Oxybutynin is used to treat overactive bladder (OAB). Oral oxybutynin is available as a short-acting tablet and solution that is taken 2 to 4 times a day. It also comes as a long-acting tablet that's taken once daily (brand name Ditropan XL). Some common side effects of oxybutynin include dry mouth, constipation, and dizziness. Older adults typically lower doses of this medication to lower the risk for side effects.