The efficacy and adverse effects of topical phenylephrine for anal incontinence after low anterior resection in patients with rectal cancer

Abstract

Anal incontinence is experienced by some patients with rectal cancer who received low anterior resection. This study was to examine the efficacy and adverse effects of the alpha-1 adrenergic agonist phenylephrine, which causes contraction of the internal anal sphincter and raises the resting pressure in these patients. Thirty-five patients with anal incontinence were treated with 30% phenylephrine or a placebo randomly allocated in a double-blind study. The efficacy of the drug was assessed by changes in the following standardized questionnaire scores: the fecal incontinence severity index (FISI), fecal incontinence quality of life (FIQL) scales, and a global efficacy question. Anal sphincter function was evaluated using anorectal manometry. Phenylephrine did not improve either the FISI score or any of the four FIQL scores. Five of 17 (29%) patients reported subjective improvement after phenylephrine compared with 4 of 12 (33%) using the placebo. The maximum resting anal pressure did not differ between baseline and after 4 weeks application of phenylephrine (30.0 to 27.3 mmHg). In the phenylephrine group, allergic dermatitis was developed in five patients and headache in two. In the patients with anal incontinence after low anterior resection for rectal cancer, phenylephrine gel did not seem to be helpful in relieving symptoms with some adverse effects.