PERIPHERAL MORPHINE ANALGESIA IN DENTAL SURGERY

The recent identification of opioid receptors on peripheral nerve endi ngs of primary afferent neurons and the expression of their mRNA in do rsal root ganglia support earlier experimental data about peripheral a nalgesic effects of locally applied opioids. These effects are most pr ominent under localized inflammatory conditions. The clinical use of s uch peripheral analgesic effects of opioids was soon investigated in n umerous controlled clinical trials. The majority of these have tested the local, intraarticular administration of morphine in knee surgery a nd have demonstrated potent and long-lasting postoperative analgesia. As the direct application of morphine into the pain-generating site of injury and inflammation appears most promising, we examined direct mo rphine infiltration of the surgical site in a unique clinical model of inflammatory tooth pain. Forty-four patients undergoing dental surger y entered into this prospective, randomized, double-blind study. Befor e surgery they received, together with a standard local anesthetic sol ution (articaine plus epinephrine) a submucous injection of either 1 m g of morphine (group A) or saline (group B). Postoperative pain intens ity was assessed using the visual analog scale (VAS) and numeric ratin g scale (NRS) at 2, 4, 6, 8, 10, 12, 16, 20 and 24 h after surgery. in addition, patients recorded the occurrence of side effects and the su pplemental consumption of diclofenac tablets. Results of 27 patients w ere analyzed (group A: n = 14, group B: n = 13). Pain scores which wer e moderate to severe preoperatively were reduced to a similar extent i n both groups up to 8 h postoperatively. Thereafter, pain scores in gr oup A were significantly lower than those in group B for up to 24 h, d emonstrating the analgesic efficacy of additional morphine. The time t o first analgesic intake and the total amount of supplemental diclofen ac were less in group A than in group B. No serious side effects were reported. Our results show that 1 mg of morphine added to a local anes thetic for dental surgery results in significant improvement of postop erative analgesia. Since the majority of dental surgeries is accompani ed with an inflammatory reaction, supplemental morphine may be of bene fit for the relief of postoperative dental pain. (C) 1998 Internationa l Association for the Study of Pain. Published by Elsevier Science B.V .