Botulinum might be more effective than nitroglycerine in anal fissure

Clinical Question

Is type A botulinum toxin more effective than nitroglycerine ointment in treating chronic anal fissure?

Bottom Line

In this study, botulinum toxin (Botox, Dysport) appeared slightly more effective than topical nitroglycerine in managing chronic anal fissures. (LOE = 2b)


Brisinda G, Cadeddu F, Brandara F, Marniga G, Maria G. Randomized clinical trial comparing botulinum toxin injections with 0.2 per cent nitroglycerin ointment for chronic anal fissure. Br J Surg 2007;94:162-167.  [PMID:17256809]

Study Design

Randomized controlled trial (single-blinded)


Unknown/not stated




Outpatient (specialty)


These authors randomly assigned 100 patients with anal fissure of at least 2 months duration to receive type A botulinum (30 units Botox or 90 units Dysport; administered as 2 injections of equal volume, one on each side of the anterior midline of the internal anal sphincter) or topical nitroglycerine (2 grams of 2% nitroglycerine diluted in 100 grams of soft paraffin) applied to the anus and anal canal 3 times daily for 8 weeks. The patients, who were aware of the treatment administered, were evaluated every month by physicians unaware of the treatment. Patients who had persisting fissures after 8 weeks were offered a sphincterotomy or the alternate treatment. The authors don't describe using an intention-to-treat analysis. No patients were lost to follow-up. At the end of 8 weeks, 92% of patients treated with botulinum toxin were healed compared with 70% of those treated with nitroglycerine (number needed to treat = 5; 95% CI, 3-16). Since the lack of an intention-to-treat analysis tends to magnify treatment effects, it is possible that the real benefit may be smaller. Patients treated with botulinum were more likely to experience 3 weeks of "mild incontinence to flatus," while those treated with nitroglycerine were more likely to experience transient headaches.