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Category: Other
Commercial name: Allopurinol
Active ingredient: Allopurinol
Production form: Pills
Available dosage: 100 mg, 300 mg

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Allopurinol. Dosage, Side Effects, Interactions

Allopurinol is an active ingredient that is used to treat increased uric acid levels in the blood (hyperuricemia) and thus chronic gout. The gout remedy belongs to the active substance class of xanthine oxidase inhibitors and is a uricostatic.


Allopurinol is used to treat:

  • Hyperuricemia with serum uric acid levels in the range of 500 μmol/L (8.5 mg/100 mL) and above
  • Secondary hyperuricemia of various origins

For children, there are the following indications for the use of allopurinol:

  • Secondary hyperuricemia of various genesis
  • Uric acid nephropathy in leukemia treatment
  • Congenital enzyme deficiency diseases Lesch-Nyhan syndrome (partial or total hypoxanthine guanine phosphoribosyl transferase defects) and adenine phosphoribosyl transferase deficiency

Application type

Allopurinol is available on the market in the form of tablets. The tablets are swallowed whole with plenty of liquid after a meal.

How Allopurinol works

Allopurinol and its main metabolite, oxipurinol, inhibit the enzyme xanthine oxidase, which plays an important role in the oxidation of hypoxanthine to uric acid. Inhibition reduces uric acid formation and thus lowers uric acid and urate levels in body fluids and urine. In addition to inhibiting purine degradation, de novo purine biosynthesis can also be suppressed in some patients by inhibiting hypoxanthine-guanine phosphoribosyl transferase.


Allopurinol is rapidly absorbed from the gastrointestinal tract and is detectable in plasma 30 to 60 minutes after oral administration. Peak allopurinol plasma levels are reached one and a half hours after ingestion, whereas allopurinol is hardly detectable in the plasma after about 6 hours. Peak oxipurinol plasma levels are reached about 3 to 5 hours after oral allopurinol ingestion. The most favorable absorption conditions prevail in the duodenum and in the upper jejunum. Maximum serum allopurinol levels at the usual therapeutic dose of 300 mg (depending on the extent and rate of individual first-pass conversion to oxipurinol) average 1.8 μg/ml. The corresponding oxipurinol values ​​average 8.4 μg/ml.

After a single dose of 300 mg allopurinol, plasma peak values ​​averaging 5.24 μg oxypurinol/ml were measured under standardized conditions with volunteers.
Twenty-four hours after a single oral dose of 300 mg allopurinol, the mean concentration of oxipurinol in plasma was 3.78 μg/ml.

Accumulation occurs upon initiation of therapy due to the long half-life of oxipurinol. Equilibrium is reached after about 1 week. The volume of distribution of allopurinol is approximately 1.6 L/kg, suggesting a relatively high level of tissue uptake.

Allopurinol is rapidly oxidized by xanthine oxidase and aldehyde oxidase to oxipurinol (alloxanthine), which is a similar potent inhibitor of xanthine oxidase but binds to the enzyme more slowly.
Neither allopurinol nor its main metabolite, oxypurinol, are tightly bound to plasma proteins. Excretion is predominantly renal, with less than 10% of the drug excreted unchanged. About 20% of the administered allopurinol is found in the faeces after 48 to 72 hours. Oxipurinol is excreted unchanged in the urine after tubular reabsorption.

The elimination half-life of oxipurinol is subject to large individual variations. In healthy people it is between 18 and 43 hours, in some cases up to 70 hours during a purine-free diet. Renal impairment leads to a prolongation of the oxipurinol elimination half-life.

In patients with a creatinine clearance of 10-20 ml/min, after administration of 300 mg allopurinol/day, oxipurinol plasma concentrations were measured over a longer period of time, which roughly correspond to the concentration found in patients after administration of 600 mg allopurinol/day achieved with normal renal function. The absolute bioavailability of 100 and 300 mg allopurinol is between 67 and 90 percent.

Dosage of Allopurinol

Usually between 100 and 300 mg of allopurinol are taken daily. The dosage depends on the measured serum uric acid values.
In individual cases, the dose can be increased to 600 to 800 mg allopurinol daily. A single dose of 300 mg should not be exceeded.


The daily dose is 10 mg allopurinol/kg body weight (up to a maximum of 400 mg/day), divided into 3 individual doses.

Side effects of Allopurinol

Common side effects associated with the use of allopurinol are gastrointestinal problems such as diarrhea, vomiting and nausea. Of the observed side effects, skin reactions are the most common (about 4%). In individual cases, blood count changes such as leukopenia, leukocytosis, granulocytosis and eosinophilia have been reported. The occurrence of side effects is more frequent in the presence of renal and/or hepatic insufficiency or with concomitant ampicillin or amoxicillin therapy, suggesting the need for particularly careful monitoring of this patient group.


  • Probenecid ► Allopurinol slows the elimination of probenecid
  • Drugs that cause increased excretion of uric acid, such as probenecid, benzbromarone , sulfinpyrazone or salicylates in high doses ► The excretion of allopurinol is accelerated by the simultaneous administration of and thus the effectiveness is reduced.
  • 6- mercaptopurine or azathioprine ► Dose must be reduced to 25% of the usual dose, since the metabolism of these active ingredients is slowed down with xanthine oxidase inhibition and their effect is therefore prolonged.
  • Ampicillin or amoxicillin ► Allergic reactions (skin rashes) are more likely to occur when allopurinol is administered at the same time.
  • Captopril ► The risk of skin reactions can be increased, particularly in the case of chronic kidney failure.
  • Coumarin-type anticoagulants ► Effect can be increased. It is therefore necessary to check blood coagulation more frequently and, if necessary, to reduce the dose of the coumarin derivative accordingly.
  • Chlorpropamide ► The hypoglycaemic effect of the antidiabetic chlorpropamide can be prolonged by the simultaneous administration of allopurinol, particularly in the case of impaired renal function, which makes a dose reduction necessary.
  • Theophylline ► In high doses, allopurinol inhibits theophylline metabolism. Theophylline plasma levels should therefore be determined at the start of treatment with allopurinol or when the allopurinol dose is increased.
  • Cytostatics (e.g. cyclophosphamide , doxorubicin , bleomycin , procarbazine , alkyl halides) ► Changes in the blood picture occur more frequently than when the active substances are administered individually.
  • Vidarabine ►the plasma half-life of vidarabine may be prolonged in the presence of allopurinol.
  • Ciclosporin ►The plasma concentration of ciclosporin can be increased under allopurinol administration.
  • Phenytoin ► Allopurinol may interfere with the hepatic metabolism of phenytoin. A clinical significance is not known so far.
  • Didanosine ► Allopurinol, when co-administered, may increase didanosine exposure and thus increase the potential for didanosine-associated side effects, since xanthine oxidase is involved in didanosine metabolism.
  • Aluminum hydroxide ► Allopurinol can have a limited effect when taken at the same time as aluminum hydroxide. There should be at least 3 hours between taking the two medicines.


Hypersensitivity to the active substance


Animal studies have shown reproductive toxicity. Because allopurinol interferes with purine metabolism and the potential risk to humans is unknown, allopurinol should not be used during pregnancy unless clearly necessary.


Allopurinol and its metabolite, oxypurinol, are excreted in breast milk. Allopurinol should not be used while breastfeeding.

Driving ability

Side effects such as drowsiness, dizziness and ataxia can occur during treatment with allopurinol. Patients should therefore exercise caution before driving a motor vehicle, using machines or participating in hazardous activities until they are reasonably certain that allopurinol will not impair their ability to function.

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Additional information


100 mg, 300 mg


30, 60, 90, 120, 180


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