Comparison of the Efficacy of OnabotulinumtoxinA and AbobotulinumtoxinA at the 1:3 Conversion Ratio for the Treatment of Asymmetry after Long-Term Facial Paralysis

Background: Botulinum toxin A injection into the nonparalyzed side is used to treat asymmetry resulting from facial palsy. OnabotulinumtoxinA and abobotulinumtoxinA units are not equivalent. The authors compared the conversion ratio of 1:3 in patients with facial palsy. Methods: Fifty-five patients (age, 16 to 67 years; 43 women) with longstanding facial palsy were randomly treated with either onabotulinumtoxinA (n = 25) or abobotulinumtoxinA (n = 30) injections into the nonparalyzed side. Adverse effects, facial symmetry, subjective satisfaction, and Facial Disability Index were assessed after 1 and 6 months. Results: The incidence of adverse effects was higher with abobotulinumtoxinA (93.3 percent versus 64.0 percent; p = 0.007). Clinical scores of the nonparalyzed side decreased after 1 month and increased again at 6 months, with no between-group differences. Scores of the paralyzed side were lower in the onabotulinumtoxinA group before treatment, but similar in both groups thereafter. The paralyzed side scores increased after 1 month, and at 6 months were still higher than the pretreatment scores in both groups. Subjective assessment improved at all time points compared with pretreatment scores and differed between the two groups only at 1 month, when the abobotulinumtoxinA group was a bit too paralyzed. The physical function and social/well-being function subscales of the Facial Disability Index did not differ between the two groups. Conclusions: Both toxins efficiently reduced asymmetry in patients with facial palsy. Adverse effects were higher with abobotulinumtoxinA at an equivalence ratio of 1:3.