Antidysrhythmic Drug Part II Flashcards
What drug class does Amiodarone belong?
(Class III)
What is the characteristics of Amiodarone (Class III)?
Potent antiarrhythmic with wide spectrum of activity against refractory supraventricular and ventricular tachyarrhythmias
What is Amiodarone (Class III) effective in treating?
- Effective in tx WPW, decreases risk of Afib after cardiac surgery
- Tx of VT/VF resistant to defibrillation (in ACLS protocol)
What can Amiodarone (Class III) decrease?
Decreases mortality after MI
What is the MOA of Amiodarone (Class III)?
- Prolongs the ERP in all cardiac tissue (SA & AV node, atrium, His-Purkinje system, ventricles & accessory bypass tracts [WPW])
- Antiadrenergic effects (noncompetitive alpha and beta receptor blockade)
- Antianginal (dilates coronary arteries/increases coronary blood flow)
What is the cause of pulmonary toxicity associated with Amiodarone (Class III)?
poss R/T production of free oxygen radicals in the lungs
What can pulmonary toxicity with Amiodarone (Class III) lead to?
Can lead to ARDS, pulmonary edema
What effect can High FiO2 have on pulmonary toxicity of Amiodarone (Class III)?
High FiO2 may accelerate free oxygen radical damage to lung tissue
What effect can lower FiO2 have from pulmonary toxicity of Amiodarone (Class III)?
Lower FiO2 to lowest level capable of maintaining adequate systemic oxygenation
What is the side effects of Amiodarone-induced pulmonary toxicity?
dyspnea, cough, pulmonary infiltrates on CXR, hypoxemia
What are the CV effects of Amiodarone (Class III)?
- Prolong QTc interval on ECG
- proarrhythmic effect (incr. risk of torsades)
- slow HR resistant to atropine
- decreased responsiveness to sympathomimetics since it blocks these receptors
How is hypotension occurs from Amiodarone (Class III)?
Hypotension d/t peripheral vasodilating effect: (tx w/vasopressin)
What can enhance the negative inotropic effects of Amiodarone (Class III)?
Negative inotropic effects enhanced w/admin of GA, β-blockers, CCBs
What are some other side effevts associated with Amiodarone (Class III)?
- Optic neuropathy
- photosensitivity
- rash
- cyanotic discoloration of face
- neurologic toxicity (peripheral neuropathy, tremors)
What is the half life of Amiodarone (Class III)?
Long elimination half-time (29 days)
What is the volume of Vd of Amiodarone (Class III)?
large Vd
What is the protein binding of Amiodarone (Class III)?
Extensive tissue protein binding
What is the active metabolite for Amiodarone (Class III)?
longer elim half-time than parent drug leads to accumulation of metabolite w/chronic therapy
What medications can effect Amiodarone (Class III) drug levels?
Inhibits P450 enzymes so can increase drug levels: digoxin, procainamide, quinidine, warfarin, cyclosporine, quinidine, procainamide, phenytoin
What is true about digoxin and Amiodarone (Class III)?
Displaces digoxin from protein binding sites (digoxin dose should be by 50%)
What does Amiodarone (Class III) contain?
Amiodarone contains iodine; has effects on thyroid function (hyper or hypothyroidism)
What are the drug classes of Sotalol?
(Class III)
What is the properties of Sotalol (Class III)?
Nonselective β-adrenergic antagonist at low doses, higher doses prolongs cardiac AP in atria, ventricles and accessory tracts
What effect can be seen with Sotalol (Class III)?
β blockade effects: decreased contractility, bradycardia, delayed AV
What is the clinical uses of Sotalol (Class III)?
Treatment of sustained VT/VF, a-tachycardia, & afib
When should Sotalol (Class III) be avoided?
Avoid in asthmatics, LV dysfunction, conduction abnormalities such as prolonged QTc interval on ECG
When is Sotalol (Class III) used?
Proarrhythmic; use saved for life threatening ventricular arrhythmias
What is the excretion of Sotalol (Class III)? When is this a concern?
Excreted by kidneys, concerns with renal dysfunction
What is the metabolism of Sotalol (Class III)?
not metabolized
What is the most serious effect of Sotalol (Class III)?
side effect is Torsades de pointes that is dose related (prolongs the QTc)
What are the drug class of Ibutilide/Dofetilide?
(Class III)
What is the use of Ibutilide?
recent onset of Afib/Aflutter
What is a property of Ibutilide?
Polymorphic VT with +/- QT prolongation that can be problematic with those with predisposing factors
What is the metabolism of Ibutilide?
Hepatic metabolism
What is MOA of Dofetilide?
potent, pure K+ channel blocker (prolongs cardiac AP duration)
What can Dofetilide prolong?
Prolongs QTc
When is Dofetilide used?
in tx of recent onset Afib/Aflutter to convert to NSR and for maintenance
What is the exertion of Dofetilide?
Mostly excreted unchanged in the urine (renal dysfunction concerns)
What is the properites of Dofetilide administered with CCB?
Proarrhythmic when coadministered with CCB’s
What is the FDA mandate with Dofetilide?
must be admitted for cardiac monitoring for at least 72 hrs during initiation of treatment due to determine presence of QT prolongation
What is the class of Verapamil?
