Morphine-induced seizures in newborn infants

Two neonates suffered from generalized seizures during the course of intravenous morphine sulfate for post-operative analgesia. They received morphine in doses of 32 micrograms/kg/hr and 40 micrograms/kg/hr larger than a group of 10 neonates who received 6-24 micrograms/kg/hr and had no seizures. Plasma concentrations of morphine in these neonates was excessive (60 and 90 mg/ml). Other known reasons for seizures were ruled out and the convulsions stopped a few hours after cessation of morphine and did not reoccur in the subsequent 8 months. It is suggested that post-operative intravenous morphine should not exceed 20 micrograms/kg/ml in neonates.