[Effect of KT-611 (Naftopidil) on the contraction of human prostatic tissue and its use in benign prostatic obstruction].

A new alpha 1-adrenergic receptor antagonist, KT-611 (naftopidil) antagonized dose dependently the contraction induced by agonists, noradrenaline and phenylephrine in the human prostatic tissue. KT-611 at a dosage of once or twice a day was evaluated for its effects on 49 patients with benign prostatic hypertrophy. The drug improved subjective and objective symptoms significantly. The residual urine was reduced in volume and percentage significantly. The average and maximum flow rates increased significantly. The optimal dosage was presumed to be in the range of 25 to 75 mg once a day or 25 to 100 mg twice a day. Adverse reactions and abnormal laboratory findings were all slight. KT-611 was concluded to be useful in the treatment of patients with benign prostatic hypertrophy.