Cimetidine fails to suppress the rise in plasma secretin during fasting

The effects of cimetidine on plasma secretin were studied during prolonged fasting in order to determine whether gastric acid output influences secretin release under these circumstances. Twenty healthy volunteers starved for 36 h and were refed with oral glucose. They were given placebo or cimetidine (1.6 g daily) for 24 h before and during the starvation period. After 12 h fasting plasma secretin like immunoreactivity (SLI) was lower (P less than 0.02) in the cimetidine group than in the placebo group. After 36 h plasma SLI was higher (P less than 0.001) in both groups compared to the 12 h value but there was no statistically significant difference between the 2 groups. Refeeding caused prompt suppression of plasma SLI in both groups. Plasma gastrin was lower (P less than 0.001) after 36 h than 12 h in the placebo group only, but there was no significant difference between the groups. Blood glycerol (P less than 0.01) and 3 hydroxybutyrate (P less than 0.02) concentrations were higher after 36 h than after 12 h fasting in both groups. During fasting, sufficient to cause mobilisation of fat and ketosis, cimetidine failed to suppress plasma SLI. This may be due to inadequate suppression of gastric acid output or to some alternative stimulus to secretin release during fasting.