Assessment of beta blockade with propranolol

Each of seven subjects received on a weekly basis placebo or 10, 20, 40, 80, or 160 mg propanolol orally four times daily. The effect of propranolol on the resting heart rate and the heart rate response to the Valsalva maneuver, tilt, isoproterenol, and maximal exercise were measured. Coefficients of determination were calculated from the individual dose-response curves. The results indicate that the resting heart rate and the tachycardiac response to the Valsalva maneuver and tilt cannot be used to estimate beta blockade. Propranolol concentrations correlated well (mean r² = 0.80) with the isoproterenol dose ratio minus one, but isoproterenol challenges appear clinically inapplicable. Reduction in maximal exercise tachycardia correlated best with propranolol concentrations (mean r² = 0.89) but, to the extent that exercise could not be performed, there was no reliable way of clinically documenting beta blockade and only the serum concentration of propranolol was available as an indicator of appropriate therapy.