To test this hypothesis, an AR inhibitor developed by Pfizer Inc., sorbinil, was studied in this clinical trial. (Other AR inhibitors underwent study in clinical trials sponsored by Ayerst and Alcon.) Initially, 402 patients were randomized into the double-masked treatment period using a dosage schedule of one 250-mg tablet daily. In 1985, recruitment was voluntarily halted by Pfizer because of several serious hypersensitivity reactions among patients taking sorbinil in clinical trials in the United States and Europe. In November 1985, recruitment resumed, using a titrated dosage schedule of 25 mg daily for 2 weeks, followed by 75 mg daily for 2 weeks, then 250 mg daily for the duration. A total of 497 patients participated in the study.