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.