Topical Transdermally Delivered Lidocaine and Benzocaine Compared to Compounded Lidocaine/Tetracaine During Microfocused Ultrasound With Visualization Treatment.

Objective: The efficacy of various pre-medication strategies for comfort management during microfocused ultrasound with visualization (MFU-V) treatment has not been studied. The present objective was to compare 2 topical analgesics (lidocaine 4% and benzocaine 20%) formulated with a novel transdermal delivery system with compounded lidocaine 23%/tetracaine 7% (23/7) to mitigate discomfort during MFU-V treatment.

Methods: This was a randomized, double-blinded, split-face study. One hour before MFU-V, subjects (N=14 females) received 50 mg IM meperidine/25 mg IM promethazine/5 mg oral diazepam. Fifteen minutes before treatment, 1 side of the face was treated with 1 application of 4% lidocaine, followed by 1 application of 20% benzocaine; the contralateral side was treated with 2 applications of 23/7 (to maintain blinding). Numbness was assessed by blinded evaluator (scale: 1=completely numb to 4=not numb) pre-treatment. Subject pain scores (scale: 0=no pain to 10=worst pain) were collected post-treatment. Adverse events and subjective clinician measures were also assessed.

Results: Mean subject pain scores for 23/7 and lidocaine 4%/benzocaine 20% were 5.6 and 5.7, respectively. Mean numbness scores were similar for 23/7 (2.5) and lidocaine 4%/benzocaine 20% (3.0). Clinicians rated both products as "very easy" to apply. For lidocaine 4%/benzocaine 20%, 7.1% of subjects required no pauses during treatment, vs 14.3% for 23/7. However, more subjects required 4+ pauses with 23/7 (21.4% vs 7.1%). Lidocaine 4%/benzocaine 20% was preferred by 78.5% of subjects; 35.7% rated lidocaine/benzocaine 20% 4% as "Very Effective" vs 7.1% for 23/7. No adverse events were reported.

Conclusions: Lidocaine 4% and benzocaine 20% formulations utilizing a novel transdermal delivery system perform similarly to compounded lidocaine 23%/tetracaine 7% for discomfort mitigation during MFU-V treatment. More subjects preferred lidocaine 4%/ benzocaine 20% and rated it as "very effective" vs the compounded product. Fewer treatment pauses due to patient discomfort when using the lidocaine 4%/benzocaine 20% may translate to time efficiency. J Drugs Dermatol. 2018;17(7):729-734.