α1D/A-adrenoceptor antagonist naftopidil for the male lower urinary tract symptoms associated with benign prostatic hyperplasia: efficacy of dose increase therapy.

Objectives: To examine the efficacy of dose increase therapy in patients with lower urinary tract symptoms associated with benign prostatic hyperplasia who responded poorly to 50 mg/day of naftopidil.

Methods: A total of 95 patients received 50 mg/day of naftopidil for 8 weeks. After this treatment period, they were divided into two groups: the poor responders were defined as those who either had an International Prostate Symptom Score-Quality of Life ≥ 4 or with an International Prostate Symptom Score-Quality of Life of 3 whose International Prostate Symptom Score-Quality of Life improved <2 points (group A). All other patients were defined as responders to naftopidil 50 mg/day (group B). The dose of naftopidil was increased to 75 mg/day in group A, and maintained at 50 mg/day in group B. The treatment was continued for a further 8 weeks.

Results: The prostate volume at the baseline was significantly larger in group A than group B. The improvement of International Prostate Symptom Score total score, International Prostate Symptom Score-Quality of Life, and voided volume after 8 weeks was significantly better in group B than in group A. However, there was no significant difference in the changes of all parameters between the two groups after 16 weeks.

Conclusions: A dose increase to 75 mg/day is an effective treatment strategy in patients with lower urinary tract symptoms associated with benign prostatic hyperplasia who responded poorly to an initial dose of 50 mg/day of naftopidil. Furthermore, a starting dose of 75 mg/day should be considered in patients with a large prostate volume, as this is a predictive factor for dose increase.