Comparison of two botulinum-toxin preparations in the treatment of essential blepharospasm.

A double-blind study was performed on 212 consecutive patients (58 men, 154 women) with essential blepharospasm, who received one injection of Botox and one injection of Dysport in two separate treatment sessions (at the first session the patients randomly received one of the drugs, at the second the other drug was given. The patients' mean age was 66.4 years +/- 8.14 (range 39-86 years). The average dose of Botox per treatment was 45.4 IU +/- 13.3 (range 25-85 IU) and of Dysport 182.1 IU +/- 55.1 (range 100-340 IU). We used an empirical ratio Botox:Dysport of 1:4 (IU) in order to ensure equal doses. All patients had received botulinum toxin injections prior to the present study (mean 15.3 injections +/- 9.4; range 1-43 injections). The effect of Botox lasted 7.98 weeks +/- 3.8 (range 0-16 weeks), while the effect of Dysport lasted 8.03 weeks +/- 4.6 (range 0-22 weeks). Side effects (ptosis, tearing, blurred vision, double vision, hematoma, foreign body sensation) were observed with Botox in 36 of 212 (17.0%) of the treatment sessions and with Dysport in 51 of 212 sessions (24.1%). Ptosis was observed with Botox in 3 cases (1.4%) and with Dysport in 14 cases (6.6%). There was no statistically significant difference in the duration of the treatment effect between the two preparations (P = 0.42). The total number of side effects was lower with Botox than with Dysport; the significance of the difference was moderate (P < 0.05). However, the rate of occurrence of ptosis was significantly lower with Botox (P < 0.01). The bioequivalence, which varies between 1:3 and 1:6 (Botox:Dysport) in the literature, was found to be 1:4 in this study.