Gout · Medication Guide
Allopurinol in Thailand
What allopurinol is, how it lowers uric acid to control gout long-term, its side effects, and why Thai and Han Chinese patients need a genetic test before starting. Reviewed by a licensed physician at a MOPH-registered men's health clinic.
- For chronic gout, not flares
- HLA-B*5801 gene check first
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Medically reviewed by Dr. Noppon Arunkajohnsak (Win)
Menscape Clinic
Last reviewed
11 July 2026
~9%
Thais carry the risk gene
HLA-B*5801, linked to severe skin reactions
<6
Serum urate target (mg/dL)
the treat-to-target goal in guidelines
100 mg
Typical starting dose
titrated up slowly to lower risk
1966
First approved for gout
decades of clinical use worldwide
Key takeaways
Allopurinol is the first-line long-term medicine for gout: it lowers uric acid so crystals dissolve and attacks become less frequent over time. It is not a painkiller for an active flare.
In Thai and Han Chinese people, a gene called HLA-B*5801 sharply raises the risk of a rare but life-threatening skin reaction. Guidelines recommend a genetic test before you start.
In Thailand it is a prescription medicine (dangerous drug class). It should be started and monitored by a doctor, never self-prescribed from grey-market sellers.
Never start allopurinol during a gout attack, and expect more flares in the first months; a doctor co-prescribes flare cover and titrates the dose to a target urate level.
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What allopurinol is & how it works
Allopurinol is an oral prescription medicine that lowers the level of uric acid in the blood. It is the most widely used long-term treatment for gout, a form of arthritis caused by sharp urate crystals building up in the joints.
It works at the source. Uric acid is produced when the body breaks down purines, using an enzyme called xanthine oxidase. Allopurinol blocks that enzyme, so the body makes less uric acid. When blood urate stays below its saturation point, around 6 mg/dL, existing crystals slowly dissolve and new ones stop forming.
It is a preventive medicine, not a painkiller. It does nothing for the pain of an attack already under way, and starting it mid-flare can make things worse. Its job is to stop future attacks, and it only works for as long as you take it.
Purines break down
The body turns purines, from food and its own cells, into uric acid using the enzyme xanthine oxidase.
Urate builds up
When uric acid rises past its saturation point, it forms sharp crystals in joints, triggering gout attacks and tophi.
Allopurinol blocks the enzyme
A daily tablet inhibits xanthine oxidase, cutting how much uric acid the body produces.¹
Crystals dissolve
Held below about 6 mg/dL, urate crystals gradually dissolve and flares become less frequent over months.²
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Getting allopurinol in Thailand
Thai FDA status
Registered with the Thai FDA and classified as a dangerous drug (ยาอันตราย). It is a standard hospital medicine for gout, sold under brands such as Zyloric alongside registered generics.⁶
How to get it through Menscape
Menscape does not keep allopurinol on the shelf. After a consultation, if a doctor decides it is right for you, it is ordered in for you and dispensed through a licensed pharmacy, with the HLA-B*5801 test arranged before you start.
Safety vs the grey market
Buying allopurinol from unlicensed online sellers means no genetic screening, no dose titration and no monitoring, the three things that make it safe. Counterfeit products are also common. The consult-first route exists to catch risk before the first tablet.
Thai FDA warning. The regulator warns against buying prescription medicines from unlicensed online sellers. With allopurinol, self-medicating without HLA-B*5801 screening and monitoring carries a real risk of severe skin reactions.⁶
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Does it work? The evidence
Allopurinol is the first-line urate-lowering therapy recommended by the American College of Rheumatology and by European guidelines. The approach is treat-to-target: lower blood uric acid and hold it below about 6 mg/dL. At that level, crystals dissolve, attacks become less frequent, and tophi shrink over months to years.²
Dose matters more than most people expect. In a large randomised trial, a fixed 300 mg dose brought only around 42% of patients to target, which is why guidelines now start at 100 mg and titrate the dose up until the target is reached, often 300 to 600 mg. Benefit builds gradually, and the first months can actually bring more flares as old crystals mobilise, so doctors co-prescribe flare cover when starting.⁵
<6 mg/dL
Treat-to-target goal
crystals dissolve when urate is held below this
~42%
Reached target on 300 mg
fixed low dose; titration achieves more
CONFIRMS randomised trial (fixed-dose allopurinol) and ACR 2020 gout guideline. Individual results and required dose vary.
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Side effects & who shouldn't take it
Common side effects
Skin rash is the most common, along with nausea, stomach upset, drowsiness and mildly raised liver enzymes. More gout flares are common in the first few months as urate levels fall, and are expected rather than a sign of failure.¹
Serious, rare reactions
Rarely, allopurinol triggers a severe hypersensitivity syndrome or a severe skin reaction (SJS/TEN, DRESS) that can be life-threatening. These are strongly linked to the HLA-B*5801 gene. Stop the medicine and seek care immediately if you develop a rash, fever or blistering.³
Not suitable / use with care
Do not start it during an acute gout attack. The dose must be reduced in kidney impairment, and asymptomatic high urate without gout is usually not treated with it. Testing for HLA-B*5801 is recommended before starting in Thai, Han Chinese and other higher-risk groups.²
Interactions to flag
Allopurinol dangerously raises levels of azathioprine and mercaptopurine and must be combined with them only under specialist care. It can also increase the effect of warfarin and the rash risk with ampicillin or amoxicillin. Tell your doctor every medicine you take.¹
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Alternatives & combinations
Oral · alternative
Febuxostat
Another xanthine oxidase inhibitor that lowers urate, used when allopurinol is not tolerated or does not reach target. A doctor weighs its own cautions, including cardiovascular history.
