[Effects of oxybutynin hydrochloride on the urinary bladder and urethra in in situ preparations]

Effects of oxybutynin on the urinary bladder and urethra were studied in comparison with atropine and flavoxate in cats and rabbits. Oxybutynin at 10 mg/kg, i.v., significantly inhibited the bladder contractions induced by electrical stimulation of the peripheral end in pelvic nerve. Oxybutynin was about one half the potency of atropine. On the contrary, 10 mg/kg of flavoxate, i.v., showed both effects of potentiation and inhibition. The bladder contractions induced by acetylcholine (ACh) and AHR-602 were markedly inhibited by oxybutynin and atropine. Oxybutynin was about one-fifteenth the potency of atropine. DMPP-induced contractions were inhibited by oxybutynin and atropine in a high dose, but oxybutynin was about two-fifths the potency of atropine. In addition, 3 mg/kg of oxybutynin, i.v., inhibited the contraction induced by hypogastric nerve stimulation, but 10 mg/kg of oxybutynin, i.v., significantly inhibited this contraction following initial potentiation. Oxybutynin showed an inhibitory effect on spontaneous rhythmical contraction, bladder tone and pelvic nerve discharge, similar to the effects of atropine. On the contrary, flavoxate potentiated this contraction and increased the bladder tone and pelvic and hypogastric nerve discharge. Urethra contractions induced by norepinephrine, ACh and hypogastric nerve stimulation were inhibited by oxybutynin, but not markedly. Oxybutynin and atropine dose-dependently increased the infusion volume, bladder volume capacity and micturition threshold pressure in the cystometrogram in rabbits. Flavoxate also increased them. From these results, it si suggested that oxybutynin is therapeutically a useful agent for pollakisurea nervosa.