The optically pure R(-)-isomer of oxybutynin and the optically pure R(-)-isomer of desethyl-oxybutynin, which are substantially free of the corresponding S(+)-isomers, are potent anticholinergic spasmolytics, useful for relief of symptoms associated with urinary bladder smooth muscle hyperactivity, such as Urinary Incontinence and gastrointestinal smooth muscle hyperactivity, such as Irritable Bowel Syndrome. Methods are disclosed utilizing the optically pure R(-)-isomers of oxybutynin and desethyloxybutynin for treating cholinergically mediated smooth muscle hyperactivity while minimizing the side effects associated with administration of racemic oxybutynin or racemic desethyloxybutynin.