Oxybutynin possesses
anticholinergic and
spasmolytic properties, which together form the basis for its use as a therapeutic option in patients with
overactive detrusor function--either idiopathic detrusor instability (DI) or detrusor
hyperreflexia. Of the symptoms of detrusor overactivity,
urge incontinence is often the most distressing to the patient.
Urge incontinence and other subjective parameters (urinary frequency, urgency) improve in tandem with objective (cystometric) measures (maximum detrusor pressure during filling, volume at first desire to void, maximum bladder capacity) in ambulatory, including elderly, patients treated with
oxybutynin. However, on the basis of results of limited investigations, the
drug appears ineffective in elderly institutionalised individuals. Relative to other
anticholinergic drugs,
oxybutynin appears at least as effective as
propantheline and similar in efficacy to
propiverine in small trials, although these results are not definitive. Further investigation of intravesical
oxybutynin may lead to this route becoming an option in patients with pre-existing
catheters. Adverse effects--dry mouth,
constipation, blurred vision--related to the
anticholinergic activity of
oxybutynin occur frequently and can be sufficiently troublesome to necessitate treatment discontinuation in up to 25% of patients, depending on the dosage. Increases in residual urine volume suggesting
urinary retention (undesirable in patients with idiopathic DI), also can develop in some
oxybutynin recipients. In summary,
oxybutynin is one of the few drugs proven to be beneficial in some patients with
overactive detrusor function. Despite the occurrence of unwanted
anticholinergic effects in many patients, and apparent lack of efficacy in the elderly institutionalised population,
oxybutynin should be considered for the
drug of first choice in patients with detrusor overactivity, including the elderly ambulatory population, when pharmacological
therapy is indicated.