A patient with hypertension is being treated with clonidine 0.1 mg PO twice a day. The nurse understands that this medication is lipid-soluble so it can cause vasodilation by acting on:

alpha-2 receptors in the brain.


• Clonidine is a central alpha-2 agonist. Since the medication is lipid soluble, it has the ability to cross the blood-brain barrier and reach the alpha-2 receptors in the brain. This reduces sympathetic outflow and slows heart rate and dilates blood vessels. 

• Alpha-1 receptors are found in vascular smooth muscle. Stimulation results in vasoconstriction (phenylephrine, norepinephrine) and inhibition results in vasodilation (carvedilol, labetalol - also block beta-1 receptors). 

• Beta-1 receptors are found in the heart. Stimulation results in increased contractility and heart rate (norepinephrine, dobutamine) and inhibition results in decreased heart rate and cardiac output (metoprolol, atenolol).

• Beta-2 receptors are found in smooth muscle such as the bronchi, coronary arteries, and skeletal muscle arteries. Stimulation results in smooth muscle relaxation (albuterol) and inhibition results in constriction (propranolol - also blocks beta-2 receptors).

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