Tolterodine is used treat overactive bladder (a condition in which the bladder muscles contract uncontrollably and cause frequent urination, urgent need to urinate, and inability to control urination). Tolterodine is in a class of medications called antimuscarinics. It works by relaxing the bladder muscles preventing bladder contraction.
Tolterodine comes as a tablet and an extended-release (long-acting) capsule to take by mouth. The tablet is usually taken twice a day. The extended-release capsule is usually taken once a day with liquids. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take tolterodine exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.
Summary from and more information available at MedlinePlus.gov.