Prescription medication · Xanthine Oxidase Inhibitor
allopurinol
Also sold as Zyloprim. This medicine is used to manage gout in adults.
Data updated 2026-05-15
- 150,998
- FDA reportsHeavily reported
- 10
- InteractionsSeveral interactions
- In shortage
- FDA status
What the data shows
allopurinol (Zyloprim) is a prescription Xanthine Oxidase Inhibitor, more reported than roughly 9 in 10 tracked drugs (150,998 FDA reports), with 10 documented drug interactions.
Reporting volume reflects how widely a drug is used and studied, not how dangerous it is, a FAERS report documents a temporal association, never proof of cause.
allopurinol (Zyloprim) is a prescription Xanthine Oxidase Inhibitor. This medicine is used to manage gout in adults.
Allopurinol is a medicine that lowers uric acid levels in your body. It helps prevent gout attacks and other problems caused by high uric acid.
Verify with FDA → · CMS NADAC pricing →
Drug Shortage Alert
allopurinol is currently listed as to be discontinued by the FDA. Affected manufacturer: Teva Pharmaceuticals USA, Inc..
View all drug shortages →Drug Pricing (NADAC)
Generic Price
$0.04/unit
Generic Available
Yes (15 manufacturers)
Pricing data from NADAC (CMS), effective December 18, 2024. Compare all drug costs →
What it does
This medicine is used to manage gout in adults.
Common side effects
Diarrhea, Nausea, Increased liver enzyme levels
Key warnings
Allopurinol can cause serious skin reactions that can be deadly.
The sections below are summarized in plain English from allopurinol's FDA-approved prescribing information. They describe what the official label says, and are not personal medical advice.
How It Works
Allopurinol works by blocking an enzyme called xanthine oxidase. This enzyme helps your body make uric acid. By blocking it, allopurinol reduces the amount of uric acid in your blood and urine.
How to Take It
Take this medicine by mouth, exactly as your doctor tells you. For gout, the starting dose is usually 100 mg each day. Your doctor may increase the dose by 100 mg each week until your uric acid level is below 6 mg/dL. You can take this medicine with or without food.
This is a plain-language summary of allopurinol's FDA labeling, not individualized dosing advice. Ask a pharmacist or prescriber before changing how you take this medication.
Pregnancy & Breastfeeding
Allopurinol may harm your unborn baby. Talk to your doctor if you are pregnant or plan to become pregnant. It is not recommended to breastfeed while taking this medicine because it can pass into breast milk.
This is a plain-language summary of allopurinol's FDA labeling, not individualized advice. Ask a pharmacist or prescriber about pregnancy or breastfeeding on this medication.
Missed Dose
If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and continue with your regular schedule.
This is a plain-language summary of allopurinol's FDA labeling, not individualized advice. Ask a pharmacist or prescriber what to do about your specific missed dose.
Storage
Store at room temperature, away from moisture and heat.
Side Effects (from patient reports)
Based on 150,998 FDA adverse event reports.
Most-reported reactions
Adverse reactions in FAERS for allopurinol, by number of reports
- Diarrhea
Diarrhea
8,423 reports
- Tiredness
Tiredness
7,965 reports
- Difficulty breathing
Difficulty breathing
7,659 reports
- Feeling sick to your stomach
Feeling sick to your stomach
7,061 reports
- Death
Death
6,664 reports
- Sudden kidney damage
Sudden kidney damage
6,554 reports
- Fever
Fever
5,946 reports
- Lung infection
Lung infection
5,568 reports
- Weakness
Weakness
5,484 reports
- Low red blood cell count
Low red blood cell count
5,283 reports
What this shows Bars show how often each reaction was reported, not how likely it is to happen, a report records a temporal association, never proof that the drug caused it.
Reports over time
Adverse-event reports filed for allopurinol each year to the FDA Adverse Event Reporting System (FAERS).
Year-to-year volume tracks usage, prescribing, and scrutiny, not a change in per-patient risk. Source: FDA FAERS.
Where allopurinol sits
allopurinol has more FDA adverse-event reports than 92% of the drugs FAERS tracks. A high position reflects how widely a drug is used and watched, not how dangerous it is.
