Rectally Administered Morphine: Plasma Concentrations in Children Premedicated with Morphine in Hydrogel and in Solution

Seventeen healthy children undergoing eye surgery in general anaesthesia were given morphine rectally for premedication. Six patients (Group I) were given morphine 0.15 mg X kg-1 in a propylene glycol solution also containing diazepam and hyoscine. Eleven patients (Group II) were given morphine 0.5 mg X kg-1 in a starch hydrogel preparation. The plasma concentrations of morphine (Groups I and II) and diazepam (Group I) were studied. After the lower dosage of morphine the plasma concentrations never exceeded 10 ng X ml-1, whereas the mean peak plasma concentration was 25.3 +/- 5.5 ng X ml-1 after the higher dosage. One child in each of Groups I and II needed postoperative analgesics. The simultaneous plasma concentration of morphine was then lower than 5 ng X ml-1. Postoperative nausea occurred to about the same extent in both groups. It is suggested that morphine given rectally in a starch hydrogel may be an alternative to oral and parenteral routes of administration.