Pharmacology: Pharmacodynamics: Labetalol lowers blood pressure by blocking peripheral arteriolar α-adrenoceptors, thus reducing peripheral resistance, and by concurrent β-blockade, protects the heart from reflex sympathetic drive that would otherwise occur. Cardiac output is not significantly reduced at rest or after moderate exercise. Increases in systolic blood pressure during exercise are reduced but corresponding changes in diastolic pressure are essentially normal. All these effects would be expected to benefit hypertensive patients.
Labetalol does not adversely affect renal function and is particularly suitable for use in hypertensive patients with renal disease.
Pharmacokinetics: The plasma half-life of Labetalol is about four hours. About 50% of Labetalol in the blood is protein bound. Labetalol is metabolised mainly through conjugation to inactive glucuronide metabolites. These are excreted both in the urine and via the bile, into the faeces. Only negligible amounts of Labetalol cross the blood brain barrier in animal studies. Labetalol crosses the placental barrier and secreted in breast milk.