Safety and Efficacy of Vocacapsaicin for Management of Postsurgical Pain: A Randomized Clinical Trial.

BACKGROUND: Nonopioid management of postsurgical pain remains a major unmet need. Few studies have evaluated TRPV1 agonists for analgesia after surgery. We studied intraoperative vocacapsaicin, a novel prodrug of the TRPV1 agonist capsaicin, in a validated model of postsurgical pain.

METHODS: This was a triple-blinded, randomized, placebo-controlled, dose-ranging trial in patients undergoing bunionectomy. We randomized patients 1:1:1:1 to surgical site administration of 14 mL of placebo or one of three vocacapsaicin concentrations: 0.30, 0.15, or 0.05 mg/mL. The prespecified primary endpoint was the area-under-the-curve of the Numerical Rating Scale (NRS) pain score at rest through 96 hours for the 0.3 mg/mL group. Prespecified ordered, secondary endpoints for the 0.3 mg/mL group included percent of patients who did not require opioids from 0-96 hours, total opioid consumption through 96 hours, and the area-under-the-curve of the NRS pain score for the first week.

RESULTS: We randomized 147 patients. During the first 96 hours, vocacapsaicin 0.30 mg/mL reduced pain at rest by 33% vs. placebo (primary endpoint, 95% CI [10%, 52%], effect size (Cohen's D) = 0.61, p = 0.005). Twenty-six percent of patients receiving vocacapsaicin 0.30 mg/mL did not require postoperative opioids for analgesia (p=0.025) vs. 5% of patients receiving placebo. Vocacapsaicin 0.30 mg/mL reduced opioid consumption over the first 96 hours by 50% vs. placebo (95% CI [26%, 67%], effect size = 0.76, p = 0.002). Vocacapsaicin 0.30 mg/mL reduced pain over the first week by 37% vs. placebo (95% CI [12%, 57%], effect size = 0.62, p = 0.004). Treatment effect persisted for at least 2 weeks. All study endpoints showed an administered concentration vs. response relationship. Vocacapsaicin was well-tolerated with no differences between groups in any safety parameter.

CONCLUSIONS: A single, local administration of vocacapsaicin during surgery reduced pain and opioid consumption for at least 96 hours after surgery compared to control.

TRIAL REGISTRATION: ClinicalTrials.gov NCT03599089.