BACKGROUND:Previous laboratory studies have shown that angiotensin II is produced locally in the rat internal anal sphincter causing potent contraction. The aim of this first human study was to evaluate the safety and manometric effects of topical application of captopril (an ACE inhibitor) on the resting anal pressure in healthy adult volunteers. METHODS:Ten volunteers, mean age 32.5 years (range, 19-48 years), underwent anorectal manometric evaluation of the mean anal resting pressure (MRAP) and the length of the high-pressure zone (HPZ) before 20 and 60 min after topical application of captopril (0.28 %) cream. Cardiovascular variables (systolic blood pressure, diastolic blood pressure and pulse) were measured before and for up to 1 h after cream application. Side effects were recorded. Adverse events and patient comfort after the cream application were evaluated within a 24-h period by completing a questionnaire. RESULTS:There was no significant change overall in MRAP following captopril administration, although in half the patients, there were reductions in MRAP after treatment. Half the patients had a reduction in the mean resting HPZ length; however, there was no overall difference between pre- and post-treatment values. There was no effect on basic cardiovascular parameters and no correlation between manometric and cardiovascular variables. CONCLUSIONS:Topical application of captopril cream may result in a reduction in MRAP in volunteers without anorectal disease. Its use is associated with minimal side effects. It may be a new potential therapeutic option in the treatment of anal fissure. Further studies are required to determine the optimal concentration, dose and frequency of application.