Postoperative absorption of controlled-release morphine sulphate. A study in patients given no parenteral opioids.

The absorption of morphine sulphate in a controlled-release formulation was studied in 12 patients who had undergone unilateral inguinal hernia repair under a light general anaesthetic and ilio-inguinal block. Serum morphine concentrations were measured serially and gastric emptying was assessed by measurement of paracetamol absorption. Three patients had delayed gastric emptying and impaired morphine absorption in the immediate postoperative period. Four hours later, there was a significant reduction in gastric emptying in eight patients who had normal paracetamol and morphine absorption in the immediate postoperative period.