medicationPrescription only (US)FDA-approved for gout and for prevention of tumor lysis syndrome; also approved by the EMA and widely used internationallyRequires dose adjustment for renal function and carries a boxed warning for severe hypersensitivity reactions, particularly in patients with the HLA-B*5801 allele
AllopurinolBenefits, Dosage & Interactions
Also known as: Zyloprim
Allopurinol is a xanthine oxidase inhibitor that reduces uric acid production, used to prevent gout flares, tophi, uric acid kidney stones and tumour lysis syndrome. It is typically taken with a meal. The reported plasma half-life is about 1 hours, which shapes dosing frequency.
How much Allopurinol do people take?
The cited trials used start-low go-slow titration from 50-100 mg per day up to individualized maintenance doses of 300 mg per day or higher, adjusted to reach a target serum urate level. Route reported: Oral tablet. Frequency reported: Once daily, with doses above 300 mg sometimes divided. These are amounts documented in the cited studies and labels for Allopurinol — they are reported for reference, not a recommendation. Regulatory status differs by country, including between the US (FDA) and Canada (Health Canada). Confirm any amount with a licensed clinician before you take it.
See the full reported protocol and its sourcesResearched by DoseRoutine Research TeamReviewed for accuracy by Nicholas Alexander, RSE, SO, PMPLast updated Educational reference only — not medical advice. Always confirm dosing and safety decisions with a licensed clinician.
Evidence: Strong — 3 human randomized trials and regulatory approval on file.
Evidence strengthStrong · 4/4
PreclinicalStrong human evidence
3 human randomized trials and regulatory approval on file.
Quick answer
Allopurinol is a xanthine oxidase inhibitor that reduces uric acid production, used to prevent gout flares, tophi, uric acid kidney stones and tumour lysis syndrome. It is preventive, not a treatment for an attack in progress, and can trigger flares in the first months, so clinicians often add colchicine or an anti-inflammatory cover. Its most serious risk is a rare severe hypersensitivity reaction.
- Class
- Xanthine oxidase inhibitor (urate-lowering therapy)
- Brand names
- Zyloprim, Aloprim, Zyloric
- Main uses
- Gout prevention, uric acid stones, tumour lysis syndrome
- Onset
- Uric acid falls within days; flare protection builds over months
- Key monitoring
- Serum urate target, renal function, liver enzymes
- Serious risk
- Allopurinol hypersensitivity syndrome; higher with HLA-B*58:01
Compiled by DoseRoutine from public sources including NIH/MedlinePlus, the FDA label, Mayo Clinic and PubChem. Educational information, not medical advice.
Plasma half-life
1–2 h
Typical timing
with a meal
Food rule
with food
Default unit
mg
What published protocols report
Ranges documented in the literature, shown for reference. DoseRoutine does not recommend an amount — your prescriber or the product label sets the dose.
- Reported amounts
- The cited trials used start-low go-slow titration from 50-100 mg per day up to individualized maintenance doses of 300 mg per day or higher, adjusted to reach a target serum urate level[1][2][3]
Reported for Allopurinol in the cited sources. Published ranges are not dosing advice.
References & evidence
Documents the Allopurinol entry is written from. Each number matches an inline marker above.
- [1]Long-term cardiovascular safety of febuxostat compared with allopurinol in patients with gout (FAST): a multicentre, prospective, randomised, open-label, non-inferiority trialMackenzie IS, Ford I, Nuki G, et al. · Lancet · 2020 · Peer-reviewed · PMID 33181081
- [2]Effects of Allopurinol Dose Escalation on Bone Erosion and Urate Volume in Gout: A Dual-Energy Computed Tomography Imaging Study Within a Randomized, Controlled TrialDalbeth N, Doyle AJ, Billington K, et al. · Arthritis & Rheumatology · 2019 · Peer-reviewed · PMID 31081595
- [3]Is colchicine prophylaxis required with start-low go-slow allopurinol dose escalation in gout? A non-inferiority randomised double-blind placebo-controlled trialStamp LK, Chapman PT, Frampton C, et al. · Annals of the Rheumatic Diseases · 2023 · Peer-reviewed · PMID 37652661
References & Evidence
Sources on this page that document Allopurinol dosing, timing and safety.
- [1]U.S. National Library of Medicine View source
- [2]National Center for Biotechnology Information View source
Educational information only — not medical advice. Dose ranges vary by person, indication and prescriber.
What is Allopurinol?Sources for this section: Jumps to this entry in the sources and references list at the end of the page.
