Purinase Overdosage

Ingestion of 20 g allopurinol resulted in nausea, vomiting, diarrhea, and dizziness in one patient who eventually recovered following general supportive measures. However, ingestion of larger doses of allopurinol (i.e., up to 22.5 g) without adverse effects has also been reported.
Massive absorption of allopurinol may result to considerable inhibition of xanthine oxidase activity, which should have no untoward effects unless 6-mercaptopurine and/or azathioprine are being concomitantly administered.
There is no specific antidote for allopurinol in the management of overdosage. The drug should be withdrawn, and patients should be monitored. Normal supportive measures should be provided. Adequate hydration should be guaranteed to maintain optimum diuresis to facilitate urinary excretion of allopurinol and its metabolites. If other forms of acute distress occurred, gastric lavage should be considered; otherwise, symptomatic treatment should be provided.
Hemodialysis may be used if necessary.