The effect of cimetidine on meal-stimulated gastric function and exogenous pancreatic enzymes in cystic fibrosis.

Some patients with cystic fibrosis (CF) have malabsorption of fat and protein in spite of large amounts of supplemental pancreatic enzymes. This is partly due to acid inactivation of exogenous pancreatic enzymes in the stomach. The effect of cimetidine on gastric function and exogenous pancreatic enzymes was assessed by a marker perfusion technique in 4 CF children in a double-blind controlled fashion. Gastric acid secretion was higher in CF patients than in controls (P less than 0.005) and was reduced significantly by oral cimetidine (P less than 0.02). Rapid inactivation of exogenous trypsin and lipase occurred when gastric pH fell to less than 4.5. There was no loss of enzyme activity during treatment with cimetidine when gastric pH remained above 5.5. Activity of lipase and trypsin in the jejunum improved in all subjects. Fat and nitrogen absorption assessed by a balance technique during the study period showed a small improvement in fat absorption while on cimetidine. We conclude that some CF patients have a high meal-stimulated gastric acid output which causes inactivation of trypsin and lipase. Cimetidine was effective in reducing acid secretion in such patients and led to small improvements in fat absorption.