Effect of premedication on drug absorption and gastric emptying

The rate of paracetamol absorption after oral administration was used as a model of drug absorption and as an indirect measure of the rate of gastric emptying in 37 patients awaiting elective general surgery after different premedications. After saline (control) and diazepam, paracetamol absorption was normal but after morphine or nefopam, absorption was delayed markedly, presumably as a result of delayed gastric emptying. After naloxone there was a small but insignificant delay.