Infections · Medication Guide
Metronidazole in Thailand
What metronidazole is, the infections it treats, why alcohol is off-limits while you take it, and how men in Bangkok get it legally. Reviewed by a licensed physician at a MOPH-registered men's health clinic.
- Symptoms often ease within days
- Thai FDA registered · prescription only
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Medically reviewed by Dr. Noppon Arunkajohnsak (Win)
Menscape Clinic
Last reviewed
11 July 2026
1960s
In clinical use since
one of the oldest anti-anaerobic drugs
~8 h
Elimination half-life
cleared steadily over about a day
90–95%
Trichomoniasis cure rate
when both partners are treated
48 h
Alcohol-free window after
to avoid a disulfiram-like reaction
Key takeaways
Metronidazole is a prescription nitroimidazole antibiotic for anaerobic bacterial and protozoal infections, not colds, flu, or ordinary bacterial infections.
Do not drink alcohol while taking it or for 48 hours after: the mix can cause a disulfiram-like reaction with flushing, nausea, vomiting, and a racing heart.
In Thailand it is a dangerous drug (ยาอันตราย). It must come from a pharmacist or a doctor, and unlicensed online sellers are illegal and a counterfeit risk.
A doctor must confirm which infection you have. Many infections feel similar but need a different antibiotic, so self-treating often wastes time and drives resistance.
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What metronidazole is & how it works
Metronidazole is a prescription antibiotic and antiprotozoal from the nitroimidazole family. It treats infections caused by anaerobic bacteria (organisms that thrive without oxygen) and by protozoa, the single-celled parasites behind trichomoniasis, amoebic dysentery, and giardiasis.
It is a targeted drug, not a catch-all. Metronidazole is inactive against the ordinary aerobic bacteria behind most sore throats, chest infections, and simple urinary infections. That is why a doctor first identifies the organism: used for the wrong infection, it simply will not work.
In men, it comes up most often for the protozoal sexually transmitted infection trichomoniasis (where both partners must be treated), for gut infections picked up from food or water, as part of combination therapy for H. pylori, and for anaerobic infections such as dental or abdominal abscesses.
In practice it is usually a short oral course of tablets taken with food, most often over about 5–10 days depending on the infection. It has been in clinical use since the 1960s and stays a first-line choice for the organisms it targets, which is why a doctor still reaches for it once the infection is confirmed by testing.
Enters the microbe
The small molecule is absorbed from the gut and diffuses into anaerobic bacteria and protozoa.
Activated inside
Low-oxygen organisms chemically reduce metronidazole into a reactive form. Human cells and aerobic bacteria mostly do not.¹
Damages the DNA
The reactive form breaks the microbe's DNA strands, halting its ability to survive and reproduce.
Microbe dies
Anaerobes and protozoa are killed selectively, largely sparing the normal oxygen-using flora.
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Getting metronidazole in Thailand
Thai FDA status
Registered with the Thai FDA and classified as a dangerous drug (ยาอันตราย). Oral tablets, including a 400 mg strength, are available through licensed channels, and it is sold in Thailand under brands such as Flagyl.²
Where it's legal to get
From a licensed pharmacy (first-class pharmacist) or prescribed by a doctor at a licensed clinic. Teleconsultation with licensed telepharmacy delivery is also legal.³
For expats & visitors
No Thai residency is required. It is commonly used for traveller's gut infections such as amoebiasis and giardiasis, and for STI partner treatment. Bring any test results or diagnosis you already have.
Thai FDA warning. The regulator has repeatedly warned against buying prescription antibiotics from unlicensed online sellers. Counterfeit and sub-standard products are common, and nobody is accountable for what you receive.⁴
03
Does it work? The evidence
Metronidazole is a long-established treatment on the WHO Model List of Essential Medicines. For trichomoniasis, treatment guidelines report cure rates of roughly 90–95% when both sexual partners are treated at the same time, which stops the infection bouncing back and forth.⁵
It is similarly effective against the protozoa behind amoebic dysentery and giardiasis, with clearance around 90% once a full course is completed. Two things matter for the result: finish the entire course even after symptoms settle, and for a sexually transmitted infection treat the partner and avoid sex until both are done. Resistance remains uncommon but is rising in some Trichomonas strains, which is why follow-up matters if symptoms persist.⁶
For anaerobic bacterial infections such as dental or abdominal abscesses it is a long-standing first-line agent, usually alongside drainage of the infected area rather than on its own. Across all of these uses the pattern is the same: it works well when the organism is one it targets and does nothing when it is not, so an accurate diagnosis is what decides the outcome.
90–95%
Trichomoniasis cure
with both partners treated
≈90%
Amoebic infection clearance
with a completed course
Cure rates drawn from treatment guidelines and controlled studies; both partners must be treated for trichomoniasis. Individual results vary.
04
Side effects & who shouldn't take it
Common side effects
The most common effects are a metallic taste, nausea, headache, and loss of appetite. Urine may turn darker, which is harmless. These are usually mild and settle when the course finishes.
Rare but serious
Prolonged or high-dose use can cause tingling or numbness in the hands and feet (peripheral neuropathy). Very rarely there are seizures or confusion. Stop the medicine and seek care if these appear.
