Efficacy of botulinum toxin type a after topical anesthesia.

Purpose: To determine whether the use of topical anesthesia has an impact on botulinum toxin type A (BTX-A) efficacy.

Methods: Forty patients (20 receiving BTX-A for facial cosmetic rhytid reduction and 20 for benign essential blepharospasm) were evaluated in a double-blind, randomized, triple-crossover study at 2.5- to 4.5-month intervals. The discomfort and efficacy of BTX-A injections after betacaine application to half the face (random assignment) were compared against the discomfort and efficacy of a placebo ointment on the other half of the face. This was followed by cryoanalgesia to the entire face.

Results: Patients ranged from 27 to 81 years of age (mean, 53 years), and 34 were female. Of the 120 total injection comparisons, a better BTX-A effect on one side of the face was reliably identified by 80% and 77% of blepharospasm and cosmetic patients, respectively, with the placebo-treated side providing better BTX-A effect approximately 90% of the time (p < 0.001). Patients reported a more painful side during injection in just 18 of the 120 trials, and only 1 of 40 patients believed the administration of analgesia was worth the trouble.

Conclusions: Pretreatment with topical betacaine followed by skin cooling seems to have a deleterious impact on BTX-A effect without a significantly beneficial patient-perceived reduction in injection discomfort.