Alpha Agonists – Drugs in Hypertension

by Pravin Shukle, MD

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    00:01 Let's move on to those drugs that act on the sympathetic nervous system, specifically we are just going to focus on alpha agonists right now.

    00:10 So, these alpha agonists are often very good drugs. There we have the alpha 1 agonists like phenylepherine, and alpha 2 agonists like alpha-methyldopa and clonidine.

    00:22 Now, phenylepherine is an alpha 1 agonist and that will actually cause constriction of the blood vessel and it causes high blood pressure. So, we put it there just to remind you that alpha 1 and alpha 2 have very different effects. Obviously, we don't use phenylepherine to treat hypertension because it causes high blood pressure.

    00:42 Let's go on to the alpha 2 agonists. So, alpha-methyldopa and clonidine.

    00:49 Let's compare and contrast alpha-methyldopa and clonidine.

    00:53 The alpha-methyldopa or I'm going to call it Aldomet for simplicity sake, decreases central sympathetic outflow.

    01:00 Similarly, clonidine does the same thing.

    01:04 Aldomet is a prodrug. It is metabolized to the active agent.

    01:11 Both will decrease central sympathetic outflow, cardiac output, and vascular resistance.

    01:20 Both have a compensatory reaction of salt retention. They both do this.

    01:27 There are some idiosyncratic reactions which distinguish the two drugs.

    01:31 The idiosyncratic reaction of note with Aldomet is hemolytic anemia.

    01:36 The idiosyncratic reaction of clonidine is rebound hypertension.

    01:42 Both of course cause sedation cause they're working centrally.

    01:47 In terms of use, Aldomet was previously used extensively in pregnant patients.

    01:52 In fact, it is still a viable antihypertensive choice for pregnant women, whereas clonidine is not typically used in pregnancy.

    About the Lecture

    The lecture Alpha Agonists – Drugs in Hypertension by Pravin Shukle, MD is from the course Cardiovascular Pharmacology. It contains the following chapters:

    • α-Agonists
    • α-Methyldopa and Clonidine

    Included Quiz Questions

    1. Methyldopa (Aldomet)
    2. Clonidine
    3. Angiotensin-converting enzyme inhibitors
    4. Hydrochlorothiazide
    5. Diuretics

    Author of lecture Alpha Agonists – Drugs in Hypertension

     Pravin Shukle, MD

    Pravin Shukle, MD

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    By Robert R. on 03. April 2020 for Alpha Agonists – Drugs in Hypertension

    Very pleasant pace of lecture and clear explanation. Also love the quick and personal response on the questions on the forum. Really makes me feel like I am in the lecture hall itself.