The alcohol rule
Do not drink alcohol while taking metronidazole or for 48 hours after your last dose. The combination can trigger a disulfiram-like reaction: flushing, a throbbing headache, nausea, vomiting, and a racing heart. Watch for hidden alcohol in some tonics, cough syrups, and mouthwashes.
Not suitable for & interactions
Tell your doctor if you are in the first trimester of pregnancy, breastfeeding, or have liver disease or a nerve disorder. Metronidazole can boost the effect of blood thinners such as warfarin and interacts with lithium and phenytoin, so list every medicine you take.
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Alternatives & combinations
Oral · closely related
Tinidazole
A related nitroimidazole with similar uses in trichomoniasis, amoebiasis, and giardiasis, sometimes given as a shorter course and slightly better tolerated. The same alcohol rule applies.
Combination · H. pylori
Part of triple therapy
For a stomach H. pylori infection, metronidazole is combined with a proton-pump inhibitor and other antibiotics. It is not used on its own for this.
Alternative · protozoa
Nitazoxanide
An alternative antiparasitic option for giardiasis when a nitroimidazole is not tolerated. A doctor selects the drug based on the organism confirmed by testing.
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How prescription works at Menscape
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A few minutes on your phone: your symptoms, history, current medicines, and any test results. It is PDPA-protected.
Doctor consultation
A licensed Thai physician reviews your case by video call or in clinic at Asoke, and may order or confirm testing to identify the exact infection.
Prescription, if suitable
If treatment is appropriate, you receive the right drug and course length. It is dispensed by a licensed pharmacy for pickup or delivery.
Follow-up & monitoring
A check that symptoms have cleared, a retest where needed (especially for an STI), and advice on treating your partner to prevent reinfection.
The doctor decides. Starting a conversation is not a commitment and does not guarantee a prescription. Diagnosing an infection may require testing first, and if metronidazole is not right for you the doctor will explain what is.
Medically reviewed by
Dr. Noppon Arunkajohnsak (Win)
Menscape Clinic, Bangkok
“Metronidazole is excellent for the infections it targets and useless for the ones it doesn't. The two mistakes I see most are self-treating without a diagnosis and drinking on it. Get the infection identified first.”
- Reviewed
- 11 July 2026
- Next review
- January 2027
- Editorial standard
- Each guide is checked against the Thai FDA label and the primary literature, then reviewed by a licensed physician.
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Frequently asked questions
Can I buy metronidazole over the counter in Thailand?
No. It is a dangerous drug (ยาอันตราย) that must be dispensed by a licensed pharmacist or prescribed by a doctor. Buying it without oversight risks the wrong diagnosis and counterfeit tablets, and it is not legal to sell without a licence.
Why can't I drink alcohol with metronidazole?
Alcohol can trigger a disulfiram-like reaction: flushing, a throbbing headache, nausea, vomiting, and a fast heartbeat. Avoid all alcohol while taking it and for 48 hours after your last dose, including hidden sources like some cough syrups and mouthwashes.
What infections does metronidazole treat?
It treats anaerobic bacterial infections (such as dental and abdominal abscesses) and protozoal infections including trichomoniasis, amoebiasis, and giardiasis, plus H. pylori as part of a combination. It does not treat colds, flu, or ordinary urinary infections.
I think I have trichomoniasis. Does my partner need treatment too?
Yes. Both partners should be treated at the same time even if one has no symptoms, otherwise the infection passes back and forth. Avoid sex until the course is finished and symptoms have gone.
How long until it works?
Symptoms often start improving within a few days. Complete the full course anyway, because stopping early can let the infection return and encourage resistance.
I picked up a stomach bug travelling in Thailand. Is metronidazole the answer?
It is commonly used for amoebic and giardia gut infections once they are diagnosed. Not all traveller's diarrhoea is protozoal, so a doctor should confirm the cause, sometimes with a stool test, before prescribing.
What are the most common side effects?
A metallic taste, nausea, and headache are the usual ones, and urine can look darker, which is harmless. They are generally mild and stop when the course ends.
Can I take it while pregnant or breastfeeding?
Tell your doctor first. Caution is advised especially in the first trimester, and there are timing considerations while breastfeeding. Your doctor will weigh the infection against the safest option for you.
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References
1. U.S. FDA. Flagyl® (metronidazole) prescribing information. Accessed July 2026.
2. Thai Food and Drug Administration — drug registration database, ndi.fda.moph.go.th. Accessed July 2026.
3. Pharmacy Council of Thailand, Notification No. 56/2563 on telepharmacy standards.
4. Thai FDA consumer warnings on purchasing medicines from unlicensed online sellers, oryor.com.
5. CDC. Sexually Transmitted Infections Treatment Guidelines — Trichomoniasis. 2021.
6. Löfmark S, Edlund C, Nord CE. Metronidazole is still the drug of choice for treatment of anaerobic infections. Clin Infect Dis. 2010;50(S1):S16-S23.
7. World Health Organization. WHO Model List of Essential Medicines, 23rd edition. 2023.
This guide is educational information, not medical advice. Metronidazole is a prescription antibiotic that must be prescribed and monitored by a licensed physician. Complete the full course and never share antibiotics.
This guide is part of the Menscape infection library
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