This study compared the effects of phenylpropanolamine (PPA) and pseudoephedrine (PD) on the urethral pressure profiles of 9 spayed female dogs with histories of incontinence. Observed adverse effects and owner-reported continence scores were also evaluated. The dogs received either 1.5 mg/kg PD or PPA PO Q 8 H for 28 days. After a wash-out period of 14 days, the dogs were given the other drug at the same dose for the same period. Urethral pressure profiles of the dogs were done before treatment and on the last day of treatment. The study found significantly higher changes in maximum urethral closure pressure and functional area with PPA than with PD therapy. No change in functional profile length was found after either treatment. Owner-reported continence scores increased significantly after PPA, but not PD. More adverse effects, including panting, decreased appetite, and lethargy, were noted when dogs were receiving PD. As a result, the authors conclude that PD is inferior to PPA for treating canine urinary incontinence.

COMMENTARY: In this study, PPA seemed to be more effective and caused fewer side effects than PD when used to control incontinence in spayed female dogs, based on owner evaluation. In support of these owner impressions, urodynamic evaluation indicated that PPA was superior to PD in increasing maximum urethral closure pressure and the functional area of the urethra. The study suggests that PPA is a better choice of drug for treating incontinence in spayed dogs.

Effect of phenylpropanolamine and pseudoephedrine on the urethral pressure profile and continence scores of incontinent female dogs. Byron JK, March PA, Chew DJ, DiBartola SP. J Vet Intern Med 21:47-53, 2007.