Combined use of type A and F botulinum toxins for blepharospasm: A double-blind controlled trial

Type A botulinum toxin has widened its clinical range of applications, but the risk of developing antibodies limits the repeated use of high-dose inje ction. To minimize the risk, mixing different types of toxin might reduce t he antigenic presentation of a specific toxin and associated proteins. At t he same time, inhibition of the neuromuscular release process at the multip le sites might potentiate the clinical response or the duration of action. We compared the effectiveness of a mixture of type A and type F botulinum t oxins with that of type A or type F toxin alone for treating patients with blepharospasm in a double-blind study. Fifty-four patients had 10 units of toxin injection, a mixture of type A and F toxins (including 5 units of eac h) on one side and either type A or F toxin on the other side of the orbicu laris oculi muscle. Clinical evaluation at 4 and 10 weeks after the injecti on revealed that the peak clinical effect at 4 weeks was similar among the three preparations. The duration of action of the mixture was intermediate between type A and type F alone, as assessed at 10 weeks, when there was a tendency of conserving the beneficial effect on one eye at the expense of t hat on the other. Although there was no apparent potentiation of the clinic al efficacy, the combination of these different types of toxin might be use d for decreasing the risk of antibody development.