Reduced β‐adrenoceptor sensitivity in the elderly

TLDR

The study measured the isoproterenol dose needed to raise heart rate by 25 bpm in 27 men aged 21–73, repeated during propranolol infusion, and related the dose ratio to free propranolol plasma concentration. Older men required higher isoproterenol doses to raise heart rate by 25 bpm, and the potency of free propranolol decreased with age, indicating reduced β‑adrenoceptor responsiveness 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.