The role of topical capsaicin gel in pain management during microfocused ultrasound treatment for neck laxity

BACKGROUND: The transient receptor potential vanilloid 1 (TRPV1) provides a heat and pain sensation (nociception). Capsaicin, a TRPV1 agonist, has been shown to induce a refractory period in the nerve terminal expressing TRPV1 and create long‐term nerve terminal defunctionalization. OBJECTIVE: To evaluate the efficacy of capsaicin for pain reduction during microfocused ultrasound with visualization (MFU‐V) treatment. METHODS AND MATERIALS: A randomized, split‐side study including 24 subjects was conducted. A combined 0.025% capsaicin gel and topical anesthetic were randomly applied on one side of the neck, and a topical anesthetic monotherapy was applied on the contralateral side for 30 min before MFU‐V treatment. Pain score (visual analog scale, 0–10) was evaluated at T1 (before MFU‐V), T2a (after the 4.5‐mm transducer treatment), T2b (after the 3.0‐mm transducer treatment), and T3 (after the entire treatment). Side effects were recorded. RESULTS: Mean pain scores at T2a for combined and single regimens were 5.19 (±2.26) and 6.91 (±1.72), respectively (p < 0.001). The capsaicin‐treated side had a lower pain score at T2b and T3 (p < 0.001). Redness was longer on the capsaicin‐treated side (112.67 vs. 10.68 min, p < 0.001). No other adverse events including contact dermatitis were reported. CONCLUSION: A single application of a combined 0.025% capsaicin gel with topical anesthesia produces a significantly lesser pain score during the MFU‐V treatment. Defunctionalization of TRPV1 may explain the alleviation of painful sensations caused by heat from MFU‐V.