Results of Double-blind Placebo-controlled Crossover Study of Sildenafil Citrate (Viagra) in Women Suffering from Obstructed Voiding or Retention Associated with the Primary Disorder of Sphincter Relaxation (Fowler's Syndrome)

Objectives: Women with the primary disorder of sphincter relaxation find voiding difficult. Studies have identified neuronal nitric oxide synthase in the female urethral sphincter, and nitric oxide donors have been shown to decrease sphincter pressures. The aim of our study was to determine if sildenafil could improve sphincter relaxation and thereby increase flow rates and improve bladder emptying.

Methods: Twenty women with complete (5), partial retention or obstructed voiding (15) with a maximum flow rate (Qmax) of less than 15 ml/min with an elevated maximal urethral closure pressure (92--age cm H(2)O) and sphincter volume (>1.6 cm(3)) were included in the study. The study was a double-blind, randomised, placebo-control, crossover design, with patients taking sildenafil or placebo, and with measurement of flow rate and residual volume at baseline and after each treatment phase. Voiding diary, quality of life, and International Prostate Symptom Score (IPSS) data were also collected.

Results: No statistical significant difference was seen in any voiding parameters and diaries when sildenafil citrate was compared with placebo. There was a significant mean decrease in IPSS of 3.64 between baseline and the sildenafil phase (p=0.0083), but not when compared with placebo. In the subgroup of women with partial retention and obstructed voiding (15/20), there was a statistically significant increase in Qmax of 4.7 ml/sec (p=0.025) between sildenafil and baseline; however this difference was not seen when compared with placebo.

Conclusions: This is the first study looking at sildenafil in voiding dysfunction in women. Clinical improvements with sildenafil were not significant when compared with placebo. Sildenafil was not effective as a therapeutic pharmacologic agent in this group of patients.