Percentile across all drugs PlainMeds tracks by FAERS report volume. The dot is allopurinol; the line is the median (50th percentile).
FDA Adverse Event Report Analysis
Detailed analysis of 150,998 reports from the FDA Adverse Event Reporting System (FAERS). Reports span 1997–2025.
Total Reports
150,998
Reports Mentioning Death
21,323
14.1% of reports — not proof of cause
Hospitalization Reports
74,277
Top Indication
Product Used For Unknown Indication
Gender Distribution
Age Distribution
Most Reported Adverse Reactions (FAERS)
| # | Reaction | Reports |
|---|---|---|
| 1 | DIARRHOEA | 8,423 |
| 2 | FATIGUE | 7,965 |
| 3 | DYSPNOEA | 7,658 |
| 4 | NAUSEA | 7,063 |
| 5 | DEATH | 6,665 |
| 6 | ACUTE KIDNEY INJURY | 6,554 |
| 8 | PYREXIA | 5,943 |
| 9 | PNEUMONIA | 5,568 |
| 10 | ASTHENIA | 5,486 |
| 11 | ANAEMIA | 5,285 |
| 13 | DIZZINESS | 4,936 |
| 14 | RENAL FAILURE | 4,688 |
| 15 | FALL | 4,544 |
| 16 | VOMITING | 4,318 |
| 17 | HYPOTENSION | 4,180 |
Reactions in Death Reports
Reactions in Hospitalization Reports
Source: FDA FAERS (Adverse Event Reporting System) FDA FAERS (Adverse Event Reporting System) Reports are voluntary and do not establish causation
Serious Warnings
Allopurinol can cause serious skin reactions that can be deadly. Stop taking this medicine and get medical help right away if you get a skin rash or any other signs of an allergic reaction.
Known Drug Interactions
( 7.2 ) Pegloticase: Discontinue and refrain from initiating treatment with allopurinol tablets. Pegloticase Clinical Impact Concomitant use of allopurinol tablets and pegloticase may potentially blunt the rise of serum uric acid levels and increase the risk of pegloticase related anaphylaxis in patients whose uric acid level increase to above 6 mg/dL. Intervention Discontinue and do not institute allopurinol tablets therapy during treatment with pegloticase.
Mechanism: Allopurinol can hide changes in your blood levels that warn doctors of a possible severe allergic reaction to pegloticase.
What to do: Stop taking allopurinol before starting pegloticase and do not take it again while you are on treatment.
Cyclosporine Clinical Impact Concomitant use of allopurinol increases cyclosporine concentrations, which may increase the risk of adverse reactions. Intervention Increase frequency of monitoring cyclosporine concentrations as reflected in its prescribing information and modify the dosage of cyclosporine as appropriate when used concomitantly with allopurinol tablets.
Mechanism: Allopurinol slows down how your body gets rid of cyclosporine, leading to higher levels of the drug in your system.
What to do: Your doctor should check your blood levels more often and may need to adjust your dose.
( 7.1 ) Concomitant use of Amoxicillin and Clavulanate Potassium and oral anticoagulants may increase the prolongation of prothrombin time.( 7.2 ) Co-administration with allopurinol increases the risk of rash. 7.3 Allopurinol The concurrent administration of allopurinol and amoxicillin increases the incidence of rashes in patients receiving both drugs as compared to patients receiving amoxicillin alone. It is not known whether this potentiation of amoxicillin rashes is due to allopurinol or the hyperuricemia present in these patients.
Mechanism: Taking these two medicines at the same time increases the chance that you will develop a skin rash. It is not fully known if the drugs themselves or the high uric acid levels in the body cause this reaction.
What to do: Watch for any signs of a skin rash and contact your healthcare provider immediately if one appears.
( 7.1 ) Concomitant use of AUGMENTIN and oral anticoagulants may increase the prolongation of prothrombin time.( 7.2 ) Co-administration with allopurinol increases the risk of rash. 7.3 Allopurinol The concurrent administration of allopurinol and amoxicillin increases the incidence of rashes in patients receiving both drugs as compared to patients receiving amoxicillin alone. It is not known whether this potentiation of amoxicillin rashes is due to allopurinol or the hyperuricemia present in these patients.
