nbme 5 3;10 - samomcos

[ArchivalUser]

BP/HR graphs...

C. NE and Prazosin, right?

[ArchivalUser]

DDD

drug Y (----) just increase the HR (either by blocking M receptors or stimulating beta-1)

prazosine and phentolamine can not be the choice cz both antagonize alpha-receptors and there no alpha-receptors on heart.
propranolol and metoprolol both block beta-1 which cz decrease in HR ,so can not be the choice.
drug Y is Atropin

drug X(_____) phenylephrine (alpha-1 agonist) vasoconstricted --->increase B.P.----->Reflex bradycardia

[ArchivalUser]

(- - - - ) is X and Y.

[ArchivalUser]

sarim when u r giving a drug it is increasing blood pressure and decresing heart rate it means the drugs main action is on the vessels and the bradycardia is reflex this is probably a drug with a potent alpha 1 action either it is BCD now
when u pretreat BP gets normal and Heart Rate increase that means it blocked the peripheral action of the drug and allowed the next best action i.e. increasing heart rate and normalised BP
Epi a1 a2 b1 b2 - phentolamine a1& a2 block - so Increase HR and decrese BP(b2 action) so option B ruled out
Now C and D
Phenylepi a1 only - atropine M block - Muscuranic receptors on the blood vessels perform vasodilation so if they are blocked they will constrict more plus it wud cause more increase BP and definetly increased HR - Cant be the outcome we see shud be Inc BP and Inc HR ans is definetly CCC
Norepi a1 a2 b1 - prazosin a1block so prominent b1 - increase HR and normal BP likely ans

Hope thats helps sarim bye

[ArchivalUser]

thanx for ur input arrythmia.my approach to second graph was wrong.i was taking it as TPR rather than Mean BP but still i think answer is DDD

now i'm confused.Lets try this.

1-aren't choice B and C the same thing(Epinephrine effect on alpha-1 or beta-2 are dose-dependent,so how would we know that it increases or decreases BP)

2-Drug Y we gave first(pretreatment as it says in the stem),so according to choice C if the drug X is NE then HR should go up???

3-i think mucuranic blockers DO NOT cz vasoconstriction.Its not like that vascular tone is under the controll of muscuranics.its just when we activate it ,it causes vasodilation---so blocking it will have Zero efficacy(direct effect).Now there could be a reflex vasodilatory effect cz of hyperthermia.So if we give ATROPIN it would have increased HR and reflex vasodilation(decrease TPR) so BP should be normalized with Tachycardia???-----and now when we give Phenylephrine(a-1 agonist), it cz vasoconstriction(increase TPR)--->increase in BP and would lead to reflex bradycardia?????

please help me on this one....

[ArchivalUser]

they are talking abt the effect of drugs after and before pretreatment dude hope that helps

[ArchivalUser]

Only on X (NE): [alpha1 > beta1] : causes vasoconstriction and reflex decrease in heart rate.

PreRx with Y(Prazosin), then X: [blocks the alpha1 effect]: no more vasoconstriction & BP remains at baseline, unopposed beta1 effect--> tachycardia.

[ArchivalUser]

arrythmia & sam thanx alot.Agreeeeeee it is CCC

i always have thought that if ur approach to a Q is in opposite(wrong) direction it is less likely that u'll come back to think right within one minute time and it took me hours to get this one.

[ArchivalUser]

anyone plz help me download the NBME q bank for free, thank you