Quiz 16: Adrenergic Antagonists


According to the given case, the patient (Mr. Perry) is allergic to cats, and he has been successfully treated for the hypertension, with the Propranolol. He recently visited his grandson, who has the kitten. As allergic to cats, the patient experienced the running nose and weepy eyes. The patient (Mr. Perry) is considering the OTC (over-the counter) Pseudoephedrine could relives his allergic symptom; but, it won't give the cure the allergic symptoms, rather than increases the blood pressure. Because, the drug Pseudoephedrine is an adrenergic agonist, which causes the vasoconstriction, and results in the increased blood pressure. In addition, the adrenergic agonist antagonizes the action of Propranolol, which results in the ineffective action of Propranolol. So, the increased blood pressure will be the result, when the patient taking the OTC- Pseudoephedrine.

The cholinergic agonists are similar to the acetylcholine and binds to the choline receptors for the parasympathetic effects. But, the adrenergic antagonists are competes with the norepinephrine for the adrenergic receptors, results in the activation of parasympathetic nervous system. Hence, the adrenergic antagonists, and the cholinergic agonists produces the similar physiological actions, but their indications for the pharmacotherapy are different. The primary indications for the usage of cholinergic agonists are listed below. • Urinary retention. • Open angle Glaucoma. • Myasthenia Gravis. • Sj gren's Syndrome. • Alzheimer's disease. • Gastric Atony (delayed emptying of stomach).

Prazosin: Prazosin is an antihypertensive class of drug, functions as a selective-alpha 1 adrenergic antagonist. As an antihypertensive role, the drug Prazosin, reduces the blood pressure by relaxing the blood vessels or reducing the peripheral resistance. Mechanism of action: The drug Prazosin relaxes the blood vessels, by competing with the Norepinephrine (NE) at alpha adrenergic receptors, on vascular smooth muscle in the arterioles and veins; which results in the reduction of peripheral resistance. So, the blood flows through the blood vessels by without any resistance, which results in the reduction in hypertension (blood pressure). Note: As said above, the drug Prazosin is a selective-alpha 1 adrenergic antagonist; hence, there is no action on the alpha 2 or beta adrenergic receptors.

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