Pharm Question, Would greatly appreciate any help

[MD12]

-I'm confused about the effect of low and high doses of epinephrine on bp as shown in FirstAid 2010. Could someone verify my following train of thought? Thanks so much in advance.

A low dose of epinephrine does NOT change bp?

B/c the stimulation of B1 increase in heart rate balances the B2 vasodilatation?

A high dose of epinephrine is more selective for a1, leading to an increase in bp?

When the a effects are blocked, a high dose of epinephrine will cause a drop in bp b/c at high doses, it is MORE selective for B2 than B1?

-Also, why does isoproterenol casue a DROP in bp? Shouldn't the B1 increase in heart rate balance the B2 vasodilatation leading to no change in bp just like low doses of epinephrine?

Something is wrong in my logic, I can feel it .

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[lemonade90]

-I'm confused about the effect of low and high doses of epinephrine on bp as shown in FirstAid 2010. Could someone verify my following train of thought? Thanks so much in advance.

A low dose of epinephrine does NOT change bp?

B/c the stimulation of B1 increase in heart rate balances the B2 vasodilatation?

A high dose of epinephrine is more selective for a1, leading to an increase in bp?

I don't really remember much about alpha and beta selectivity for epinephrine. Perhaps someone else could approach this.

-When the a effects are blocked, a high dose of epinephrine will cause a drop in bp b/c at high doses, it is MORE selective for B2 than B1?

-Also, why does isoproterenol casue a DROP in bp? Shouldn't the B1 increase in heart rate balance the B2 vasodilatation leading to no change in bp just like low doses of epinephrine?

Something is wrong in my logic, I can feel it .

Dr. Raymon at Kaplan seems to indicate that B2 effects overpower B1 effects when they compete. As a result, you will get drops in BP.

 

[Phloston]

Hey, I had posted a response to this on someone else's thread a couple weeks ago, based on a question I had encountered in Kaplan QBook:

http://forums.studentdoctor.net/showthread.php?t=919131

 

[Eilat87]

The way I made sense of it was that the effects of B2 is always stronger than that of B1.

 

[Aclamity]

-I'm confused about the effect of low and high doses of epinephrine on bp as shown in FirstAid 2010. Could someone verify my following train of thought? Thanks so much in advance.

A low dose of epinephrine does NOT change bp?

B/c the stimulation of B1 increase in heart rate balances the B2 vasodilatation?

A high dose of epinephrine is more selective for a1, leading to an increase in bp?

When the a effects are blocked, a high dose of epinephrine will cause a drop in bp b/c at high doses, it is MORE selective for B2 than B1?

-Also, why does isoproterenol casue a DROP in bp? Shouldn't the B1 increase in heart rate balance the B2 vasodilatation leading to no change in bp just like low doses of epinephrine?

Something is wrong in my logic, I can feel it .

As far as BP goes, it's mostly dependent on peripheral vascular resistance--inversely proportional to r^4 (that's why the b2 effects override the b1 effects on BP when you give isoproterenol). So if you're wondering what effect a drug has on BP, ALWAYS look at what it does to the vessels. If it doesn't do anything to vessels, then you can look at what it does to HR/CO and stuff.