Question

A physician is evaluating a 62-year-old patient who reports highly distressing urinary symptoms that have persisted for the past eight months. She states that she frequently experiences an abrupt, overwhelming need to urinate, which is often followed by a large volume of urine loss before she can reach the bathroom. These episodes occur 4 to 5 times daily. There is no history of leakage associated with physical exertion, sneezing, or coughing. Her medical history includes well-controlled hypertension, narrow-angle glaucoma, and severe chronic idiopathic constipation that requires daily osmotic laxatives. Pelvic examination reveals normal vaginal rugae without erythema or atrophy, and there is no evidence of pelvic organ prolapse. The cough stress test is negative. Postvoid residual volume is 25 mL. Urinalysis shows no abnormalities. The patient has diligently completed an 8-week behavioral therapy program, including timed voiding and pelvic floor muscle training, with minimal improvement. Which of the following pharmacologic mechanisms is most appropriate to target for symptom relief in this patient?