Frentizole therapy of thrombocytopenia in systemic lupus erythematosus and refractory idiopathic thrombocytopenic purpura.

Frentizole, an immunosuppressive phenylurea agent, used in a dosage of 4 mg/kg per day, was found to produce quick elevation of platelet counts in three thrombocytopenic patients. Two have systemic lupus erythematosus, and one has resistant idiopathic thrombocytopenic purpura. Corticosteroid dosage could be reduced in all three patients, and thus far platelet counts are being maintained at "safe" levels. Although major toxicity has limited the utility of frentizole, its effect on the platelet counts of these thrombocytopenic patients is of interest.