Vachiramon V.Tanratana P.Anuntrangsee T.Palakornkitti P.Yeesibsean N.Kungvalpivat P.Fabi S.Mahidol University2023-05-192023-05-192023-01-01Skin Research and Technology Vol.29 No.1 (2023)0909752Xhttps://repository.li.mahidol.ac.th/handle/20.500.14594/82635Background: 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.MedicineArticleSCOPUS10.1111/srt.132402-s2.0-851422280711600084636382669