gr_calif
Forum Junior
Topics: 3
Posts: 51
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IV administration of drug X to an anesthetized animal produces an
increase in blood pressure. After administration of drug Y,
readministration of drug X produces a decrease in blood pressure.
Which of the following pairs of drugs could produce this sequence of events?
Drug X -Drug Y
A. Acetylcholine - Neostigmine
B. Epinephrine - Phentolamine
C. Isoproterenol - Atropine
D. Norepinephrine - Propranolol
E. Phenylephrine - Hexamethonium
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| usmleasr
Forum Guru
Topics: 105
Posts: 970
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B...epinephrine and phentolamine.... 8)
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| gr_calif
Forum Junior
Topics: 3
Posts: 51
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COOL...U R ABSOLUTELY RIGHT! 
Epinephrine is an agonist at alpha-1, alpha-2, beta-1, and beta-2 receptors; phentolamine is an antagonist at alpha-1 and alpha-2 receptors. Therefore, after the administration of phentolamine, epinephrine can stimulate only beta receptors, which would produce a decrease in BP. Epinephrine is now acting like isoproterenol. This is called epinephrine reversal (the name stems from the fact that epinephrine originally increases BP and then produces the opposite effect after phentolamine administration). Therefore, choice B is the correct answer.
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| Aishvarya
Forum Newbie
Topics: 4
Posts: 32
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What would be the change in response of phenylephrine on blood pressure after phentolamine inj.??
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| ksc
Forum Newbie
Topics: 1
Posts: 11
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I think There would be a decrease in BP because the alpha response is blocked by the phentolamine which is a alpha 1 receptor blocker. Which would cause a decrease in tpr because the vasoconstriction effect of the alpha drug would be blocked. :icon_scratch:
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| Aishvarya
Forum Newbie
Topics: 4
Posts: 32
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suppression of pressor effect,TO NORMAL LEVEL OF BP,NOT BELOW NORMAL
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| ksc
Forum Newbie
Topics: 1
Posts: 11
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Thank's that was what I was trying to figure out but I have been getting so confused with reflexes lately I feel Like I don't know which way is up.
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