A study of the anticholinergic and antispasmodic activity of oxybutynin (Ditropan) on rabbit detrusor.

Experiments have been conducted which show that while the tertiary amine oxybutynin has only moderate in vitro anticholinergic and antihistaminic activity, it is a potent inhibitor of barium chloride-induced spasms of rabbit detrusor muscle. Oxybutynin exerts 1/13 the anticholinergic activity of propantheline and 1/4 that of atropine, but produces approximately 2x the inhibition of barium chloride-induced spasm than propantheline and 10x the inhibition produced by atropine. In sum, oxybutynin possesses a notable antispasmodic activity distinct from its anticholinergic activity and stronger than that of atropine, propantheline, or methantheline, which may prove useful in the treatment of smooth muscle hypermotility.