Doubleblind randomized study performed with 4% lidocaine cream and vehicle in the application of type A botulinum toxin: analysis of the pain during the procedure and of the interference with the efficacy and duration of the effect

Introduction: For some patients, pain during the injection of botulinum toxin can represent a limitation for performing the procedure. There are doubts about whether the use of topical anesthetic decreases pain or interferes with the treatment's efficacy and duration of effect. Objectives: To study the effect of 4% lidocaine cream in controlling pain during BoNT-A - Speywood Unit botulinum toxin application, comparing it to the vehicle. In addition, the study was aimed at verifying whether the cream influences the treatment's outcome and duration. Methods: An experimental, prospective, double-blind, randomized study was carried out. The pain was assessed through a compartmentalized numerical rating scale (CNRS). The effect was assessed through a four-point contraction qualitative scale. Results: After evaluating the pain scale, higher values were observed in the placebo group when compared to the group that used anesthetic, with statistical significance. Furthermore, there was no statistical difference in the efficacy and duration of effect over weeks 4, 8, 12, and 16. Conclusions: BoNT-A - Speywood Unit toxin was effective and safe for the treatment of glabellar and frontal wrinkles. The use of topical anesthetics (4% lidocaine cream) reduced the pain during the procedure. In addition, there was no interference in the toxin's efficacy and effect duration.

Keywords: BOTULINUM TOXIN TYPE A, LIDOCAINE, PAIN, THERAPY.