A double-blind randomized trial of low-dose oral urea to prevent sickle cell crises.

Seventy-nine homozygous SS patients were randomly assigned to control or oral prophylactic urea treatment in a double-blind trial designed to determine whether prophylactic oral urea, in low doses, prevents sickle cell crises. The average follow-up time for these patients was 13.7 months and 33 patients were diagnosed as having one or more crises during the study. No statistically significant treatment differences were found in weight changes, bilirubin changes, or hemoglobin changes over the course of the study or in the distribution of time to first crises or time to second crisis. This study gives no evidence in favor of the hypothesis that prophylactic oral urea, in low doses, prolongs time to crisis.