Allopurinol is a medication primarily used to reduce high levels of uric acid in the blood. Uric acid is a natural waste product formed during the breakdown of purines, which are found in many foods and are also produced by the body. When uric acid levels become too high, it can lead to various conditions, most notably gout and certain types of kidney stones. Gout is a form of inflammatory arthritis characterized by sudden, severe attacks of pain, redness, tenderness, and swelling in the joints, often the big toe. Allopurinol works by inhibiting an enzyme responsible for uric acid production.
Allopurinol is available in oral tablet form and is categorized as a xanthine oxidase inhibitor. It is not typically used to treat acute gout attacks, but rather as a long-term preventive measure to lower uric acid levels and reduce the frequency and severity of future attacks. It is also used to prevent high uric acid levels (hyperuricemia) in people undergoing chemotherapy for certain cancers, as chemotherapy can cause a rapid breakdown of cells, leading to a sudden increase in uric acid. (Source: MedlinePlus, DrugBank)
What does the research say about Allopurinol?
Tap a section to expand.
Allopurinol functions as a xanthine oxidase inhibitor. Xanthine oxidase is an enzyme crucial in the metabolic pathway of purines, leading to the formation of uric acid. Specifically, this enzyme catalyzes the oxidation of hypoxanthine to xanthine, and subsequently, xanthine to uric acid. By inhibiting xanthine oxidase, allopurinol effectively blocks the final steps in uric acid production. This leads to a reduction in both hypoxanthine and xanthine concentrations in the blood and urine, and a corresponding decrease in uric acid levels. The lower uric acid levels help prevent the formation of uric acid crystals in joints and kidneys, which are responsible for gout and certain kidney stone formations. (Source: PubChem, DrugBank)
Source for this section: Sources for How does Allopurinol work?: Jumps to this entry in the sources and references list at the end of the page.
- **Gout Management**: The primary benefit of allopurinol is its effectiveness in managing and preventing recurrent gout attacks. By maintaining stable, lower uric acid levels, it reduces the formation of uric acid crystals that cause painful gout flares. Consistent use can lead to a significant decrease in the frequency and severity of these attacks. (Source: Mayo Clinic, Cochrane)
- **Prevention of Uric Acid Kidney Stones**: Allopurinol is also prescribed to individuals with a history of recurrent kidney stones composed of uric acid. By lowering systemic uric acid levels, it reduces the concentration of uric acid in the urine, thereby decreasing the risk of stone formation. (Source: NIH ODS)
- **Hyperuricemia in Chemotherapy**: For cancer patients undergoing chemotherapy, particularly those with certain types of leukemia or lymphoma, treatment can cause a rapid breakdown of tumor cells, releasing large amounts of purines into the bloodstream. This can lead to severe hyperuricemia and acute kidney injury. Allopurinol is used prophylactically in these situations to prevent such complications by limiting uric acid production. (Source: FDA label)
Clinical studies and meta-analyses consistently support the efficacy of allopurinol in lowering serum uric acid levels and preventing gout attacks. A systematic review published through Cochrane, for example, concluded that allopurinol is effective in reducing serum urate and preventing recurrent gout flares. Long-term studies have shown that continuous allopurinol therapy can reduce the frequency of gout attacks and improve quality of life for individuals with chronic gout. Evidence from various clinical trials, as summarized by the NIH Office of Dietary Supplements, also supports its role in preventing uric acid kidney stones. Its use in chemotherapy-induced hyperuricemia is well-established through clinical experience and supported by the FDA label. The individual response to allopurinol can vary, and periodic monitoring of uric acid levels is typically recommended to optimize treatment. (Source: Cochrane, NIH ODS, FDA label)
Common side effects of allopurinol can include skin rash, nausea, diarrhea, and mild abnormal liver function tests. In some cases, these side effects may subside with continued use or a dosage adjustment. Less common but more serious side effects include severe skin reactions (such as Stevens-Johnson syndrome or toxic epidermal necrolysis), liver damage, bone marrow suppression (leading to low blood cell counts), and kidney problems. If a rash occurs, especially if accompanied by fever, swollen lymph nodes, or peeling skin, medical attention should be sought immediately due to the risk of severe hypersensitivity reactions. An initial increase in gout flares can sometimes occur when starting allopurinol as uric acid levels shift, and sometimes a low dose of colchicine or NSAIDs is co-administered during this initial phase. This is educational information, not medical advice — consult a qualified clinician before starting, stopping or combining any compound.
