Pharmacotherapeutic Group: Labetalol hydrochloride is an alpha and beta blocking agent. ATC Code: C07AG01.
Pharmacology: Pharmacodynamics: Mechanism of Actions: Labetalol hydrochloride combines both selective, competitive alpha 1-adrenergic blocking and non-selective, competitive beta-adrenergic blocking activity in a single substance.
Labetalol hydrochloride contributes to a decrease in blood pressure in hypertensive patients. It produces dose-related (at usual doses) falls in blood pressure without reflex tachycardia and without significant reduction in resting heart rate, presumably through a mixture of its alpha-blocking effects and beta-blocking effects. Labetalol hydrochloride effectively reduces blood pressure in the standing or supine position, but because of the drug's alpha 1-receptor blocking activity; labetalol hydrochloride-induced decreases in blood pressure are greater in the standing than in the supine position, and orthostatic hypotension can occur. In general, it does not affect renal function in mild to severe hypertensive patients.
Pharmacokinetics: Distribution: Labetalol hydrochloride has been shown to cross the placental barrier in humans. Labetalol hydrochloride is approximately 50% protein bound. Neither hemodialysis nor peritoneal dialysis removes a significant amount of labetalol hydrochloride from the general circulation (<1% of a dose).
Metabolism and Excretion: Following intravenous infusion, the elimination half-life is about 5.5 hours and the total body clearance is approximately 33 mL/min/kg. In patients with decreased hepatic or renal function, the elimination half-life of labetalol hydrochloride is not altered. The metabolism of labetalol hydrochloride is mainly through conjugation to glucuronide metabolites. These metabolites are present in plasma and are excreted in the urine and, via the bile, into the feces. Approximately 55% to 66% of a dose appears in the urine as conjugates or unchanged labetalol hydrochloride within the first 24 hours of dosing.