A double blind placebo-controlled study on the rectal administration of morphine as a premedication in abdominal hysterectomy

Abstract

Abstract Benzodiazepines are now commonly used as anxiolytic premedication prior to surgery. However, the role of opioids, as a premedication, has diminished over the last decades and they are no longer routinely used for premedication. Rather, opioids are generally used to treat severe pain in the postoperative period. Studies have shown that both NSAIDs and opioids improve analgesia in the early postoperative period. Until now, there have been no studies investigating the effect of morphine as a rectal premedication in adults in combination with blood levels of morphine. The effect of a rectal premedication with 30 mg of morphine sulphate, on postoperative pain levels and opioid consumption via intravenous patient controlled analgesia (PCA), was investigated in a double blind, placebo controlled study in 78 patients after abdominal hysterectomy (morphine group n =38; placebo group n =40). The cumulative consumption of opioid within the first four postoperative hours was 26% lower in the morphine group than in the placebo group (p=0.002). Patients in the morphine group also had less pain. The mean pain scores of all patients premedicated with morphine were significantly lower compared with the placebo group during the entire postoperative period (until the first postoperative morning) (p = 0.013). Neither opioid consumption nor the incidence of opioid-related side effects differed between the two groups. Pharmacokinetic data were determined in seven of these patients: 270 minutes after administration of rectal morphine the mean morphine plasma concentration was above the therapeutic threshold of 10–30 ng cc −1 . However, the kinetic data showed considerable interindividual variability; t max ranged from 30 minutes in three patients to 90 minutes in four patients after administration of the suppository and C max varied from 24.0 to 75.2 ng cc −1 (mean 46.9 ± 19.9 ng·cc −1 ). In conclusion, rectal morphine as a premedication in patients prior to abdominal hysterectomy, leads to reduced pain scores and increased efficacy of postoperative PCA within the early postoperative period, without increasing opioid-related side effects.