This is the Scientific Surgery Archive, which contains all randomized clinical trials in surgery that have been identified by searching the top 50 English language medical journal issues since January 1998. Compiled by Jonothan J. Earnshaw, former Editor-in-Chief, BJS
L‐Erythro‐methoxamine is more potent than phenylephrine in effecting contraction of internal anal sphincter in vitro. BJS 2003; 90: 872-876.
Published: 14th April 2003
Authors: O. M. Jones, J. M. Thompson, A. F. Brading, N. J. McC. Mortensen
Background
Topical phenylephrine has been shown to increase resting anal canal pressure in normal and incontinent individuals. However, high concentrations of gel (10–40 per cent) are required that may cause local side‐effects. The aim of this study was to determine whether methoxamine, another α‐1‐adrenoceptor agonist, might be a more potent alternative to phenylephrine.
Method
Porcine internal anal sphincter (IAS) tissue was cut into strips, suspended in a superfusion organ bath and allowed to equilibrate. Strips were subjected to each drug under test for 20 s, sufficient to obtain stable tone. Phenylephrine, methoxamine (1 : 1 : 1 : 1 ratio of its four isomers) and each of the individual isomers of methoxamine were evaluated in turn.
Results
In vitro, methoxamine racemate and phenylephrine were similarly potent in causing contraction of IAS strips (mean(s.e.m.) dose giving half maximal effect (EC50) at 74·7(16·5) versus 58·3(13·4) µM respectively; P = 0·443). However, one of the methoxamine isomers,