Botulinum toxin A for the treatment of chronic anal fissure.

Since its introduction for the treatment of strabismus, botulinum toxin (BoNT) has been increasingly used in the treatment of several disorders with excessive or inappropriate muscle contractions. The therapeutic effects of BoNT occur through the temporary chemodenervation caused by the injection into the local target muscle or skin. Modulation of muscle relaxation may be achieved by varying the dose of BoNT solution injected; most adverse effects are transient. Indeed, botulinum neurotoxin has been used to selectively weaken the internal anal sphincter as a treatment for chronic anal fissure in several randomized, controlled trials and open-label studies. The use of botulinum neurotoxin seems to be an effective and safe approach for the treatment of chronic anal fissure, particularly in patients at high risk for incontinence.