The dose-response effects of oral cimetidine on gastric pH and volume in children

The effects of preanesthetic oral cimetidine on gastric fluid pH and volume were studied in 97 infants and children. A dose-response curve was constructed using doses of 2.5, 5.0, 7.5, and 10 mg/kg. The ED50 of cimetidine that produces pH values higher than 2.5 was 3.0 mg/kg, and the ED95 was 7.5 mg/kg. Cimetidine exponentially reduced the volume of gastric fluid. Cimetidine was most effective between one and four hours after oral administration. In children who are at high risk of pulmonary aspiration, we recommend that oral cimetidine, 7.5 mg/kg, be given 1-3 hours preoperatively in order to protect the lungs from the accidental aspiration of acidic gastric secretions.