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 injection. To minimize the risk, mixing different types of toxin might reduce the antigenic presentation of a specific toxin and associated proteins. At the same time, inhibition of the neuromuscular release process at the multiple 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 toxins 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 each) on one side and either type A or F toxin on the other side of the orbicularis oculi muscle. Clinical evaluation at 4 and 10 weeks after the injection 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 that on the other. Although there was no apparent potentiation of the clinical efficacy, the combination of these different types of toxin might be used for decreasing the risk of antibody development.