Selective effect of nortriptyline on smooth muscle as an anticholinergic drug: a pharmacological and clinical study

The anticholinergic potency of nortriptyline was studied on muscle strips from human bladder and ileum. Concurrently the effect of nortriptyline low dosage therapy was studied in 21 women suffering from motor or sensory urgency and urge incontinence. Analysis of the results by the dose ratio method showed a significant difference in the affinity of the anticholinergic receptors to the antagonist. The Ki values were 0.298 microM for the bladder and 0.938 microM for the ileum. In the clinical study, the condition of 15 (71.4%) women treated with notriptyline improved considerably. The higher affinity of the drug to the receptors in the bladder than to those in the ileum may explain the positive therapeutic effect of a relatively low dose of nortriptyline in over 70% of the patients treated.