Reduced β‐adrenoceptor sensitivity in the elderly

Abstract

The effect of age on sensitivity to both isoproterenol and propranolol has been investigated in 27 male volunteers aged 21 to 73 yr. The dose of isoproterenol (given as a rapid intravenous injection) required to increase the resting heart rate by 25 bpm (I 25 ) increased with age. The I 25 was repeated during an intravenous infusion of propranolol and the dose ratio (I 25 after propranolol divided by the control I 25 ) determined. This was related to the concentration of free propranolol in plasma. It was found that the effectiveness of any given free concentration diminished progressively with age. These data are consistent with a diminished responsiveness of the β‐adrenoceptor to both agonist and antagonist drugs with advancing years.