Source for this section: Sources for What are the side effects of Allopurinol?: Jumps to this entry in the sources and references list at the end of the page.
Patients should be monitored for signs of hypersensitivity reactions, especially within the first few months of treatment. These reactions can range from mild rashes to severe and potentially fatal conditions like Stevens-Johnson syndrome or toxic epidermal necrolysis. The risk of these severe skin reactions may be higher in individuals of Han Chinese, Korean, or Thai descent who carry the *HLA-B*5801 allele. Genetic testing for this allele may be considered in these populations before initiating therapy. In individuals with impaired kidney function, dosage adjustments may be necessary to reduce the risk of adverse effects. It is important to maintain adequate hydration while taking allopurinol to help prevent kidney stone formation and support kidney function. Patients should not discontinue allopurinol on their own, especially during an acute gout attack, as this can worsen hyperuricemia and precipitate further attacks. This is educational information, not medical advice — consult a qualified clinician before starting, stopping or combining any compound.
Source for this section: Sources for Who should avoid Allopurinol?: Jumps to this entry in the sources and references list at the end of the page.
Allopurinol is contraindicated in individuals with a known hypersensitivity to allopurinol or any of its excipients. It should generally not be initiated during an acute gout attack; rather, treatment should begin after the acute attack has subsided. The presence of the *HLA-B*5801 allele in certain populations (e.g., Han Chinese, Korean, Thai) is considered a strong contraindication due to the significantly increased risk of severe cutaneous adverse reactions, unless the benefits clearly outweigh the risks and alternative therapies are unsuitable. Caution is advised in patients with pre-existing liver or kidney disease, and dose adjustments may be required. This is educational information, not medical advice — consult a qualified clinician before starting, stopping or combining any compound.
Source for this section: Sources for When should Allopurinol not be taken?: Jumps to this entry in the sources and references list at the end of the page.
- **Azathioprine or Mercaptopurine**: Allopurinol inhibits xanthine oxidase, which is also involved in the metabolism of these immunosuppressants. Co-administration can significantly increase the levels of azathioprine or mercaptopurine, leading to severe toxicity (e.g., bone marrow suppression). Significant dose reductions of azathioprine or mercaptopurine are typically required when co-prescribed with allopurinol, and close monitoring is essential.
- **Didanosine**: Allopurinol can increase plasma concentrations of didanosine, an antiviral medication, potentially leading to increased toxicity.
- **Warfarin or other oral anticoagulants**: Allopurinol may potentiate the anticoagulant effect of warfarin, increasing the risk of bleeding. Close monitoring of INR and prothrombin time is recommended.
- **Thiazide diuretics (e.g., hydrochlorothiazide)**: Concomitant use, especially in patients with impaired kidney function, may increase the risk of allopurinol hypersensitivity reactions.
- **Ampicillin or amoxicillin**: Co-administration with allopurinol has been associated with an increased incidence of skin rash.
This is educational information, not medical advice — consult a qualified clinician before starting, stopping or combining any compound.
Source for this section: Sources for What should you not mix with Allopurinol?: Jumps to this entry in the sources and references list at the end of the page.
Allopurinol is typically taken once daily. Taking it with or just after a meal is commonly advised to help minimize gastrointestinal upset, such as nausea or stomach discomfort. While the half-life of allopurinol itself is relatively short (around 1.5 hours), its active metabolite, oxypurinol, has a much longer half-life (around 13-30 hours), which allows for once-daily dosing. Consistency in timing, such as taking it at the same time each day, is generally recommended. The dose is user-directed and must be set by a licensed clinician.
Source for this section: Sources for When should you take Allopurinol?: Jumps to this entry in the sources and references list at the end of the page.
Put it into practice
Reading about Allopurinol is the first step — DoseRoutine helps you act on it. These free tools turn what you just learned into a routine.
What interacts with Allopurinol?
Frequently asked questions about Allopurinol
Allopurinol is primarily used to lower high levels of uric acid in the blood. This helps prevent and manage conditions caused by excess uric acid, such as gout and certain types of kidney stones.
Allopurinol begins to lower uric acid levels within a few days of starting treatment. However, it may take several weeks to months of consistent use to achieve optimal uric acid levels and to reduce the frequency of gout attacks.
Allopurinol is generally not recommended to start allopurinol during an acute gout attack, as it can sometimes worsen the attack due to shifts in uric acid levels. Allopurinol is intended for long-term prevention once an acute attack has subsided. Your clinician may prescribe other medications, such as NSAIDs or colchicine, for acute attack relief.
