March 1972

Effect of Atropine on the Tachycardia of Hyperthyroidism

Author Affiliations


From the Division of Clinical Pharmacology, Department of Pharmacology (Dr. Crout), and the Department of Surgery (Dr. Heimbach), University of Texas Southwestern Medical School at Dallas. Dr. Crout is now with the Bureau of Drugs, Food and Drug Administration, Rockville, MD.

Arch Intern Med. 1972;129(3):430-432. doi:10.1001/archinte.1972.00320030050004

Dose-response curves for the effect of atropine sulfate on heart rate were determined in six hyperthyroid and six euthyroid subjects. Both groups responded to atropine in a qualitatively similar manner, but a smaller increase in heart rate was produced by atropine in the hyperthyroid group. The data are interpreted as suggesting that the resting tachycardia of hyperthyroidism is due to the combination of a direct rate-increasing effect of thyroxine on the sinoatrial (SA) node and an impairment of vagal inhibition of heart rate.