Topical phenylephrine increases anal canal resting pressure in patients with faecal incontinence

Introduction-The internal anal sphincter receives a stimulatory alpha, adre nergic innervation. Use of an adrenergic agonist may therefore have a role in treating patients with faecal incontinence. Methods-Ten patients (seven females, median age 66 years) with passive faec al incontinence related to weak internal anal sphincter were studied. All p atients had intact anal sphincters as assessed by endoanal ultrasound. Phen ylephrine gel was applied in a double blind manner in concentrations of 0%, 10%, 20%, 30%, and 40% (Slaco Pharma (UK) Ltd, Watford, UK) on separate da ys. Maximum resting anal pressure (MRP), anodermal blood flow, blood pressu re, and pulse rate were measured before, and one and two hours after applic ation. Results-All concentrations of phenylephrine gel increased median MRP (43, 4 8, 54, 65, and 70 cm H2O, for placebo, 10% (p=0.122), 20% (p=0.170), 30% (p =0.002), and 40% (p=0.004), respectively at one hour; comparisons with plac ebo). This was sustained at two hours. There was a clear dose-response rela tionship at one hour. Higher concentrations raised median MRP to within the normal range (> 60 cm H2O). At two hours, all concentrations greater than 20% increased the pressure to a similar degree, suggesting that the exact c oncentration may be important for the initial effect but given a certain th reshold is less important after a period of time. Toxicity was rare. Two pa tients experienced transient perianal burning which settled within a few mi nutes. There was no significant effect on anodermal blood flow, blood press ure, or pulse rate. Conclusion-This study has demonstrated the feasibility of using topical phe nylephrine to raise resting anal tone in patients with faecal incontinence. Randomised controlled trials are required to assess the efficacy of this a gent.