AIM: To investigate the efficacy of topical application of 0.5% nifedipine ointment in healing acute anal fissue and preventing its progress to chronicity.METHODS: Thirty-one patients (10 males, 21 females)with acute anal fissure from September 1999 to January 2005 were treated topically with 0.5% nifedipine ointment (t.i.d.) for 8 wk. The patients were encouraged to follow a high-fiber diet and assessed at 2, 4 and 8wk post-treatment. The healing of fissure and any side effects were recorded. The patients were subsequently followed up in the outpatient clinic for one year and contacted by phone every three months thereafter,while they were encouraged to come back if symptoms recurred.RESULTS: Twenty-seven of the 31 patients completed the 8-wk treatment course, of them 23 (85.2%)achieved a complete remission indicated by resolution of symptoms and healing of fissure. Of the remaining four unhealed patients (14.8%), 2 opted to undergo lateral sphincterotomy and the other 2 to continue therapy for four additional weeks, resulting in healing of fissure. All the 25 patients with complete remission had a mean follow-up of 22.9 ± 14 (range 6-52) mo. Recurrence of symptoms occurred in four of these 25 patients (16%)who were successfully treated with an additional 4-wk course of 0.5% nifedipine ointment. Two of the 27 (7.4%)patients who completed the 8-wk treatment presented with moderate headache as a side effect of nifedipine.CONCLUSION: Topical 0.5% nifedipine ointment, used as an agent in chemical sphincterotomy, appears to offer a significant healing rate for acute anal fissure and might prevent its evolution to chronicity.