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Pharmacokinetics, Metabolism, and Saliva Output During Transdermal and Extended-Release Oral Oxybutynin Administration in Healthy Subjects

2003; Elsevier BV; Volume: 78; Issue: 6 Linguagem: Inglês

10.4065/78.6.696

1942-5546

Rodney A. Appell, Michael B. Chancellor, R. Howard Zobrist, Heather Thomas, Steven W. Sanders,

Stress Responses and Cortisol

To compare the pharmacokinetics and adverse effect dynamics of 2 modified-release oxybutynin treatments.Between October 15 and November 6, 2001, 13 healthy subjects (7 men and 6 women) participated in a randomized, 2-way crossover study of transdermal (Oxytrol, 3.9 mg/d) and extended-release oral (Ditropan XL, 10 mg) oxybutynin. Multiple blood and saliva samples were collected. Pharmacokinetic parameters and total salivary output were assessed. Statistical analyses included 95% confidence intervals, paired t test, analysis of variance, and linear regression.Steady-state plasma concentrations were achieved after the first transdermal application and after the second extended-release oral dose. Mean +/- SD 24-hour oxybutynin areas under the concentration-time curve were comparable during transdermal and oral extended-release treatments, 10.8 +/- 24 vs 9.2 +/- 33 ng x h(-1) x mL(-1), respectively. However, the ratio of area under the curve (N-desethyloxybutynin/oxybutynin) after transdermal administration (1.2 +/- 03) was significantly lower (P < .001) than after extended-release oral administration (4.1 +/- 0.9). Mean plasma concentrations were less variable during transdermal compared with extended-release oral administration. Mean +/- SD saliva output was greater during transdermal than extended-release oral treatment (15.7 +/- 93 vs 12.2 +/- 6.8 g, respectively; P = .02). Lower N-desethyloxybutynin during transdermal application was associated with greater saliva output (r = -059, P = .04). No clinically important treatment-related adverse effects were observed.Transdermal oxybutynin administration results in greater systemic availability and minimizes metabolism to N-desethyloxybutynin compared with extended-release oral administration. Lower N-desethyloxybutynin plasma concentration and greater saliva output during transdermal treatment correspond to the reported low incidence of dry mouth in patients with overactive bladder.