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Beta‐adrenergic receptors in the elderly are not less sensitive to timolol
Author(s) -
Klein Catherine,
Gerber John G,
Gal Joseph,
Nies Alan S
Publication year - 1986
Publication title -
clinical pharmacology and therapeutics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.941
H-Index - 188
eISSN - 1532-6535
pISSN - 0009-9236
DOI - 10.1038/clpt.1986.158
Subject(s) - timolol , propranolol , chemistry , pharmacology , adrenergic beta antagonists , adrenergic receptor , medicine , endocrinology , receptor , intraocular pressure , ophthalmology
The elderly have been reported to be less sensitive to the β‐adrenergic blocking effect of propranolol. However, propranolol is a racemate, and age‐related changes in stereoselective metabolism or protein binding could confound interpretation of the data. To avoid these problems, we studied timolol in 12 young and 12 elderly healthy subjects. The dose of isoproterenol required for a heart rate increase of 25 bpm (I 25 ) was determined before and 2 hours after an oral 10 mg dose of timolol. A dose ratio (DR) was calculated for each subject as the I 25 after timolol/I 25 before timolol. The binding constant for timolol binding to the receptor was calculated as the plasma timolol concentration ÷ (DR − 1). The I 25 for the elderly group was significantly greater than the I 25 for the young group, but the timolol binding constant was the same for both groups. We conclude that, although the elderly are less sensitive to isoproterenol, they are not less sensitive to timolol, and thus our data do not implicate a change in the interaction of β‐adrenoceptors with antagonists. Clinical Pharmacology and Therapeutics (1986) 40, 161–164; doi: 10.1038/clpt.1986.158