Labetalol-d5 is intended for use as an internal standard for the quantification of labetalol by GC- or LC-MS. Labetalol is an adrenergic receptor (AR) antagonist.1 It inhibits agonist-induced contraction of rabbit aortic strips, decreases in contractile force in isolated guinea pig atria, and vasorelaxation in isolated guinea pig tracheal strips (pA2s = 6.99, 7.68, and 7.54, respectively), tissues that endogenously express high levels of α-, β1-, and β2-ARs, respectively. Labetalol (2.5-25 mg/kg) reduces blood pressure in spontaneously hypertensive rats. It reduces blood pressure in DOC-salt rats, two-kidney Goldblatt rats, and one-kidney dogs. Labetalol (5 mg/kg) reduces infarct size in a dog model of myocardial infarction induced by occlusion of the left anterior descending artery. Topical administration of labetalol (0.25-1% v/v) reduces intraocular pressure in rabbits. Formulations containing labetalol have been used in the treatment of hypertension.
1.Baum, T., and Sybertz, E.J.Pharmacology of labetalol in experimental animalsAm. J. Med.75(4A)15-23(1983)