Topical phenylephrine increases anal canal resting pressure in patients with faecal incontinence.
BACKGROUND
The internal anal sphincter receives a stimulatory alpha(1) adrenergic 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 faecal incontinence related to weak internal anal sphincter were studied. All patients had intact anal sphincters as assessed by endoanal ultrasound. Phenylephrine 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 days. Maximum resting anal pressure (MRP), anodermal blood flow, blood pressure, and pulse rate were measured before, and one and two hours after application.


RESULTS
All concentrations of phenylephrine gel increased median MRP (43, 48, 54, 65, and 70 cm H(2)O, 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 placebo). This was sustained at two hours. There was a clear dose-response relationship at one hour. Higher concentrations raised median MRP to within the normal range (> 60 cm H(2)O). At two hours, all concentrations greater than 20% increased the pressure to a similar degree, suggesting that the exact concentration may be important for the initial effect but given a certain threshold is less important after a period of time. Toxicity was rare. Two patients experienced transient perianal burning which settled within a few minutes. There was no significant effect on anodermal blood flow, blood pressure, or pulse rate.


CONCLUSIONS
This study has demonstrated the feasibility of using topical phenylephrine to raise resting anal tone in patients with faecal incontinence. Randomised controlled trials are required to assess the efficacy of this agent.
Cheetham
M J
MJ
St Mark's Hospital, Watford Road, Harrow, Middlesex HA1 3UJ, UK.
Kamm
M A
MA
Phillips
R K
RK
D000287:Administration, Topical; D000316:Adrenergic alpha-Agonists / Q000008:administration & dosage*; D000368:Aged; D001003:Anal Canal / Q000098:blood supply; D001004:Anus Diseases / Q000188:drug therapy*; D001794:Blood Pressure / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D005242:Fecal Incontinence / Q000188:drug therapy*; D005260:Female; D005782:Gels; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008297:Male; D008365:Manometry; D010656:Phenylephrine / Q000008:administration & dosage*; D012039:Regional Blood Flow
D000316:Adrenergic alpha-Agonists; D005782:Gels; D010656:Phenylephrine