Speed of onset of pharmacodynamic activity of propranolol, practolol, oxprenolol and metoprolol after intravenous infection in man.

1 The speed of onset of the pharmacodynamic activity of intravenous propranolol, practolol, oxprenolol and metoprolol was determined, using attenuation of isoprenaline-induced tachycardia as the end-point, in 16 patients with clinically coronary heart disease. 2 Antagonism was evident within 15 s of injection into the central circulation of all four drugs. The time to maximum attenuation of isoprenaline tachycardia was significantly more rapid with propranolol and oxprenolol than with practolol and metoprolol.