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45 Cards in this Set
- Front
- Back
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Nodal Agents – “Rate Control”
ABCD |
Adenosine
Beta Blockers (class II) Ca++ Channel Blockers (class IV) Digoxin |
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adenosine
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Acetylcholine/adenosine effect
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adenosine MOA in the heart
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Activates IKAch channels via Gβγ ⇨ hyperpolarizing force slows down AV nodal rate
↓ cAMP via Ga → decreased DAD’s, EAD’s |
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Where is the A1 receptor found in the heart?
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SA/AV Nodal Cells >> Cardiocytes
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what is an adenosine antagonist found in many beverages?
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caffeine
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adenosine pharmacology
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Extensive first pass metabolism
Re-uptake blocked by Dipyridamole Methylxanthines block A1 receptor |
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adenosine S/E
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Chest Discomfort, Bronchospasm
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Beta 1 Selectivity
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Metoprolol, Atenolol and Esmolol >>>>
Propranolol, Nadolol and Carvedilol |
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adverse effects and toxicity of Ca++ blockers
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Dizziness, headache, flushing, hypotension, edema, constipation, GERD, CHF, bradycardia and heart block (greater with verapamil)
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lipid soluble beta blockers
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Propranolol and Metoprolol
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water soluble beta blockers
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Nadolol, Atenolol, Esmolol
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metoprolol metabolism
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CYP2D6
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propranolol metabolism
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high first pass metabolism
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Which β blockers would you ↓dose in renal dysfunction?
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Atenolol and Nadolol
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mechanism of Ca++ channel blockers
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block voltage-gated “L-type” Ca++ channels --> ↓iCa++ in cardiac and vascular smooth muscle --> ↓HR and contractility and relax blood vessels
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Which β blockers would you ↓dose in liver dysfunction?
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Metoprolol and Propranolol
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Dihydropyridines
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Nifedipine
Amlodipine |
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non-Dihydropyridines
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Diltiazem
Verapamil |
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digoxin MOA
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Digoxin ┤Na+/K+ ATPase → ↑intracellular Na+ → ↑ Na+/Ca++ pump → ↑ intracellular Ca++
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digoxin and contractility
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↑Ca++ → +inotropic action
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digoxin and HR
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digoxin ↑vagal impulses and ↓sinus rate
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How does digoxin act on atria at toxic levels?
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increases sympathetic tone and Ca2+ loading leading to increased automaticity and DAD’s (delayed afterdepolarizations)
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Why would you avoid digoxin in Wolf-Parkinson White syndrome?
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It may improve conduction in some accessory pathways
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What does P-glycoprotein have to do with digoxin?
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It excretes absorbed digoxin back into gut lumen (also controls renal elimination)
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Quinidine + digoxin =
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Increases digoxin levels by displacing from binding sites and inhibiting P-glycoprotein system
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Amiodarone, Propafenone, or Verapamil + digoxin =
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decreases digoxin renal and non-renal clearance
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cyclosporine, anti-fungals, benzodiazepines + digoxin =
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inhibit P-glycoprotein so ↑digoxin
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non cardiac symptoms with digoxin toxicity
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anorexia, nausea, vomiting, changes in color vision including scotoma, halo vision and altered color perception
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cardiac digoxin toxicity
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Delayed afterdepolarizations (DADs)
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Bidirectional Ventricular tachycardia (think digoxin toxicity → Ca++ overload)
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What are some drugs that cause INCREASED Digoxin?
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Amiodarone
Cyclosporin Erythromycin Quinidine Tetracycline Verapamil |
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What drugs cause DECREASED Digoxin?
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Cholestyramine
Neomycin Rifampin |
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Why do you have to push adenosine so quickly?
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T1/2 < 10 sec
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Adenosine + Verapamil
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⇧risk of VF (Ventricular fibrillation)
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adenosine + theophylline≈(caffeine)
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decreased efficacy
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Why would a patient on metoprolol or propranolol get depressed?
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they are lipid soluble beta blockers
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β blockers % protein bound
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Esmolol (55%) > Nadolol (30%) > Metoprolol/Atenolol (10%)
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Why does % protein bound matter in pharmacology?
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if ↓liver function then ↓albumin
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Elimination Half Life for beta blockers
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Nadolol (20 hours) >>> Atenolol (6-7 hours)/Metoprolol (3-7 hours)/Propranolol (4 hours) >>> Esmolol (10 min)
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Only true once a day β blocker?
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Nadolol
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Which β blockers are renally excreted?
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Atenolol and Nadolol
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Which Ca++ channel blockers are used for HR control?
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Diltiazem
Verapamil |
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Verapamil metabolism
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CYP3A4
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Antidote for digoxin?
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Digoxin Immune Fab (Digibind®)
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