Pharmacokinetics and clinical effects of oxybutynin in geriatric patients.

The pharmacokinetics and clinical effects of oxybutynin were examined among 21 elderly (mean age 84 years) patients with urge incontinence and detrusor instability or hyperreflexia. The drug did not accumulate to high levels after a week of treatment at dosages of either 2.5 or 5 mg. 3 times per day, and the mean peak level on 5 mg. among the elderly (12.5 ng. per ml.) was not statistically different than the mean peak level reported after the same dosage in young healthy men (8.9 ng. per ml., p equals 0.4). There were no clinically meaningful changes in heart rate, blood pressure or intraocular pressure during the treatment periods. Two-thirds of the patients suffered at least 1 side effect, most commonly dryness of the mouth that was not severe enough to warrant discontinuation of the drug. These data suggest that oxybutynin chloride at dosages of 2.5 to 5 mg. 3 times per day is safe for use in the elderly, even among octogenarians. Statements about its effectiveness and efficacy in the geriatric population must await controlled clinical trials.