Flare cover · often combined
Colchicine
Low-dose colchicine, or an NSAID, is commonly prescribed alongside allopurinol for the first months to prevent the mobilisation flares that come as crystals dissolve.
Supportive care
Diet & lifestyle
Cutting back on alcohol (especially beer), sugary drinks and high-purine foods, plus weight management, supports treatment but does not replace medication in established gout.
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How prescription works at Menscape
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Doctor review & gene screening
A licensed Thai physician reviews your case by video or in clinic at Asoke, and arranges blood tests for uric acid, kidney function and the HLA-B*5801 gene before any medicine is started.
Prescription, if suitable
If screening is clear and allopurinol is right for you, it is started at a low dose with flare cover, ordered in and dispensed through a licensed pharmacy.
Follow-up & monitoring
Repeat blood tests check whether you are reaching the urate target, the dose is titrated accordingly, and the doctor watches for rash, liver and kidney effects.
The doctor decides. Starting a conversation is not a commitment and does not guarantee a prescription. Allopurinol is started only after screening, and only if a doctor judges it right for you.
Medically reviewed by
Dr. Noppon Arunkajohnsak (Win)
Menscape Clinic, Bangkok
“The two mistakes I see most are men starting allopurinol during an attack and buying it online without the HLA-B*5801 gene test. Done properly, with screening first and the dose titrated to target, it is one of the most effective long-term gout treatments we have.”
- 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 allopurinol over the counter in Thailand?
No. It is a prescription medicine in the dangerous drug class. Because of the risk of a severe skin reaction, it should only be started after a doctor's assessment and, for Thai and Han Chinese patients, a genetic test. Grey-market sellers skip both.
What is the HLA-B*5801 test and do I need it?
HLA-B*5801 is a gene variant carried by roughly 9% of Thai and Han Chinese people. Carriers have a far higher risk of an allopurinol-triggered severe skin reaction (SJS/TEN). Guidelines recommend testing before starting in these populations, and Menscape arranges it as part of the consult.
Can I take allopurinol during a gout attack?
No, you should not start it during an attack, as it can prolong or worsen the flare. Doctors wait until the attack has settled, then begin at a low dose with flare cover. If you already take it, you usually keep going through a flare rather than stopping.
Will I have to take it forever?
Gout is usually a lifelong condition, and allopurinol works only while you take it. If you stop, uric acid rises again and attacks return, so it is generally taken long-term with periodic monitoring.
Why am I getting more attacks after starting?
Early flares are common and expected: as urate levels drop, older crystals mobilise. This is temporary and does not mean the medicine is failing, which is why doctors co-prescribe colchicine or an NSAID for the first months.
Is allopurinol safe for my kidneys?
Allopurinol is cleared by the kidneys, so the dose is adjusted when kidney function is reduced. It is often used in people with kidney disease, but with lower starting doses and closer monitoring.
What should I do if I develop a rash?
Stop the medicine and seek medical care immediately, especially in the first weeks. A rash can be the first sign of a serious hypersensitivity reaction, and early action matters.
I already take allopurinol abroad. Can I continue it in Thailand?
Yes. A local doctor can review your treatment, check your urate level and kidney function, and continue your prescription. If you tolerate it well already, your doctor will advise whether further testing is needed.
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References
1. U.S. FDA. Zyloprim® (allopurinol) prescribing information. Accessed July 2026.
2. FitzGerald JD, et al. 2020 American College of Rheumatology Guideline for the Management of Gout. Arthritis Care Res. 2020;72(6):744-760.
3. Hung SI, et al. HLA-B*5801 allele as a genetic marker for severe cutaneous adverse reactions caused by allopurinol. Proc Natl Acad Sci USA. 2005;102(11):4134-4139.
4. Ko TM, et al. Use of HLA-B*58:01 genotyping to prevent allopurinol-induced severe cutaneous adverse reactions in Taiwan: national prospective cohort study. BMJ. 2015;351:h4848.
5. Becker MA, et al. The urate-lowering efficacy and safety of febuxostat and allopurinol in gout (CONFIRMS trial). Arthritis Res Ther. 2010;12(2):R63.
6. Thai Food and Drug Administration — drug registration database, ndi.fda.moph.go.th. Accessed July 2026.
7. Saokaew S, et al. Cost-effectiveness of HLA-B*5801 testing to prevent allopurinol-induced SJS/TEN in Thailand. PLoS One. 2014;9(4):e94294.
This guide is educational information, not medical advice. Allopurinol is a prescription medicine that must be prescribed and monitored by a licensed physician, and should not be started during an acute gout attack.
This guide is part of the Menscape gout library
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