The Analgesic Efficacy and Safety of Intra-Articular Morphine and Mepivicaine Following Temporomandibular Joint Arthroplasty

Purpose: This study was designed to evaluate the efficacy and safety of intra-articular morphine, mepivacaine, or a combination of both in the management of temporomandibular joint (TMJ) pain in a 24-hour period after arthroplasty. Patients and Methods: This was a randomized, double-blind, prospective, parallel, placebo-controlled, single-injection study of 35 patients who underwent TMJ arthroplasty. Patients were randomized into 4 groups. Group M (morphine) received 1 mg of morphine sulfate in 1 mL of saline; group MEP (mepivicaine) received 30 mg of mepivacaine hydrochloride in 1 mL of saline; group M/MEP received 30 mg of mepivacaine hydrochloride and 1 mg of morphine in 1 mL of saline; and group C (saline control) received 1 mL of saline. Patients received a single dose of study medication when their postoperative pain reached a moderate or severe intensity and was 50 mm or greater on a 100-mm pain scale. Analgesic efficacy measures included the time to meaningful pain relief measured using a stop watch and time to rescue medication. Pain relief and pain intensity ratings were recorded at the time to relief and time to rescue medication. A global evaluation for the effectiveness of the medications was recorded within 24 hours after dosing. Adverse events were recorded and categorized by system effect. Results: MEP and M/MEP were significantly more effective than placebo for all the analgesic measures. Morphine alone provided only mild analgesia and did not differ from placebo in the primary efficacy measures. The average overall pain relief was substantially better for MEP than M and M/MEP (P = .03). In patients receiving MEP, the mean time to pain relief was 2.9 minutes and the mean analgesic duration was 9.7 hours (586 minutes); 3 patients required no rescue medication in the 24 hour postdosing period. In patients receiving M/MEP, the mean time to analgesia was 7.6 minutes and the duration of analgesia was 2.7 hours (175 minutes). The average time to onset and duration of analgesia in the MEP and M/MEP groups was statistically significantly better (P < .001) then in the M alone group (17.7 minutes, 0.43 hours, respectively) and the placebo C group (16.1 minutes, 0.17 hours, respectively). At the end of the study, 80% of the patients given MEP rated the medication as a very good or excellent pain reliever, whereas only 40% of patients given M/MEP, 10% of patients given M, and no patients given placebo gave these same ratings. No serious adverse events occurred in this study. Gastrointestinal adverse events were the most common side effect noted in the MEP and M/MEP groups but were mild in intensity and reversed without treatment. Conclusion: All intra-articular TMJ injections of active substances provided better analgesia than placebo. Morphine alone provided only mild and short-acting analgesia. The local anesthetic, mepivacaine, given alone was safe, provided the quickest, longest acting and most effective analgesia. This proof of concept study suggests that local anesthetics are superior analgesics when given intra-articularly for postoperative TMJ surgery pain and should be investigated for dose response and multiple or continuous infusion effectiveness.