Meptazinol and Morphine in Postoperative Pain Assessed with a New Method for Onset and Duration

Publisher Website
Google Scholar
Abstract
Meptazinol, m‐(3‐ethyl‐1‐methyl‐hexahydro‐1‐H‐azepin‐3‐yl) phenol hydrochloride is a centrally active opioid analgesic with a specificity for the mu‐1 receptor. It has been reported to lack many of the side effects commonly observed with morphine and morphinelike drugs in man. The objective of this study was to assess the analgesic efficacy and safety of meptazinol (50 mg and 100 mg) relative to morphine (5 mg and 10 mg) when administered intramuscularly for the treatment of postoperative pain, in addition, a new clinical method for measuring onset and duration and a statistical technique for evaluating the study data are presented. One hundred and seventeen patients were evaluated for 6 hours in G randomized double blind, single dose, parallel‐groups trial. Estimates of relative potency for hourly pain and relief parameters, and the summary variables sum of pain intensity differences (SPID) and total pain relief (TOTPAB) were performed. The estimate of relative potency of meptazinol to morphine for pain relief was 0.19 at ½ hour (i.e. 100 mg of meptazinol was approximately equivalent to 20 mg of morphine). Thereafter, there was a rapid decline of efficacy for meptazinol, with a relative potency estimate of 0.12 at 1 hour and 0.06 at 2 hours. The distribution functions for several time related events were estimated including time to onset, duration and time to remedication. The two drugs had approximately equal onset, but meptazinol had significantly shorter duration. More patients on meptazinol required remedication with a rescue analgesic and at an earlier time than patients on morphine. The incidence of adverse effects was highest for meptazinol 100 mg. In summary, the study showed that intramuscular meptazinol is an analgesic with onset of relief as rapid as that of morphine but with much shorter duration. Because of its short duration of effect, meptazinol at 50 mg may be considered a candidate for use in ambulatory surgical procedures if further studies show the drug is well tolerated at this dose.