The influence of cimetidine on basal gastro-oesophageal sphincter pressure, intargastric pH, and serum gastrin concentration in normal subjects.

A pressure and pH-sensitive probe has been constructed for simultaneous measurement of gastro-oesophageal sphincter pressure and intragastric pH. The coefficient of variation for measurements of the gastro-oesophageal sphincter was 0.24, and for the intragastric pH, 0.09. After peroral ingestion of 400 mg of cimetidine or placebo, simultaneous measurements of gastro-oesophageal sphincter pressure and intragastric pH were made at fixed time intervals, and at the same time blood samples were taken for determination of serum gastrin and serum cimetidine concentrations. No demonstrable difference was found in the time-course of the gastro-oesophageal sphincter pressure after ingestion of cimetidine or placebo. After ingestion of cimetidine a significant rise in intragastric pH (p less than 0.05) occurred after 40 min, and this increased pH was maintained for the remainder of the experimental period, corresponding to a serum cimetidine concentration of over 1.00 mg/l. Similarly, there was a significant rise (p less than 0.05) in serum gastrin concentration after 150 min. There was a significant direct correlation between corresponding measurements of intragastric pH and serum gastrin (p less than 0.001), between intragastric pH and serum cimetidine (p less than 0.001), and between serum gastrin and serum cimetidine (p less than 0.05). Ingestion of cimetidine results in an increase in the serum gastrin concentration in healthy subjects, presumably as a result of reduced secretion of acid in the stomach. Neither the endogenous increase in serum gastrin concentration nor the increase in intragastric pH causes alteration in the gastro-oesophageal sphincter pressure.