[Phase I study of flutamide, a nonsteroidal antiandrogen, in patients with prostatic cancer]

A phase I study of orally administered flutamide (a pure anti-androgen) was performed in 26 patients with prostatic cancer. No side effects were observed in 11 patients receiving single doses of either 125, 250, 375 or 500 mg. However, in the daily dosing schedule of 375, 750, 1125 and 1,500 mg/day doses, where medication was taken in three divided doses, discomfort in the stomach, nausea, vomiting and anorexia were experienced in one of the four patients receiving the highest dose of 1,500 mg. Nine patients receiving the other doses did not complain of toxic symptoms. Laboratory values did not change in the three patients receiving the lowest 375 mg/day dose, but elevation of transaminase was observed in five of the nine patients given higher doses. This elevation was observed in all the three patients receiving 1,500 mg/day dose. Among the serum hormone levels, significant increases of luteinizing hormone were observed. As for efficacy, objective responses were observed in two of the three patients in each of the four daily dosing groups. Improvement of pain, voiding obstruction symptoms, and performance status were also observed. Flutamide was found to be absorbed rapidly and to exist as a hydroxylated form (hydroxy-flutamide) in the plasma. The half-life of hydroxy-flutamide was similar in the single and daily administration, but the peak concentration and area under the concentration versus time curve in the daily administration became greater than those in the single administration. In conclusion, flutamide should be examined for efficacy and safety using doses of 375 to 1,125 mg/day in the phase II study.