Efficacy of mirabegron for overactive bladder with human T cell lymphotropic virus‐1 associated myelopathy

OBJECTIVE: Mirabegron is widely considered as an effective and safe drug for patients with overactive bladder (OAB). However, there is no evidence regarding the efficacy of mirabegron in human T cell lymphotropic virus‐1 (HTLV‐1)‐associated myelopathy/tropical spastic paraparesis (HAM/TSP) patients with OAB symptoms. The aim of the present study was to clarify the efficacy of mirabegron in HAM/TSP patients with OAB symptoms. METHODS: The present study evaluated the efficacy of mirabegron treatment (50 mg, once daily) in nineteen HAM/TSP patients with OAB symptoms by assessing subjective symptoms using the overactive bladder symptom score (OABSS) and International Prostate Symptom Score (IPSS) before and 12 weeks after administration. Voided volume (VV), maximum flow rate (Q(max)), and post‐void residual (PVR) urine volume were evaluated as objective symptoms. RESULTS: Mirabegron treatment improved OABSS in terms of night‐time frequency, urgency, and total score (P < .001). In addition, on the IPSS, mirabegron therapy improved urgency, nocturia, storage symptoms (Questions 2, 4 and 7 on the IPSS), as well as the total score (P < .001). The quality of life (QoL) on the IPSS also improved after treatment (P < .001). However, there were no significant changes in objective symptoms, as measured by VV, Q(max), and PVR, after treatment. One patient (5.3%) complained of dry mouth; because this adverse effect was very mild, the patient did not discontinue mirabegron. CONCLUSIONS: Mirabegron administration improved subjective symptoms in HAM/TSP patients with neurogenic OAB.