Effects of glycopyrrolate and cimetidine on gastric volume and acidity in patients awaiting surgery.

Glycopyrrolate or cimetidine was administered before operation to patients undergoing elective surgery. After the induction of anaesthesia, the stomach contents were retrieved and the volume and pH measured. Neither drug diminished the volume of gastric contents compared with control. Glycopyrrolate produced little diminution in hydrogen ion concentration. Cimetidine caused a marked increase in pH with a mean [h+] 3.2 x 10(-3) g litre-1 compared with 1.4 x 10(-2) g litre-1 in the controls and 1.1 x 10(-2) g litre-1 in the glycopyrrolate group. Seventy-seven per cent of the patients receiving cimetidine had a pH greater than 2.5.