Class IV
What is the clinical use of Verapamil?
Verapamil (phenylalkylamine CCB):Tx of paroxysmal SVT, control ventricular rate in Afib/Aflutter
What is the MOA of Verapamil?
Inhibits flux of calcium ions across the slow channels of vascular smooth muscle & cardiac cells
What effect of does Verapamil have on the cardiac AP?
- Decreases rate of Phase 4 spontaneous depolarization
What are the properties of Verapamil?
- Depresses AV node
- negative chronotropic effect on SA node
- negative inotropic effect
What can be seen in moderate degrees of Verapamil?
Moderate degree of coronary and systemic artery vasodilation
What causes the side effects with Verapamil?
Side effects due to effects on calcium ion flux into cardiac cells
What are the side effects of Verapamil?
- AV block, cardiac depressant (enhanced in LV dysfunction), hypotension, exaggerate effects of neuromuscular blocking drugs
What can occur when Verapamil is delivered with propranolol?
Careful with coadministration with propranolol (severe bradycardia)
What can increase Verapamil concentrations?
Cimetidine may increase verapamil plasma concentrations
What can increase digoxin doses?
Quinidine, verapamil, amiodarone may increase digoxin levels
What are the vasodilating effects of Verapamil?
Vasodilating effects (treat vasospastic angina and HTN), negative inotrope
What can Verapamil precipitate?
Can precipitate ventricular arrhythmias for patients with WPW syndrome
What is the drug class of Diltiazem?
A benzothiazepine CCB
What is the MOA of Diltiazem?
Along with L-type Ca++ channel, may also work on the Na+/K+ pump to decrease the intracellular Na+ exchanged for extracellular Ca++ and may inhibit the Ca++ /calmodulin binding
What can Diltiazem be used for?
Mainly blocks AV node, used with SVT’s, can be used to tx HTN
What are the myocardial effects of Diltiazem?
Minimal myocardial depressant effects and unlikely to interact with β blockers
What is the dose Diltiazem?
- IV dose 0.25-0.35 mg/kg over 2 minutes and repeated in 15 min.
- Infusion after bolus for 24 hrs (10mg/hr)
What is the elimination of Diltiazem? When is the prolonged?
- 4Elimination half time 4-6 hrs, 20 hrs with active metabolites (prolonged with liver disease)
What does Diltiazem control?
Commonly used to control HR
What are the properties of Diltiazem in comparison to Verapamil?
Unlike verapamil: minimal cardiac depressant and unlikely to interact with B-blockers
What effect does if have on the Na Channels?
Like verapamil: has local anesthetic properties (Na+) channels
What is MOA of Adenosine?
Endogenous nucleoside that slows conduction through AV node
What is the use for adenosine?
Used in tx of paroxysmal SVT (including accessory pathways with WPW)
When is Adenosine not effective?
Not effective for Vtach, Afib, Aflutter
What is the dose of Adenosine?
Usual dose is 6 mg rapid IV injection followed by 6-12 mg IV 3 minutes later
What is the elimination half time of Adenosine?
Elimination half life 10 sec
What are adenosine receptors are indicated in what?
Adenosine receptors indicated for treatment of pain
What are adenosine receptors?
Adenosine receptors comprise a group of G protein-coupled receptors which mediate the physiological actions of adenosine
How many adenosine receptors are there?
To date, four AR subtypes have identified in different tissues.
What is true about adenosine receptors?
These receptors have distinct localization, signal transduction pathways and different means of regulation upon exposure to agonists
What do adensoine1 receptors increase?
Adenosine1 receptors increase K+ currents, hyperpolarize the cell membrane, shorten AP
What does activation of G-protein Adenosine receptors cause?
Activation of the G-protein also decreases cAMP, which inhibits L-type calcium channels and therefore calcium entry into the cell
What effect do adenosine1 receptors have on the AP of cardiac cells?
In cardiac pacemaker cells located in the SA node, adenosine acting through adenosine1 receptors inhibits the pacemaker current which decreases the slope of phase 4 of the pacemaker AP
What are side effects of Adenosine?
With rapid IV injection: facial flushing, headache, dyspnea, chest discomfort and nausea
Patients who recieve Adenosine often have a felling of _________
impending doom
What can Adenosine produce?
May produce transient AV block
Who should Adenosine be used cautiously in?
Bronchospasm for those predisposed (caution with active wheezing)
What antagonizes Adenosine?
Antagonized by methylxanthines such as theophylline and caffeine
What does this EKG strip show?
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Adenosine “pause” on ECG
What is the function of Digoxin?
Cardiac antiarrhythmic drug that stabilizes atrial electrical activity
What does Digoxin cause?
Slows conduction of cardiac impulses through AV node which slows ventricular response in pts w/afib
What are the clinical uses of Digoxin?
Can also enhance conduction of cardiac impulses through accessory bypass tracts; can enhance conduction of cardiac impulses through accessory tracts & increase ventricular response rate in pts w/WPW
What can digoxin toxicity manifest as?
Digoxin toxicity can manifest as cardiac arrhythmias, most commonly atrial tachycardia w/block