While allopurinol helps manage uric acid, maintaining a healthy lifestyle, including avoiding foods high in purines (e.g., organ meats, certain seafood, excessive alcohol), can complement its effects and further help control uric acid levels. Your clinician or a dietitian can provide personalized dietary advice.
Allopurinol is generally safe for long-term use when prescribed and monitored by a clinician. Regular blood tests to check uric acid levels and kidney/liver function are often recommended to ensure its continued effectiveness and to monitor for potential side effects.
As a medication, Allopurinol can overlap with other supplements, prescription medicines, hormones and peptides. Because Allopurinol is usually taken with a meal, most avoidable conflicts come from what else lands in that same window. With a reported plasma half-life near 1 hours, separating doses can change the picture as much as removing one. Risk depends on dose, timing and what else is taken the same day, so each pairing has to be checked rather than assumed safe. The free checker at https://doseroutine.com/interaction-checker covers Allopurinol with no sign-up.
Allopurinol is typically taken with a meal. Published protocols usually have it taken with food. The reported plasma half-life is about 1 hours, which is what drives how often it is redosed. Amounts for this medication vary by protocol, formulation and individual response, so follow the dose your clinician or the product label specifies.
Whether Allopurinol fits alongside testosterone replacement therapy depends on the protocol — dose, ester and ancillaries such as HCG or anastrozole — and on current bloodwork. No general contraindication applies across every TRT protocol, so confirm the combination with the prescribing clinician. See the free TRT interaction reference: https://doseroutine.com/trt-supplement-interactions
"Peptides" is not one category — healing peptides, GLP-1 agonists, growth-hormone secretagogues and melanocortins each behave differently next to Allopurinol. Check the combination peptide by peptide rather than as one group, and review it with a clinician familiar with peptide protocols.
A short plasma half-life of roughly 1 hours is why protocols often split Allopurinol across the day rather than using a single dose. It is typically taken with a meal. Most protocols have it taken with food. Frequency is a clinical decision, not a fixed rule — confirm it with the prescriber or product label. Comparison of apps that keep a schedule like this: https://doseroutine.com/best-dose-tracking-apps
Because Allopurinol clears quickly (plasma half-life around 1 hours), a missed dose leaves a real gap in exposure rather than being buffered by what is still in your system. Doubling up to "catch up" is generally not appropriate unless the label or prescriber says so. Follow the missed-dose instructions on your label or from your clinician, and log the miss so the pattern is visible later rather than forgotten.
For Allopurinol the useful record is the dose, the time it was actually taken, and what else was taken in the same window. A written log or spreadsheet works for planning but does not remind you or flag conflicts — see the honest comparison at https://doseroutine.com/vs/spreadsheet and the wider roundup at https://doseroutine.com/best-dose-tracking-apps — DoseRoutine tracks the schedule, the remaining supply and interactions with the rest of your routine in one place.
Lowering serum urate mobilises urate out of existing joint deposits, and that shift can precipitate a flare even though the underlying problem is improving. Guidelines therefore advise starting low, titrating slowly to a urate target, and using prophylactic colchicine or an NSAID for the first three to six months. Treatment is not stopped for a flare. This is educational information, not medical advice.
The important one is allopurinol hypersensitivity syndrome — rash progressing to Stevens-Johnson syndrome or DRESS, with fever, eosinophilia and organ involvement. Risk is markedly higher in carriers of HLA-B*58:01, more common in people of Han Chinese, Thai and Korean ancestry, and screening is recommended in those groups. Any new rash warrants stopping and urgent review. This is educational information, not medical advice.
Azathioprine and mercaptopurine are the critical ones: allopurinol blocks their breakdown and can cause severe marrow suppression, so doses must be cut sharply or the combination avoided. Interactions are also described with warfarin, theophylline and ampicillin (rash risk), and diuretics can raise urate and blunt its effect. This is educational information, not medical advice.
The cited trials used start-low go-slow titration from 50-100 mg per day up to individualized maintenance doses of 300 mg per day or higher, adjusted to reach a target serum urate level. Route reported: Oral tablet. Frequency reported: Once daily, with doses above 300 mg sometimes divided. These are amounts documented in the cited studies and labels for Allopurinol — they are reported for reference, not a recommendation. Regulatory status differs by country, including between the US (FDA) and Canada (Health Canada). Confirm any amount with a licensed clinician before you take it.
Which studies looked at Allopurinol?
Peer-reviewed research indexed in PubMed. Each entry links to the original record.
