Assessment of alpha- and beta-adrenoceptor blocking actions of labetalol.
Isoprenaline dose-response curves plotting increases in heart rate before and after labetalol are suggestive of competitive antagonism at beta-adrenoceptor sites. Phenylephrine dose-response curves using increases in systolic pressure before and after labetalol are suggestive of competitive antagonism at alpha-adrenoceptor sites. The ratio of alpha:beta-adrenoceptor antagonism induced by labetalol is approximately 1:3. Peak pharmacological responses after a single oral dose of labetalol (400 mg) occurred between 90-120 min after administration.
D000317:Adrenergic alpha-Antagonists; D000319:Adrenergic beta-Antagonists; D000328:Adult; D001794:Blood Pressure / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004983:Ethanolamines / Q000494:pharmacology*; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D007545:Isoproterenol / Q000037:antagonists & inhibitors; D007741:Labetalol / Q000494:pharmacology*; D008297:Male; D010656:Phenylephrine / Q000037:antagonists & inhibitors
D000317:Adrenergic alpha-Antagonists; D000319:Adrenergic beta-Antagonists; D004983:Ethanolamines; D010656:Phenylephrine; D007545:Isoproterenol; D007741:Labetalol