Optimal Dosing of Botulinum Toxin for Treatment of Chronic Anal Fissure: A Systematic Review and Meta-Analysis.

[BACKGROUND] Chronic anal fissures are associated with significant morbidity and reduced quality of life. Studies have investigated the efficacy of botulinum toxin with variable results; thus, there is currently no consensus on botulinum toxin dose or injection sites.

[OBJECTIVE] This study aimed to systematically analyze trials studying the efficacy of botulinum toxin for treatment of chronic anal fissure to identify an optimum dosage and injection regimen.

[DATA SOURCES] A comprehensive review of the literature was conducted according to PRISMA guidelines. PubMed/Medline, Embase, Scopus, and the Cochrane Library were searched from inception to June 2015.

[STUDY SELECTION] All clinical trials that investigated the efficacy of botulinum toxin for chronic anal fissure were selected according to specific criteria.

[INTERVENSIONS] The interventions used were various doses of botulinum toxin.

[OUTCOME MEASURES] Clinical outcomes, dosage, and injection site data were evaluated with weighted pooled results for each dosage and 95% confidence intervals.

[RESULTS] There were 1158 patients, with 661 in botulinum toxin treatment arms, from 18 clinical trials included in this review. The outcomes of interest were 3-month healing, incontinence, and recurrence rates. Meta-regression analysis demonstrated a small decrease in healing rate (0.34%; 95% CI, 0-0.68; p = 0.048) with each increase in dosage, a small increase in incontinence rate (1.02 times; 95% CI, 1.0002-1.049; p = 0.048) with each increase in dosage and a small increase in recurrence rate (1.037 times; 95% CI, 1.018-1.057; p = 0.0002) with each increase in dosage. The optimum injection site could not be determined.

[LIMITATIONS] This study was limited by weaknesses in the underlying evidence, such as variable quality, short follow-up, and a limited range of doses represented.

[CONCLUSIONS] Fissure healing with lower doses of botulinum toxin is as effective as with high doses. Lower doses also reduce the risk of incontinence and recurrence in the long term.