Tolterodine (Detrol) is used to treat overactive bladder (OAB) in adults. It's an anticholinergic medication that helps with bladder control to lessen the need to go to the restroom suddenly or often. The immediate-release tablet (Detrol) is taken by mouth twice a day. There's also an extended-release capsule (Detrol LA) that's taken just once a day. Both formulations come in brand-name and generic-name versions. Tolterodine (Detrol) can commonly cause dry mouth. Other side effects can include headache and constipation.