Benign prostatic hyperplasia (BPH) causes lower urinary tract symptoms (LUTS) due to bladder outlet obstruction (BOO) and overactive bladder (OAB). Treatment with dutasteride, a 5α-reductase inhibitor, improves LUTS but the mechanisms behind its mode of action remain to be elucidated. Researchers at Department of Renal and Urologic Surgery of the Asahikawa Medical University, found a correlation between clinical improvement and bladder vascular resistance before and after dutasteride treatment in BPH patients with LUTS. These results seem to explain the beneficial role of dutasteride in bladder symptoms and were published in a study entitled “Improvement of Overactive Bladder Symptoms and Bladder Ischemia with Dutasteride in Patients with Benign Prostatic Enlargement” in the journal LUTS.

The team performed a prospective study in 30 BPH patients who did not respond to alpha-adrenergic antagonist monotherapy used to treat mild to moderate BPH. They assessed patients before and 24 weeks after dutasteride treatment using the International Prostate Symptom Score (IPSS), prostate volume (PV) and by urodynamic parameters that measure urine storage and release. In addition, to measure bladder vascular resistive index (RI), patients underwent Doppler ultrasonography.

The team found a significant decrease in PV and improvement of IPSS after dutasteride administration. Bladder obstruction and RI were also significantly reduced as a result of increased bladder blood flow and reduced ischemia. After dutsteride treatment, patients without urgency, i.e persistent and urgent need to urinate, showed better parameters than patients with urgency. “Interestingly, the patients with no post-treatment urgency had lower BOOI and PdetQmax and better improvement of RI after dutasteride than those with persistent urgency. It seems that reduction of obstruction and improvement of bladder ischemia by dutasteride is a critical factor for resolution of OAB symptoms in patients with LUTS associated with BPE,” the authors wrote in their study.

Researchers also found increased testerone levels after dutasteride treatment, which may contribute to improve bladder ischemia. However, the number of patients studied was very small and results require further confirmation by larger sample studies.”Despite the small number of study patients, we believe that improvement of bladder blood flow by dutasteride is an important factor for resolution of OAB symptoms,” the authors concluded.