Effects of botulinum toxin dilution with isolated lidocaine (without epinephrine) on injection pain and post-operative complications: pilot randomized clinical trial.

[INTRODUCTION] Pain and complications of botulinum toxin injection are important deterrents that may reduce patient satisfaction. Toxin attenuation via lidocaine (with or without epinephrine) might alleviate pain. Except a recent study, no study has assessed the effects of the incorporation of lidocaine alone (without epinephrine/additives) to botulinum toxin.

[METHODS] This pilot multicenter double-blind randomized placebo-controlled clinical trial was performed on 102 patients randomly divided into two groups of experimental (lidocaine without epinephrine) or control (normal saline). Patients received 100 units of botulinum toxin. In the experimental group, botulinum toxin was diluted with 1 ml of 2 % lidocaine without adrenalin; in the placebo group, botulinum toxin was diluted with 1 ml of normal saline. Pain was assessed after injection using a 11-point numerical rating scale '0-10'. Post-injection complications were assessed 24 h later based on patients' reports and surgeons' observations. Data were analyzed using Student t-test and Fisher exact test (α = 0.05).

[RESULTS] The groups were balanced in terms of age and gender ( > 0.05). The mean (SD) pain levels in the placebo and lidocaine groups were 3.70 ± 2.05 and 3.39 ± 1.78, respectively ( = 0.310, -test). Ptosis and diplopia were not observed in any groups. Asymmetry existed in 4 control subjects (8.7 %) and 5 experimental subjects (8.9 %) ( = 1.0, Fisher). In the control group, 12 patients needed retouch treatment (26.1 %); in the lidocaine group, 11 patients needed retouch therapy (19.6 %) (Fisher,  = 0.482).

[CONCLUSIONS] Dilution of botulinum toxin with lidocaine might not reduce injection pain or alter the incidence of the assessed complications after 24 h.