Botulinum toxin therapy of cervical dystonia: comparing onabotulinumtoxinA (Botox®) and incobotulinumtoxinA (Xeomin ®).

Several botulinum toxin (BT) drugs are licensed for the treatment of cervical dystonia (CD). We wanted to compare the efficacy and the potency labelling of incobotulinumtoxinA (Xeomin^®)  and onabotulinumtoxinA (Botox^®) by analysing the duration of their therapeutic effect in a cross-over study. For this we studied 40 CD patients (26 females, 14 males, age at therapy onset 52.6 ± 12.0 years, duration of dystonia at therapy onset 10.0 ± 9.2 years, Tsui score 9.1 ± 3.9) who first received Botox^® and then Xeomin^® for at least 4 injection series each. BT doses were exchanged based on a 1:1 conversion ratio. Altogether 1,101 treatment cycles were evaluated. For each patient 27.5 ± 13.1 treatment cycles were recorded. Patients received 18.4 ± 12.4 treatment cycles with Botox^® and 9.2 ± 4.5 with Xeomin^®. The treatment duration (TD) throughout the treatment course was 11.3 ± 1.0 weeks (Botox^® 11.2 ± 1.1 weeks, Xeomin^® 11.4 ± 1.3 weeks). The interinjection interval (II) throughout the treatment course was 14.8 ± 1.9 weeks (Botox^® 14.7 ± 1.6 weeks, Xeomin^® 15.0 ± 2.2 weeks). The mean difference between Botox^® and Xeomin^® was 0.3 weeks for TD (two-sided 95 % confidence interval [-0.3; 0.9]) and 0.5 weeks for II (two-sided 95 % confidence intervals [-0.4; 1.4]). The confidence intervals of both parameters were within the predefined therapeutic equivalence range set to ±1.5 weeks, thus indicating similar efficacy of both BT drugs. Having based the exchange of Botox^® and Xeomin^® on a conversion factor of 1:1 our data confirm previous findings of an identical potency labelling of both products, thus allowing comparisons of efficacy, adverse effects and costs.