Clinical efficacy of a loading dose of naftopidil for patients with benign prostate hyperplasia

The efficacy of a loading dose of α(1)-adrenoreceptor antagonist for patients with benign prostate hyperplasia who did not improve at a low dose has not been determined. We performed a prospective study to estimate the efficacy of incremental naftopidil administration.

The efficacy of naftopidil was examined based on changes in the International Prostate Symptom Score (IPSS). We defined a "responder" as a patient who improved by ≥5 points in IPSS total score. All patients were administered naftopidil at 50 mg/day for 12 weeks, and nonresponders at 50 mg/day were increased to 75 mg/day. Efficacy was finally evaluated after an additional 12 weeks of administration at 75 mg/day.

Among 122 patients whose data could be analyzed, the efficacy rate after administration at 50 mg/day was 52.5%. In all IPSS items except urgency score, the responders had significantly higher (poorer) values than nonresponders before the start of treatment. Of 40 patients whose dose was increased to 75 mg/day and whose data could be analyzed, prostate volume in the responder group (9 patients) was significantly smaller than that in the nonresponder group (31 patients). Multivariate analysis showed that patients with improved IPSS total score, voiding symptoms, urgency, and weak stream after administration of 50 mg/day naftopidil were more likely to improve after a dose increase.

A dose increment of naftopidil to 75 mg/day may be useful in patients with BPH who did not improve at 50 mg/day.