Reversing the Effects of 0.5% Bupivacaine Using Phentolamine Mesylate: A Preliminary Randomized Controlled Clinical Trial.

Phentolamine mesylate is the only commercially available dental local anesthetic reversal agent. It has been proven safe and effective for reversing most local anesthetics used in dentistry but was never tested with bupivacaine. The aim of this project was to evaluate the effectiveness of 0.4-mg phentolamine mesylate in reversing an inferior alveolar nerve block (IANB) with 0.5% bupivacaine, 1:200,000 epinephrine. Sixty-six participants were recruited and were administered an IANB with bupivacaine. After confirmation of anesthesia, they were randomized into 1 of 2 groups (phentolamine mesylate or control). Participants in the phentolamine mesylate group received a second injection with 1.7-mL OraVerse (0.4-mg phentolamine mesylate), while participants in the control group received a second injection with 1.7-mL sterile saline water. Participants were trained to self-assess sensation (lower lip and tongue) and function (drinking, speaking, and smiling), which they did every 20 minutes, and they recorded the time when sensation/function returned to normal. Comparative analysis was completed using independent sample t-tests, univariate linear regressions, and Pearson chi-square. Forty-three participants were randomized, and 34 completed the study (phentolamine mesylate, n = 15; control, n = 19). There was a statistically significant difference between the 2 treatment groups for return of normal sensation to the lower lip (mean difference of 2 hours and 17 minutes; P = .027) and the tongue (mean difference of 1 hour and 35 minutes; P = .046) in favor of the phentolamine mesylate group. The results indicate that phentolamine mesylate hastens the return to normal sensation of an IANB with bupivacaine.