Lack of effficacy of botulinum toxin in chronic anal fissure

Abstract

Background and aim: Hypertonicity of internal anal sphincter plays a major role in the persistence of chronic anal fissure. Botulinum toxin could induce internal anal sphincter relaxation without the adverse effects of surgery (long-term faecal incontinence) or topical nitrates (anal burning, headaches, hypotension). Methods: We conducted a placebo-controlled, randomised, double-blind study to assess the efficacy of a single injection of botulinum toxin in the internal anal sphincter of patients with chronic anal fissure in six ambulatory care clinics. Eligibility criteria included a mean value of post-defecation anal pain ≥ 30 mm on a 100 mm visual analogue scale over the week preceding inclusion. Main endpoint was the proportion of patients with symptomatic improvement during the fourth week after inclusion (post-defecation anal pain below 10 mm). Results: Forty-four patients (22 in each group) were included. At inclusion, there was no significant difference between groups on age, sex ratio, pain duration, post-defecation anal pain, analgesic consumption and stool frequency. Ten (45%) and 11 (50%) patients reported symptomatic improvement on the main endpoint (P=0.76) in placebo and botulinum toxin groups, respectively. Ten patients (five in each group) had healed fissure at week 4 and ten patients (five in each group) required surgical treatment between weeks 4 and 12. Similarly, there was no significant difference between groups on other variables between weeks 4 and 12. Conclusions: The efficacy of a single injection of botulinum toxin in the internal anal sphincter does not differ from that of a placebo in patients with chronic anal fissure.