The effects of cimetidine on serum calcium and parathyroid hormone levels in primary hyperparathyroidism.

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Abstract
1 Cimetidine has been reported to reduce serum calcium and parathyroid hormone (PTH) levels in primary hyperparathyroidism, but some studies have reported negative findings. 2 A double‐blind, controlled trial of cimetidine in this condition was, therefore, conducted. Eight patients were given cimetidine and placebo for 2 months each, in random order. Only one patient showed a significant fall in serum calcium on cimetidine and no patient showed a fall in PTH levels. 3 In addition, eight patients were studied during a 48 h continuous intravenous infusion of cimetidine. The first five patients exhibited no effect of the drug on either calcium of PTH levels, but in the sixth there appeared to be a dose‐dependent suppression of PTH. The seventh and eighth patients were, therefore, given a higher dose of the drug but it failed to suppress calcium or PTH values. 4 It is concluded that cimetidine is not of value in primary hyperparathyroidism.