Does cimetidine alter the cardiac response to exercise and propranolol?

The recent discovery of histamine (H) receptors in the heart raises the possibility that the H2-antagonist drug, cimetidine, used in the therapy of peptic ulcer, might have cardiac side-effects and might impair the cardiac response to exercise. In 10 normal subjects, cimetidine did not alter the normal heart rate and blood pressure response to treadmill exercise, nor was the effect of beta-blockade by propranolol exaggerated. Thus it appears that the use of propranolol is not necessarily a contraindication to cimetidine therapy, or vice versa. However, further trials on patients with ischaemic heart disease are required to exclude any additive effects of cimetidine and propranolol on the diseased heart.