Effects of phenoxybenzamine hydrochloride on canine lower urinary tract: clinical implications

The results of our study show that phenoxybenzamine hydrochloride, a potent long-acting alpha-adrenergic blocker, has clearly demonstrable effects on urethral function. In a dose of 0.5 mg. per kilogram of body weight it caused a significant lowering of the resting urethral pressure, a decrease in the arterial pressure, and no change in the intravesical pressure. Higher doses caused similar but more pronounced and prolonged effects. The combined use of phenoxybenzamine and bethanechol increased the intravesical pressure and decreased the urethral pressure. It appears that the predominant mechanism of urethral resistance is alpha-adrenergic activity in smooth muscle. A review of the medical literature, our experimental studies, and limited clinical application lead uo to conclude that phenoxybenzamine could be useful in treating neurogenic vesical dysfunction of various types, urethral syndrome, urgency incontinence, functional outlet obstruction with or without vesicoureteral reflux, drug-related obstructive urinary symptoms, partial prostatic obstruction, and ureteral colic. The combination of phenoxybenzamine and bethanechol could be used in managing patients with atony of the bladder of neuropathic or myopathic origin.