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

Background: 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. Patients and methods: 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. Results: 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. Conclusion: 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.