Labetalol is part of a class of drugs called beta-adrenergic blocking agents, or beta blockers for short. As the name implies, beta blockers block beta receptors in the body. Beta receptors are located in a number of places, including the heart and blood vessels. These receptors are what stress hormones such as adrenaline attach to and cause certain reactions in the body, such as an increase in:
By blocking beta receptors, labetalol causes the reverse effect of stress hormones. It decreases heart rate and both systolic and diastolic blood pressure, as well as the workload of the heart.
Unlike a lot of other beta blockers, this medication also blocks alpha receptors. The alpha blocker component works more on the peripheral blood vessels (arteries and veins in the arms and legs). By blocking the alpha receptors, labetalol causes these blood vessels to relax.
Effects of Labetalol
A blood pressure reading consists of two numbers -- for example, 120/80. The top number is the systolic blood pressure, and the bottom number is the diastolic blood pressure. During clinical studies in people taking labetalol, both systolic and diastolic blood pressure decreased significantly. The higher the dose, the greater the drop in blood pressure tended to be.
Food and Drug Administration, Center for Drug Evaluation and Research. Electronic orange book: Approved drug products with therapeutic equivalence evaluations. FDA Web site. Available at: http://www.fda.gov/cder/ob/.
Briggs GG, Freeman RK, Yaffe SJ. Drugs in Pregnancy and Lactation. 8th ed. Philadelphia (PA): Lippincott Williams & Wilkins;2008.
National Library of Medicine (US). Drugs and Lactation Database (LactMED). NLM Web site. Available at: http://toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen?LACT. Accessed April 23, 2009.
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