrEP safely, under medical supervision. This is particularly recommended if the partner is HIV-positive or there are ongoing high-risk behaviors.
Safe for the unborn baby
Medical evidence supports that PrEP, particularly with Tenofovir/Emtricitabine, can be safely used during pregnancy without increasing risk to the fetus.
Should be monitored by a healthcare provider
Although generally safe, the following are recommended:
- Inform your doctor if you’re planning to conceive
- Undergo close health monitoring throughout the pregnancy
- Regularly check kidney and liver function, as well as follow-up HIV testing
Is PrEP a Vaccine or a Medication?
PrEP is a medication, not a vaccine
PrEP is an antiviral medication, not a vaccine. Its primary function is to prevent HIV from binding to white blood cells if the virus enters the body. Unlike vaccines, it does not stimulate the immune system to produce antibodies.
Key differences between PrEP and vaccines
| Aspect |
PrEP |
Vaccine |
|---|
| Type |
Antiviral drug |
Immune-stimulating agent |
| Mechanism |
Prevents viral replication |
Trains the immune system to resist infection |
| Frequency |
Taken regularly |
Usually administered once or annually |
PrEP must be taken consistently
To be effective, PrEP needs to be used consistently, especially before high-risk periods. If planning to discontinue, always consult a healthcare provider first.
Frequently Asked Questions About PrEP
Q: How soon does PrEP start working?
A: For Daily PrEP, it takes at least 7 days of consistent use before HIV protection becomes effective.
Q: How often do I need HIV testing while on PrEP?
A: You should get tested every 3 months to ensure continued effectiveness and confirm HIV-negative status.
Q: Can I stop PrEP and restart later?
A: Yes, but you should consult a healthcare provider and get re-tested for HIV before restarting.
Q: Can I drink alcohol while taking PrEP?
A: Yes, moderate alcohol consumption is safe. PrEP does not interact directly with alcohol, but always remember to take your pill—even on drinking days.
Q: Can women use PrEP?
A: Yes, PrEP is safe for both men and women, including those planning pregnancy, as long as it’s used under medical supervision.
Real User Reviews: Experiences with PrEP
“Started PrEP on a friend’s advice and feel so much more at ease now”
“I was worried about side effects at first, but the doctor explained that I might feel a little nauseous at the beginning. After the first week, I felt totally fine. Now I take PrEP daily with my vitamins, and I feel more confident when meeting new partners—still always using condoms.”
“Used to forget doses, but setting reminders helped a lot”
“I’m on Daily PrEP. In the beginning, I forgot doses often. Then I started using a nightly phone alarm—problem solved. If you tend to forget, find a reliable reminder system.”
“Using On-Demand PrEP because I don’t have frequent sex”
“I don’t have sex regularly, so I use the 2+1+1 schedule. It’s easier to manage, but you do need to plan ahead.”
Can You Buy PrEP Online? Is It Safe?
PrEP should not be purchased without a prescription
Although PrEP is sold on some websites, it should only be used under medical supervision, because:
- An HIV test is required to confirm negative status
- Overall health must be evaluated, especially kidney and liver function
- Ongoing follow-up is necessary to ensure safety
Taking PrEP without medical assessment may lead to undiagnosed HIV infection or ineffective drug use
Risks of buying PrEP online
- Possible risk of receiving counterfeit or expired medication
- Source and quality of the product cannot be verified
- No professional guidance on usage or monitoring
Recommendation
To use PrEP safely:
- Visit a certified clinic or hospital for proper evaluation
- Never start PrEP without HIV testing
- Avoid ordering from unverified or informal sources
Is Free PrEP Available? What Coverage Options Exist?
Free PrEP is available in specific cases
In Thailand, both government and NGO programs offer free or subsidized PrEP for high-risk populations such as:
- Men who have sex with men (MSM)
- People who inject drugs
- Individuals with HIV-positive partners
- Vulnerable youth groups
Coverage and eligibility options
| Coverage Type |
Eligibility or Conditions |
|---|
| Universal Health Coverage (UHC) |
Available at selected government hospitals/clinics |
| Social Security Scheme |
Depends on the individual’s healthcare network |
| NGOs and specialized community clinics |
Free or co-pay programs for specific groups |
Recommendation
- Inquire at local health facilities or clinics offering PrEP
- Prepare necessary documents such as a national ID or insurance card
- Confirm whether you fall within a program’s target eligibility group
Comparing PrEP Brands in Thailand (2025)
Available brands in Thailand
In Thailand, PrEP is available in both original brands and generic formulations, all approved by the Thai Food and Drug Administration (FDA).
Commonly used brands:
| Brand Name |
Type |
Active Ingredients |
Notes |
|---|
| Truvada |
Original brand |
Tenofovir + Emtricitabine |
Higher cost; long-term research data |
| Ricovir-EM |
Generic |
Tenofovir + Emtricitabine |
Widely used across Asia; affordable |
| Tenof-EM |
Generic |
Tenofovir + Emtricitabine |
Similar price to Ricovir-EM |
| Teno-EM |
Generic |
Tenofovir + Emtricitabine |
Another common generic alternative |
How to choose the right brand
- Source reliability: Always obtain PrEP from licensed clinics or hospitals
- FDA approval: Ensure the brand is registered and approved for use in Thailand
- Doctor’s advice: The best choice may vary depending on individual health conditions
Conclusion
PrEP is a medically proven, highly effective tool for significantly reducing the risk of HIV infection—especially when combined with regular health check-ups and responsible sexual behavior.
Although PrEP does not protect against all sexually transmitted infections, it provides an added layer of security for at-risk individuals and reflects a proactive approach to personal and public health responsibility.
Reference:
