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Plasma timolol levels and systolic time intervals
Author(s) -
Singh Bramah N,
Williams Faith M,
Whitlock Ralph M L,
Collett John,
Chew Christopher
Publication year - 1980
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.1980.145
Subject(s) - timolol , propranolol , potency , medicine , anesthesia , coronary artery disease , clinical pharmacology , cardiology , pharmacology , chemistry , glaucoma , ophthalmology , biochemistry , in vitro
The β‐blocking potency of timolol was compared with that of propranolol under steady‐state conditions in eight healthy subjects. The effects on systolic time intervals in healthy subjects and patients (n = 6) with coronary artery disease were evaluated in relation to varying timolol dose schedules and plasma concentrations. The β‐blocking potency was assessed by the inhibition of exercise‐induced tachycardia. Timolol was eight times as potent as propranolol. There was wide between‐patient variation (2.6 to 13.8) in timolol plasma concentration, and correlation between dose and peak (r = 0.61, p < 0.01) or nadir (r = 0.5, p < 0.01). There was a relatively weak correlation between timolol plasma concentration and degree of β‐blockade (r = 0.45, p < 0.05) and a linear correlation with dose (r = 0.98, p < 0.001). In healthy subjects timolol and propranolol had variable effects on systolic time intervals but in patients with coronary artery disease equipotent doses prolonged the preejection period, isovolumetric contraction time, and the ratio of the preejection period over the left ventricular ejection time. In patients as well as in normal subjects, the data indicated considerable β‐blocking effects for both drugs at the end of a 12‐hourly dosing schedule, suggesting that twice‐daily timolol and propranolol may be clinically practical. Clinical Pharmacology and Therapeutics (1980) 28, 159–166; doi: 10.1038/clpt.1980.145