2023 MARCH SUMMATIVE

1.     Neostigmine:

 

• A.   Acts on acetylcholinesterases to block the action of Acetylcholine

• B.    Acts only on nicotinic receptors found on the parasympathetic postganglionic neurons

• C.    An anticholinesterase which amplifies the action of Acetylcholine

• D.   Used in the treatment of Central Anticholinergic Syndrome

1.     Atropine:

D.  

• A.   Mimics the action of Acetylcholine at parasympathetic muscarinic receptors

• B.    Does not cross the blood brain barrier

• C.    Used in treatment of cholinergic crisis in patients with Myasthenia Gravis undergoing surgery

• A nicotinic agonist

1.     α1 adrenergic receptor:

• A.    Couple to Gq which increases cytosolic Ca++ and causes vasoconstriction

• B.    Agonists activates baroreceptor reflex tachycardia

• C.     Purely acted on by Ephedrine

• The predominantPredominant receptor acted on with lower doses of Epinephrine (<0.02mcg/kg/min

1.     ß2 adrenergic receptor

• A.   Coupled to Gq which results in increase in cytosolic Ca++ causing vasoconstriction

• B.    Primary mechanism is positive chronotropic and inotropic effects

• C.    Predominant receptor where norepinephrine acts

• D.   Stimulates formation of cAMP resulting in augment Ca++ uptake by SR resulting in vasodilation

1.     Dopamine receptors:

 

• A.   Agonists result in increased arterial pressure

• B.    Dopamine 2 receptors particularly dilate arterial vessels and increase renal, mesenteric and splenic blood flow

• C.    Stimulated by synthetic catecholamines

• D.   Stimulated by high doses of Dopamine(>10mcg/kg/min) but increased systemic vascular resistance as predominant clinical effect

1.     Epinephrine

• A.    At <0.02mcg/kg/min (lower doses), has receptor activity ß2> α1, ß1 hence summative effect is decreased SVR

• B.    At >0.1 mcg/kg/min (higher doses), has receptor activity ß2> α1, ß1 hence summative effect is increased SVR

• C.     At <0.02mcg/kg/min (lower doses), has receptor activity α1, ß1> ß2  hence summative effect is increased SVR

• D.    At >0.1 mcg/kg/min (higher doses), has receptor activity α1, ß1> ß2  hence summative effect is decreased SVR

1.     Norepinephrine

• A.   Causes pronounced tachycardia

• B.    Has receptor activity α1 = ß1 = ß2  

• C.    Different with epinephrine in its ß2 activity, with norepinephrine resulting in a more pronounced increase in SVR

• D.   Displaced by phenylephrine in the presynaptic postganglionic nerve terminals

1.     Ephedrine

• A.   Predominant effect is through endocytosis in ß2 presynaptic nerve terminals

• B.    Endocytosis displaces dopamine

• C.    Has indirect effect on α1 and ß1 adrenergic receptors

• D.   Has no tachyphylaxis

1.     B blockers

• A.   Esmolol is an example of a relatively selective ß1 blocker with a half life longer than Labetalol

• B.    Safe to use in poorly controlled DM

• C.    Propranolol is a selective ß blocker

• D.   Lowers risk of MI in patients with CAD by improving O2 supply as it increases diastolic time

1.     Diltiazem

• A.   Acts on voltage dependent T(transient) type calcium channels

• B.    Is a benxothiazepine that acts on myocardial>>vascular smooth muscles

• C.    Has more pronounced reflex tachycardia due to minimal negative inotropic, chronotropic effects

• D.   Is the only FDA approved medication for cerebral vasospasm