Chronic anal fissure: botulinum toxin type A injection

How well does botulinum toxin type A injection work?

Two reviews looked at a number of different studies of botulinum toxin type A injection when used to treat chronic anal fissure in adults. No studies were found which included children or young people.

Botulinum toxin type A worked much better at healing chronic anal fissures in some studies than others. This variation in whether botulinum toxin healed the fissures can be partly explained by the fact that the studies included in the 2 reviews looked at whether the fissures had healed at different periods of time after the treatment had been given. This ranged from just 1 or 2 months after the treatment to 5 years. This is important because anal fissures can naturally go through temporary periods of being completely healed or only partly healed, only for the fissure to come back later. A lot of the studies looked at how well the fissures had healed less than 6 months after the treatment was given. This doesn't give a good idea of how well the treatment works over a longer period of time because it doesn't take into account how often the fissure might come back. The studies were not long enough to show this.

There was a large difference between the studies in how often the fissure returned (reoccurred) after it had initially been healed when botulinum toxin type A injection had been used. This is because studies measured this at different points in time.

Despite the large variation between studies, 1 of the reviews found that botulinum toxin type A injection healed chronic anal fissure in around 6 to 7 out of every 10 people who were given the injection. However, botulinum toxin type A injection was found to be no better or worse at healing anal fissures than a dummy treatment with no active ingredient (also called a placebo). This might be because many chronic anal fissures temporarily heal on their own anyway, without treatment.

Overall, the studies also showed that botulinum toxin type A injection was no better or worse at healing fissures than a 0.2% strength of glyceryl trinitrate ointment. Some studies found botulinum toxin type A injection worked better than the ointment, others found it didn't, and others found they were the same. Importantly, the 0.2% strength of glyceryl trinitrate ointment used in the studies is not licensed in the UK. No studies were found that compared botulinum toxin with the 0.4% strength of glyceryl trinitrate ointment, which is currently the only treatment that is licensed in the UK for treating chronic anal fissure.

The studies included in the reviews showed that botulinum toxin did not work as well as surgery (a procedure called 'sphincterotomy') at healing chronic anal fissures. Surgery works well at healing anal fissures but there is a small chance of complications from the surgery. Therefore surgery is usually tried only after other treatments that don't involve surgery, such as glyceryl trinitrate ointment, diltiazem cream or botulinum toxin type A injection, haven't worked.

What are the possible harms or side effects?

One review of studies found that a side effect of using botulinum type A injection was temporary loss of control of flatulence (or passing wind) in about 1 in 10 people who were given the injection. Up to 1 in 20 people who are given the injection may also lose control of their bladder or bowel movements, which usually does not last for long. Potentially serious side effects that can be caused by using botulinum toxin over a long period of time cannot be ruled out as most of the studies were short and didn't last very long.

If you are receiving any product containing botulinum toxin, you should be aware of the rare, but serious signs and symptoms that the toxin has spread. These include weakness in your muscles or difficulties with breathing. You should see a doctor immediately if you have any of the following symptoms because they may be life-threatening: