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  #1  
Old 02-19-2011
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Drug How to answer Autonomic Pharmacology Questions

Can anyone please explain me easy way to remember cholinergic/adrenergic agonists/antagonists actions (especially on BP, HR, pulse pressure, TPR). I have read them over and over again and still choose the wrong answer in questions like this below:


S is
  1. Epinephrine
  2. Norepinephrine
  3. Phenylephrine
  4. Isoproterenol
  5. Albuterol.
How to answer Autonomic Pharmacology Questions-dr.jpg
click image to enlarge
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  #2  
Old 02-19-2011
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Let me tell u a secret mantra!

Watch Dr. Raymond's lectures in kaplan videos and then read notes at least twice.

After that practice 100 autonomic Qs in the attached file; exactly 100, not one more or one less. if u do one more or one less Q, u will lose all your knowledge.

Even after that u don't understand, then, God help u Child!
Attached Files
File Type: pdf Autonomic_Pharm.pdf (225.2 KB)
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Old 02-19-2011
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Quote:
Originally Posted by drahmednawaz View Post
Let me tell u a secret mantra!

Watch Dr. Raymond's lectures in kaplan videos and then read notes at least twice.

After that practice 100 autonomic Qs in the attached file; exactly 100, not one more or one less. if u do one more or one less Q, u will lose all your knowledge.

Even after that u don't understand, then, God help u Child!
You make it sound like some magic spell.
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  #4  
Old 02-19-2011
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Quote:
Originally Posted by mle2resident View Post
Can anyone please explain me easy way to remember cholinergic/adrenergic agonists/antagonists actions(especially on BP, HR, pulse pressure, TPR). I have read them over and over again and still choose the wrong answer in questions like this below:


S is
  1. Epinephrine
  2. Norepinephrine
  3. Phenylephrine
  4. Isoproterenol
  5. Albuterol.
Ill take a stab at the question:

First you recognize what each of the drugs listen acts on:

Epinephrine: a1, a2, b1, b2
Norepinephrine: a1, a2, b1 (a2 is negligible)
Phenylephrine: a1 (agonist)
Isoproterenol: Same actions of low dose Epi so: a1, a2, b1, b2
Albuterol: B2 blocker

ABCD (A-Constricts, B-Dialates)

Correction: It is Epinephrine.

Reason: All you have to do is look at actions of Propranolol (beta2 blocker) and Phenoxybensamine (alpha antagonist).

With administration of Epi, on Propranol, B2 blocker actions vs. B2 agonist actions of Epi are abolished (cancels out) so left is action of A1, meaning VC and Increase TPR, so there is increased BP.

Action on Phenoxybenzamine, Alpha Antagonist. Administration of Epi, (a1, b1, b2), cancels actions of A1 agonist, so all that is left is B1, B2, which leads to a decrease in the BP.

So, it would be Epi.

The reasons why: it is not NE (A1, B1 actions only), albuterol (B2 Agonist), Phenylephirine (A Agonist), Isoproternol (Low dose action of Epi)


Im not 100% though.
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  #5  
Old 02-19-2011
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Answer is Epinephrine.

To attack at Qs like this, see what kind of receptors r invovled. S causes increase in BP, HR and pulse pressure. a1 and b1 and b2 receptors involved.

let us confirm that.

a1 blockade (phenox) reverses (first increased, now lowered) blood pressure. Q is solved at this point. There is only one drug where a1 bockade reverses blood pressure. Epinephrine.
ganglionic blockade (mecamyl) has no effect. no reflexes involved. effects come from pure reeptors.
B1 and B2 Blockade (proprano) abolishes HR and Pulse Pressure changes, now only a1 effects.
a1, b1 and b2 receptors confirmed. it is epinephrine. b2 receptors r not inerveted; so no norepinephrine effects.

This is one of the classic Qs, because it has a BIG CLASSIC clinical use. Every student should and must know this.

Classic clinic use is that in shock u r giving epi. Actually we titrate drugs like epi. if we give too much, there is so much vasoconstriction that limb ischemia and gangrene occurs. this is where u should immediately give a1 blockers.

Surely it is not phenyephrine. with pheny, HR changes would be due to reflexes and mecamyl would abolish them; and a1 blockade would abolish all phenyl effects. here with a1 blockade we still see lowered BP (b2 effect) and increased HR (b1 effect).

If u want to master autonomics, watch Dr. Raymond's lectures in kap videos.
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Old 02-19-2011
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Quote:
Originally Posted by drahmednawaz View Post
Answer is Epinephrine.

To attack at Qs like this, see what kind of receptors r invovled. S causes increase in BP, HR and pulse pressure. a1 and b1 and b2 receptors involved.

let us confirm that.

a1 blockade (phenox) reverses (first increased, now lowered) blood pressure. Q is solved at this point. There is only one drug where a1 bockade reverses blood pressure. Epinephrine.
ganglionic blockade (mecamyl) has no effect. no reflexes involved. effects come from pure reeptors.
B1 and B2 Blockade (proprano) abolishes HR and Pulse Pressure changes, now only a1 effects.
a1, b1 and b2 receptors confirmed. it is epinephrine. b2 receptors r not inerveted; so no norepinephrine effects.

This is one of the classic Qs, because it has a BIG CLASSIC clinical use. Every student should and must know this.

Classic clinic use is that in shock u r giving epi. Actually we titrate drugs like epi. if we give too much, there is so much vasoconstriction that limb ischemia and gangrene occurs. this is where u should immediately give a1 blockers.

Surely it is not phenyephrine. with pheny, HR changes would be due to reflexes and mecamyl would abolish them; and a1 blockade would abolish all phenyl effects. here with a1 blockade we still see lowered BP (b2 effect) and increased HR (b1 effect).

If u want to master autonomics, watch Dr. Raymond's lectures in kap videos.
How did you determine increased HR? The diagram provided, its barely visible.

But yes, you are correct to state that it is infact Epinephrine.

Can you explain reason behind why it can't be Isoproternol? because I remember Dr. Raymon saying that it has same actions as low dose epi. So wouldn't that be a possibility?
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You have to look at just not the figure; other clues as well. They is only one example where a1 blockade reverses BP: Epinephrine; and Epi has b1 effects. Propranolol is a non-selective (b1 and b2) blocker. b1 receptors r definitely involved.

it is not low-dose epi or isop, because BP reversal by a1 blockade occurs only with high-dose epi.
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Quote:
Originally Posted by drahmednawaz View Post
You have to look at just not the figure; other clues as well. They is only one example where a1 blockade reverses BP: Epinephrine; and Epi has b1 effects. Propranolol is a non-selective (b1 and b2) blocker. b1 receptors r definitely involved.
But B1 is only on the heart, and you are not able to see the HR on this diagram (its the diagram quality I know)
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Other clues, clues!! B1 and B2 bockade leaves only a1 effects and BP reversal.

In real exam, u can solve many, not all, multimedia Qs without the help of multimedia. look at the other clues.

Some pics r classic, u can solve those Qs by just looking at pics. This one is also classic.

it is not low-dose epi or isop, because BP reversal by a1 blockade occurs only with high-dose epi.
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Thank u PatelMD and drahmednawaz for ur valuable input. I got a clear idea how to approach such questions now.
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Default hello , where is the videos and lectures?

hello , where is the videos and lectures?

Quote:
Originally Posted by drahmednawaz View Post
Let me tell u a secret mantra!

Watch Dr. Raymond's lectures in kaplan videos and then read notes at least twice.

After that practice 100 autonomic Qs in the attached file; exactly 100, not one more or one less. if u do one more or one less Q, u will lose all your knowledge.

Even after that u don't understand, then, God help u Child!
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