Pharm Q - lovetest

[ArchivalUser]

Hi psycho. I haven't seen you in a while I hope you are well.
The correct answer is EE. Maryam put it nicely.
Good luck to everyone,
L.

[ArchivalUser]

First of al isoprotenrol is a beta agonist with B1 =B2 ,so the blocker in order to block HAS TO WORK on the SAME RECEPTORS…
Propranolol is the one who an do that jobs nicely and NE has only Alfa1 and Alfa 2 and b1 ,so no effect on B2,so it is very easy to immediately look for the answer E….Propranolol..
EE

[ArchivalUser]

plz can someone explain me:
if we block B1 how can NE affect the HR through alpha 1 and 2,
alpha 1 acts on the periphery, it has no Rp in the heart!!

[ArchivalUser]

@laurier

NE acting on alpha-1(vessels)----------->Reflex Bradycardia(Dec HR) (M-receptor)

[ArchivalUser]

ok I see know,
the q didn't specify if NE induce brady or tachy, i was thinking tachy.

thank you sarim

[ArchivalUser]

Beta 1 receptor =Increase HR,so when we THINK about HR we think of B1 receptors who INCREASE the HR. Now Isoproterenol is acting on the B1 and B2 equally and bc of the B1 receptor activation will lead to Increase HR. Than propranolol will block the effect on both B1 and B2 receptors ,but by the blocking the effect on B2 –propranolol will DECREASE the HR.
Now propranolol can’t do this with NE bc NE is activating Alfa 1 and 2 and Beta 1 and has no effect on Beta 2 receptors. Therefore propranolol can’t block a B2 in NE when it is Not in there..
Why we are making things complicated…
HR is always with B1 receptors and at ANY TIME when we INCREASE THE HR ,we will have drop on diastolic pressure 9aftherload ) which is associated with Alfa 1 receptors.
In this question we need to understand the B receptors function and if we know what isoprotenolol is and that ISO is acting on B1 and B2, than we have to know that the blocker has to work on the same receptors in order to block. It took me a lot of time to understand this.
Cio
Antonella

[ArchivalUser]

Hello Antonella. You are absolutely right

A Q for you.

When u give NE, what is the response on the HR ?

[ArchivalUser]

Ok,let me clear the thing again-propranolol is blocking both beta 1 and B 2 and yes NE - besides the effect on Alfa 1 and 2 ,has ONLY B1 ,but not B2,so it is logical that propranolol has to block B1 and decrease the HR,BUT why that doesn’t HAPPEN??
If NE act on B1 that means NE will INCREASE the HR and increase the pulse pressure that will lead to increase systolic pressure. and that is why in HYPOTENSION we give NE.
Again WHY propranol is not decreasing the HR in NE since act on the same B 1 receptors???

The above question can be answer it w/o even thinking about NE bc the ONLY one that acts on the same receptors as ISOPROTE...is PROPRANOLOL..
Antonella

[ArchivalUser]

Thank u

Here is my understanding:

In the stem they used the word "Intact subject" ----->

-Here it means that if given drugs have any effect on peripheral blood vessels(constriction or dilation), it will exert a "Reflex response on Heart'

NOTE: * we know that "Reflex response is predominant over Direct response"

Isoproterenol:

B2 (vassodilate)------>Reflex Inc HR (via Beta 1)
B1 ----------------------------->Inc HR (Direct effect)

-in above direct effect and Reflex effect are same via B1 receptor
-Propronolol will cancel it out


NE:

Alpha-1 (vasoconstriction)------>*Reflex Decr HR (via M receptors)
B1------------------------------------------>Incre HR (Direct effect *** but is hidden)

-Direct effect is hidden cause of the "Predominant Reflexive Heart response (Decr HR)

-Now when we give this pt Propronolol, it will act on blocking the B1 receptors on heart----But we don't see any change in heart response as the B1 response is already suppressed (due to predominant Reflex response).......and that is why propronolol dose not block heart response in this case.

[ArchivalUser]

Yes, we can frame the thinking also this way-if the propranolol blocks the Beta1, but the Alfa 1 and Alfa 2 is in there. Alfa 1 will INCREASE TPR and that will lead to reflex bradycardia due to increase M2 that are in the AV and SA node. This is like the vicious cycle.
Thanks Sarim.Please post something challenging, but yet important concept.
Cio
Antonella
Now ,we are all set to "kill " the adrenergic pharm a ??