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, Aldomet is the second most common antihypertensive drug used in pregnant women, whereas clonidine is definitively categorically not used in pregnancy. 02:04 So, these two drugs are very very different in one very important respect, is that Aldomet is used in pregnancy, clonidine is never used in pregnancy.
The lecture Alpha Agonists – Drugs in Hypertension by Pravin Shukle, MD is from the course Cardiovascular Pharmacology. It contains the following chapters:
Which antihypertensive drug is safe during pregnancy?
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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.