ALLOPURINOL (Zyloprim): What is used for?

What is allopurinol?

Allopurinol (Alopurinol) is a drug used to treat acute uric acid and gout. The product ingredient is allopurinol sodium.

The brand names of allopurinol in the United States are: Zyloprim, Lopurin, Aloprim.

Mechanism of action (MOA) of Allopurinol

Decreases the level of uric acid in plasma and urine by inhibition of xantinoxidasa, an enzyme that catalyzes the oxidation of hypoxanthine to xanthine and from xanthine to uric acid.

Therapeutic indications, uses and benefits of allopurinol

Treatment of clinical manifestations of uric acid/urate deposition in: idiopathic gout; uric acid lithiasis; acute uric acid nephropathy; neoplastic and myeloproliferative disease with high frequency of cell turnover, in which high levels of urate occur, both spontaneously and after cytotoxic treatment.

Enzyme alterations with urate overproduction: hypoxanthine guanine phosphoribosyltransferase, including Lesch-Nyhan syndrome; glucose-6-phosphatase including glycogen storage disease.

Phosphoribosylpiprophosphate synthetase; phosphoribosylprophosphate amido-transferase; adenine phosphoribosyltransferase; glutathione reductase; glutamate dehydrogenase.

Treatment of kidney stones of 2,8-dihydroxyadenine, related to deficient activity of adenine phosphoribosyl-transferase.

Recurrent mixed renal lithiasis of calcium oxalate, in the presence of hyperuricosuria, when measures such as diet, fluid intake or other therapeutic measures fail.

Dosage of allopurinol


Adults: slight alterations: 100-200 mg/day.

Moderate alterations: 300- 600 mg/day. Severe alterations: 700-900 mg/day. In the elderly, use the lowest dose that produces a satisfactory reduction in urates.

Children <15 years: 100-400 mg/day (malignant processes and Lesch-Nyhan syndrome).

Kidney failure, starting at 100 mg/day max, severe < 100 mg/day or single doses of 100 mg at intervals > 1 day. In renal dialysis (2-3 times/week): 300-400 mg immediately after each session, and do not administer on days without dialysis.

Liver failure reduce dose.

Contraindications of allopurinol

Hypersensitivity to allopurinol.

In case of treatment for an acute gout attack; prophylactic therapy may be initiated when the acute attack has completely decreased, provided that anti-inflammatory agents are also taken.

Warnings and Cautions with Allopurinol

Liver failure, Kidney failure, patients on treatment for high blood pressure or heart failure. Discontinue in case of hypersensitivity (rash).

Once they have remitted, if necessary, restart treatment at a lower dose (50 mg/day), gradually increasing. In case of relapses, discontinue administration definitively due to the risk of more serious hypersensitivity reactions.

Treatment should not be started until the acute gout attack has passed. An acute attack of gouty arthritis (prophylactic administration of an anti-inflammatory or colchicine) may be precipitated in early stages. Hydrate properly.

Risk of hypersensitivity reactions in various forms including maculopapular exanthema, s. of hypersensitivity (s. Dress) and s. of Stevens Johnson/toxic epidermal necrolysis, if these reactions occur during treatment, treatment should be withdrawn. Resumption of treatment should not be performed in patients with hypersensitivity syndrome.

Liver failure


Caution. Reduce dose. Perform periodic liver function tests during the initial stages of treatment.

Renal failure


Caution. Start at 100 mg/day max, severe < 100 mg/day or single doses of 100 mg at intervals > 1 day.

In renal dialysis (2-3 times/week): 300-400 mg immediately after each session, and do not administer on days when dialysis is not performed.

Interactions with allopurinol

  • Increases action and toxicity of: 6-mercaptopurine, azathioprine, adenine arabinoside, cyclosporine.
  • Increase effects of: theophylline, warfarin and cumarin anticoagulants.
  • Increases frequency of skin rash with: ampicillin/amoxicillin.
  • Effect decreased by: probenecid and high doses of salicylates.
  • Increases plasma Cmax and AUC values: didanosine.



No human experience.

It should only be used when there is no safer alternative and when the disease itself carries risks to the mother or fetus.


Not recommended for use during lactation.

Allopurinol and its metabolites occur in human milk and may cause adverse reactions in infants.

Therefore, its administration during lactation is not recommended.

Effects on driving ability


Since adverse reactions such as drowsiness, vertigo and ataxia have been described in patients treated with alopurinol, patients should not drive, use machinery or engage in hazardous activities until they are reasonably satisfied that their behaviour is not adversely affected.

Adverse reactions or side effects of allopurinol

Rash; increased thyroid stimulating hormone; very rare frequency: agranulocytosis, thrombocytopenia and aplastic anemia, especially in renal and/or hepatic insufficiency.


Source: The content of this active ingredient has been written taking into account the clinical and molecular information of all medicines authorised and marketed in the United States under the Unique Ingredient Identifier (UNII) by the Substance Registration System (SRS) of the Food and Drug Administration (FDA) and the United States Pharmacopeia (USP).

In order to know in detail the information authorized by the FDA for each drug, you should consult the corresponding medication guide authorized by the FDA.


PubChem CID: 2094
NCI Thesaurus: C224

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