How does tolterodine help decrease urinary tract spasms?

Ms. James is in the clinic for her annual checkup andexpresses a concern about how frequently she has to urinate.
Careful questioning determines that she has to get up two to
three times at night to urinate and has started wearing pads
to protect against sudden leaking. Urine tests are negative for
bacteria. The physician has diagnosed urinary spasms and
has ordered tolterodine (Detrol LA). Ms. James asks if that is
the drug that is advertised on the TV.
a. How does tolterodine help decrease urinary tract
spasms?
b. What are common adverse effects that Ms. James
should be told she might experience?