Mechanism: Taking these two drugs together increases the chance of developing a skin rash. It is not fully known if the rash is caused by the drugs themselves or the medical condition being treated.
What to do: Watch your skin closely for any new rashes and tell your doctor immediately if one appears. Your doctor may need to monitor your reaction to these medications.
Warfarin Clinical Impact Allopurinol may inhibit the metabolism of warfarin, possibly enhancing its anticoagulant effect. Assess INR frequently and adjust warfarin dosage accordingly when allopurinol is added to warfarin therapy.
Mechanism: Allopurinol slows down the body's ability to break down warfarin. This can cause warfarin to stay in the body longer and increase the risk of bleeding.
What to do: Your doctor should check your blood clotting levels (INR) frequently and adjust your warfarin dose if necessary.
This is a plain-language summary of interactions documented in FDA labeling, not individualized advice. Ask a pharmacist or prescriber before combining medications.
Common Questions
Can I stop taking allopurinol when my gout pain is gone?
How long does it take for allopurinol to work?
Can I take allopurinol during a gout attack?
Will allopurinol cure my gout?
Are there any foods I should avoid while taking allopurinol?
Can allopurinol affect my kidneys?
Can allopurinol affect my liver?
Can I drink alcohol while taking allopurinol?
What should I do if I get a rash while taking allopurinol?
Does allopurinol interact with other medications?
What are the common side effects of allopurinol?
Does allopurinol interact with other medications?
What drug class is allopurinol?
Is allopurinol safe during pregnancy?
Is allopurinol currently in shortage?
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Medication Guides
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Narrow Therapeutic Index Drugs
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Common Drug Interactions
Dangerous medication combinations and how to protect yourself
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What the FDA Data Shows for allopurinol
The FDA label for allopurinol (sold under brand names such as Zyloprim) classifies it as a prescription-only medication in the Xanthine Oxidase Inhibitor class. This medicine is used to manage gout in adults. Official labeling lists 5 commonly reported side effects, including Diarrhea, Nausea, Increased liver enzyme levels.
Post-market surveillance from the FDA Adverse Event Reporting System (FAERS) captures real-world experience. For this drug, FAERS contains 150,998 voluntary reports. The database also lists 10 documented drug interactions derived from FDA labeling, with the top-flagged interaction rated major severity. NADAC pricing from CMS shows a generic unit cost of $0.04.
Report counts do not establish causation, a FAERS entry documents a temporal association, not proof that the drug produced the outcome. Widely prescribed medications naturally accumulate more reports than niche therapies, so raw totals must be interpreted alongside total exposure. Shortage status, recall history, and patent information further shape supply and switching decisions. This page summarizes public FDA data for educational purposes only and is not a substitute for professional medical advice, always consult a licensed healthcare provider before starting, stopping, or changing any medication.
Data Sources
Drug labeling: FDA Drug Labels (SPL/DailyMed). Adverse events: FDA Adverse Event Reporting System (FAERS). Pricing: CMS National Average Drug Acquisition Cost (NADAC). Shortage status: FDA Drug Shortages Database.
FAERS reports are voluntary and do not establish causation. Drug interactions are derived from FDA labeling and clinical references. Always consult a healthcare professional before making medication decisions.
Last updated: July 8, 2024
Read our methodology - how this data is sourced, computed, and verified.
Data currency: FDA FAERS adverse-event reports through 2025, CMS NADAC acquisition-cost pricing effective December 2024, compiled and last refreshed May 2026. See our methodology for per-source dates and refresh cadence. Spot a figure that looks wrong? Report a correction.
All federal data sources used on this page
- FDA Orange Book - approved drug products with therapeutic equivalence. accessdata.fda.gov/cder/ob
- FDA DailyMed - NIH-hosted drug labeling for FDA-approved meds. dailymed.nlm.nih.gov
- FDA Adverse Event Reporting System (FAERS) - post-marketing safety surveillance. fda.gov/drugs/faers
- NLM RxNorm - standardized clinical drug nomenclature. nlm.nih.gov/research/umls/rxnorm
- CMS Medicare Part B Drug Average Sales Price Files - federal drug pricing data. cms.gov/medicare/part-b-drugs/asp
- FDA Drug Shortages Database - current and resolved drug shortage tracking. accessdata.fda.gov/drugshortages