DrVirgo
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49. After taking an overdose of propranolol, a 35-year-old woman develops sinus bradycardia and syncope. In order to stimulate the same second messenger system that is activated by â-adrenergic receptors, which of the following drugs will be most effective to increase her heart rate?
A ) ADH (vasopressin)
B ) Atrial natriuretic peptide
C ) Clonidine
D ) Glucagon
E ) Phenylephrine
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| doc179
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is it D?
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| lalitha
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the ans is D
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| DrVirgo
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Are you sure?
Glucagon activates Gs and Alpha 1 activates Gq.
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| robin082006
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E?
ADH: V1, V2. indicated for ADH deficiency, Gq
ANP: systemic vasodilation, maybe due to decrease the release of sympathetic products
Clonidine: Alpha2 agonist, used in hypertension, Gi
Glucagon: used in beta blocker intoxication, Gs
phenylephrine: alpha 1 agonist, Gq, used as decongestant and mydriasis without cycloplegia
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| doc179
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I had not understood the question...I think they want us to choose drug to reverse bradycardia by using the same second messenger system as A-adrenergics..If what I have understood now is correct then the ans is E ( phenylephrine)..and if we are asked to use that second messenger system that is used by B-adrenergics then the ans is glucagon
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| robin082006
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I'm confused too because phenylephrine is not used for such purposes
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| DrVirgo
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Sorry all, I think there may be a typo in the question:
I think it should say:
49. After taking an overdose of propranolol, a 35-year-old woman develops sinus bradycardia and syncope. In order to stimulate the same second messenger system that is activated by BETA-adrenergic receptors, which of the following drugs will be most effective to increase her heart rate?
A ) ADH (vasopressin)
B ) Atrial natriuretic peptide
C ) Clonidine
D ) Glucagon
E ) Phenylephrine
Then people who said D) Glucagon are right...
Well, alpha receptors are not involved in increase heart rate (alpha 1 is responsible for increasing diastolic pressure and thereby increasing TPR; alpha 2 is to decrease blood pressure and is used in hypertension)
Beta 1 is the only one that increases HR… A stimulation of Beta 1 receptors activates a G protein (Gs). Glucagon also has a similar action by activating the same G protein Gs.
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| Nan
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Anecdotal evidence suggests a benefit of higher doses of glucagon in the treatment of overdose with beta blockers; the likely mechanism of action is the increase of cAMP in the myocardium, effectively bypassing the inhibitory action of the β-adrenergic second messenger system
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