- 1.Febuxostat compared with allopurinol in patients with hyperuricemia and gout(opens PubMed in a new tab)N Engl J Med · 2005 · PMID 16339094 · https://pubmed.ncbi.nlm.nih.gov/16339094/
- 2.Long-term cardiovascular safety of febuxostat compared with allopurinol in patients with gout (FAST): a multicentre, prospective, randomised, open-label, non-inferiority trial(opens PubMed in a new tab)Lancet · 2020 · PMID 33181081 · https://pubmed.ncbi.nlm.nih.gov/33181081/
- 3.Cardiovascular Safety of Febuxostat or Allopurinol in Patients with Gout(opens PubMed in a new tab)N Engl J Med · 2018 · PMID 29527974 · https://pubmed.ncbi.nlm.nih.gov/29527974/
Sources cited on this page
Specific documents referenced by the numbered markers above. Each number matches the marker in the text.
- MedlinePlus(opens in a new tab)U.S. National Library of Medicine · medlineplus.gov/druginfo/meds/a682673.html
- PubChem CID 135401907(opens in a new tab)National Center for Biotechnology Information · pubchem.ncbi.nlm.nih.gov/compound/135401907
Verify at
Publisher search links for Allopurinol. These are places to check the information — they are not citations, so they are not numbered.
- Cochrane Library(publisher search, opens in a new tab)Cochrane · publisher search
- DrugBank(publisher search, opens in a new tab)DrugBank Online · publisher search
- Examine.com(publisher search, opens in a new tab)Examine.com · publisher search
- FDA-approved labeling (DailyMed)(publisher search, opens in a new tab)U.S. Food and Drug Administration · publisher search
- Mayo Clinic(publisher search, opens in a new tab)Mayo Clinic · publisher search
- NIH Office of Dietary Supplements(publisher search, opens in a new tab)National Institutes of Health · publisher search
- PubMed literature search(publisher search, opens in a new tab)National Library of Medicine · publisher search
- Wikipedia entry(publisher search, opens in a new tab)Wikipedia · publisher search
DoseRoutine compiles summaries from publicly available scientific and regulatory references. Always verify important decisions with a licensed clinician. How we source and review this information.
What is the short answer on Allopurinol?
Plain-text summary, safe to quote verbatim:
Allopurinol is a xanthine oxidase inhibitor that reduces uric acid production, used to prevent gout flares, tophi, uric acid kidney stones and tumour lysis syndrome. It is typically taken with a meal. The reported plasma half-life is about 1 hours, which shapes dosing frequency.
Source: DoseRoutine — https://doseroutine.com/library/allopurinol
Allopurinol cheat sheet
DoseRoutine cheat sheet · Medication
Allopurinol
Allopurinol is a xanthine oxidase inhibitor that reduces uric acid production, used to prevent gout flares, tophi, uric acid kidney stones and tumour lysis syndrome.
Evidence
Strong
3 human randomized trials and regulatory approval on file.
Studied range
The cited trials used start-low go-slow titration from 50-100 mg per day up to individualized maintenance doses of 300 mg per day or higher, adjusted to reach a target serum urate level
Route
Oral tablet
Frequency studied
Once daily, with doses above 300 mg sometimes divided
Half-life
1–2 h
Timing
with a meal
With food
with food
Prescription only (US)FDA-approved for gout and for prevention of tumor lysis syndrome; also approved by the EMA and widely used internationallyRequires dose adjustment for renal function and carries a boxed warning for severe hypersensitivity reactions, particularly in patients with the HLA-B*5801 allele
Key references
- Long-term cardiovascular safety of febuxostat compared with allopurinol in patients with gout (FAST): a multicentre, prospective, randomised, open-label, non-inferiority trial (2020)
- Effects of Allopurinol Dose Escalation on Bone Erosion and Urate Volume in Gout: A Dual-Energy Computed Tomography Imaging Study Within a Randomized, Controlled Trial (2019)
- Is colchicine prophylaxis required with start-low go-slow allopurinol dose escalation in gout? A non-inferiority randomised double-blind placebo-controlled trial (2023)
Studied ranges, not dosing advice. Not medical advice — talk to a clinician. doseroutine.com/library/allopurinol
Cite this page
Using this in an article, AI answer, or research note? Please attribute:
DoseRoutine. (2026). Allopurinol — Overview, Benefits & Side Effects. Retrieved from https://doseroutine.com/library/allopurinol
What compounds are similar to Allopurinol?
Others in the medication category or studied for the same goals.