What is the role of antispasmodic drugs in urinary incontinence treatment?

Updated: Mar 19, 2019
  • Author: Sandip P Vasavada, MD; Chief Editor: Edward David Kim, MD, FACS  more...
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Answer

Musculotropic relaxants depress smooth muscle activity directly but at a site distal to the cholinergic receptor. Relaxants also may work in part due to anticholinergic and local anesthetic properties at the level of the bladder. Oxybutynin is the prototype drug in this class. The typical dosage is 5 mg 2-4 times per day. Adverse effects are related mostly to the anticholinergic effects. Lower dosages, such as 2.5 mg 2-3 times a day, may be more appropriate for elderly patients.

Good-to-excellent results have been obtained in clinical trials, with improvement rates ranging from 61-86%. Oxybutynin is available in syrup and extended-release formulations. The extended release form is dosed 5-15 mg once daily and is of comparable efficacy to the parent drug.

One study that used specially prepared oxybutynin suppositories in patients who were intolerant of anticholinergic adverse effects when taking the oral form found that adverse effects via this route of administration were less, but the overall symptomatic improvement rate was only 48%. [1] Most of these patients were elderly.

Flavoxate is a direct smooth muscle relaxant with very weak anticholinergic properties. Few adverse effects are associated with its administration, but efficacy has been questionable. An observational study of flavoxate use in clinical practice described good results in decreasing daytime and nighttime urgency and the number of voids, but urge incontinence was not examined. [70] The usual dosage is 100-200 mg 3-4 times per day. This agent is not in common use in current practice.

Dicyclomine is a smooth muscle relaxant that has been used most commonly to treat irritable bowel syndrome. Moderate efficacy has been reported with a dosage of 10-20 mg taken orally 3 times daily. Adverse effects mostly are anticholinergic.


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