Intestinal calcium transport: effect of cimetidine.

Recently cimetidine (Tagamet), a widely used drug for peptic ulcer disease, was found to decrease serum levels of calcium and immunoreactive parathyroid hormone in patients with hyperparathyroidism. Since parathyroid hormone action is closely related to calcium homeostasis, we studied the effect of cimetidine on intestinal calcium transport. An in vivo perfusion technique was used for the study of net transport and lumen to mucosa flux of 45calcium. Our results indicate a significant decrease in net calcium transport and lumen to mucosa flux of 45calcium in the rats injected with cimetidine, compared to control rats. Direct addition of cimetidine to the perfusion solution did not alter transport rates significantly. The mechanism by which cimetidine affects calcium transport may be secondary to its effect on the release of parathyroid hormone from the parathyroid gland or an effect on vitamin D metabolism.