Inhibition of Histamine‐Stimulated Increases in Neart Rate in Man with the H₂‐Histamine Receptor Antagonist Cimetidine

Abstract

The influence of an H2‐histamine receptor antagonist, cimetidine, on histamine‐induced changes in heart rate and blood pressure was examined in a randomized double‐blind study in six fasted male subjects. The intravenous infusion of histamine (10 μg/min) for 20 minutes caused an immediate and sustained increase in heart rate (26 per cent and a transient fall in mean arterial blood pressure (10 per cent). Cimetidine pretreatment (300 mg intravenously) inhibited histamine‐elevated heart rate by 75 per cent (P < 0.05) and histamine‐decreased blood pressure by 54 per cent (P < 0.05). Cimetidine by itself did not cause significant changes in heart rate or blood pressure. These results illustrate that H2‐histamine receptor antagonists significantly inhibit histamine‐induced increases in heart rate in man and support the potential use of cimetidine in certain cases of tachyarrhythmia.

Inhibition of Acetylcholinesterase by Histamine Agonists and Antagonists

“…Moreover, bradycardia has also been reported after oral administration of therapeutic doses of cimetidine (Jeffreys & Vale 1978). This effect might still be attributed to acetylcholinesterase inhibition, although cimetidine may induce bradycardia via blockade of H2-receptors in the heart (Grund & Hunninghake 1981). Diarrhoea has been documented as a side effect of cimetidine (Fastner 1980;Cimetidine Package Insert 1983).…”

Letter to the Editor

“…The exact mechanism of H-2 antagonist-induced bradycardia is unknown. H-2 receptors have been found in sinus nodal tissues (Watkins et al 1979), and their antagonists decrease histamine-induced tachycardia (Grund & Hunninghake 1981).…”