A controlled trial of the effect of 4-hydroxypyrazolopyrimidine (allopurinol) on the toxicity of a single bolus dose of 5-fluorouracil.

We have evaluated, in a controlled study, the modification of the toxicity of a single bolus dose of 5-fluorouracil (5-FU) by allopurinol. Patients first received a single dose of 5-FU and were monitored for toxicity. If a measurable nadir in WBC or platelet count occurred, then the same dose of 5-FU was repeated with concurrent allopurinol, given for four consecutive days at an initial dose of 300 mg twice daily, starting the day before the administration of 5-FU. With this schedule, each evaluable patient received courses of 5-FU with and without allopurinol that could be compared for toxicity. Twenty patients received initial 5-FU doses of either 1,200 mg/m2 or 1,500 mg/m2 and later had the same dose repeated with allopurinol. Nineteen of these patients had a higher WBC count with allopurinol than without it. In several patients who received a further course of 5-FU with 900-mg/d allopurinol, the WBC count was yet higher than with 600-mg/d allopurinol. The myelosuppression produced by 5-FU was characte...