 The purpose of this study is to compare the efficacy of DITROPANÂ XL oxybutynin chloride Extended-Release Tablets and DETROLÂ LA tolterodine tartrate extended-release capsules in the reduction of urge urinary incontinence episodes during a 12-week treatment period in patients with overactive bladder. The secondary objective is to compare the tolerability of DITROPANÂ XL oxybutynin chloride and DETROLÂ LA tolterodine tartrate during a 12-week treatment period. 