Effect of medium dose epinephrine - USMLE Forums
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Old 03-22-2012
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Drug Effect of medium dose epinephrine

Can somebody explain me the effect of med dose epi???as shown by a graphical pic in kaplan...i just never cud understand it..thanks
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Old 03-22-2012
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Basically, with medium dose epinephrine you have a dominant effect at Beta 1 receptors and an equal effect at Beta 2 and Alpha 1 receptors.

Beta 1 = Increases HR, Increases Pulse pressure (the difference between systolic & diastolic)

Beta 2 = Decreases TPR
Alpha 1 = Increases TPR
Therefore, there is no change in TPR and the Mean Arterial Pressure stays the same!


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Old 03-22-2012
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lol I hope my paint skills were sufficient!
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Originally Posted by Hope2Pass View Post
Basically, with medium dose epinephrine you have a dominant effect at Beta 1 receptors and an equal effect at Beta 2 and Alpha 1 receptors.

Beta 1 = Increases HR, Increases Pulse pressure (the difference between systolic & diastolic)

Beta 2 = Decreases TPR
Alpha 1 = Increases TPR
Therefore, there is no change in TPR and the Mean Arterial Pressure stays the same!


Sorry to ask this dumb Q but... If I got it okay, then the beta-2 and alpha-1 effect will block each other... right?
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Sorry to ask this dumb Q but... If I got it okay, then the beta-2 and alpha-1 effect will block each other... right?
No question is dumb! And yes they counteract and oppose each others actions and that's why there is no change in TPR or MAP.

Also, whenever there is a change in TPR it will ALWAYS have a reflex on Heart Rate. But when there is a change in HR it will NEVER have a reflex on TPR. (just a fyi, although I'm sure you knew that!)
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Old 03-22-2012
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Quote:
Originally Posted by Dr. Mexito View Post
Sorry to ask this dumb Q but... If I got it okay, then the beta-2 and alpha-1 effect will block each other... right?


ur question isnt dumb!!! u have to know this by heart.. coz there were two pharma question i came across in kaplan qbank,
where the idea of the question was to see if u knew this fact or not [they said that they administered an alpha blocker [i.e phentolamin] and then after that they gave the guy epinephrine..... what would be the result?? --> decreased TPR

yes, even after giving EN.... and thats coz the alpha is blocked, and the beta-2 is left unopposed to work.. u'll get vasodilatation and then decreased TPR


nothing is dumb in step1!!!
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Old 03-22-2012
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Default Thanks a lot....

Thanks for the explainataion
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