Three trials were included in the review (n=180 patients); sample size ranged from 30 to 100. The methodological quality of the included trials was considered to be inadequate, with unclear reporting of allocation concealment and blinding. The mean follow-up ranged from two months to 36 months.
Botulinum toxin and glyceryltrinitrate were found to be equally effective in healing and improving chronic anal fissure, with no statistically significant differences observed in effectiveness, although there was significant heterogeneity across the results of the three trials (Q=4.03; p<0.042).
Treatment with glyceryltrinitrate was associated with a higher incidence of total side effects (RR 0.14, 95% CI 0.05 to 0.40) and headache (RR 0.06, 95% CI 0.01 to 0.30). There was no statistically significant heterogeneity observed for these outcomes.
One trial (n=30 patients) reported a recurrence rate of chronic anal fissure of 33% in the botulinum toxin group and 40% in the glyceryltrinitrate group at a mean follow-up time of three years.