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Tintinalli Section 3 - Resuscitation > S3C23 - Pharmacology of Antiarrhythmics > Flashcards

S3C23 - Pharmacology of Antiarrhythmics Flashcards

1
Q

Class I

A

Fast Sodium Channel Blockers
Ia: quinidine, disopyramide, procainamide
Ib: lidocaine, phenytoin, mexiletine
Ic: encainide, flecainide, propafenone, indecainide, moricizine

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2
Q

Class II

A

Beta blockers

-propranolol, metoprolol, esmolol

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3
Q

Class III

A

Potassium efflux

-breytlium, amiodarone, sotalol, dofetilide

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4
Q

Class IV

A

Calcium Channel blockers

-verapamil, diltiazem

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5
Q

Class - unclassified

A

-digoxin, adenosine, magnesium sulfate

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6
Q

Lidocaine

A

Action:

  • Class Ib antiarrhythmic
  • little effect on peripheral vascular tone, contractility, CO
  • causes CNS depression, sedation, anticonvulsant
  • stabilized membranes, elevate v fib threshold and suppresses ventricular ectopy

Pharmacokinetics:

  • onset 45-90sec
  • duration 10-20mins
  • elimination prolonged in CHF/liver dz

Indications:

  • ventricular arrhythmias and ectopy
  • second line to amiodarone for ACLS treatment of v fib and pulseless v tach

Dosing:

  • loading dose 1-1.5mg/kg
  • boluses 0.5-0.75mg/kg q5-10min
  • NMT 3mg/kg total dose, reduce by 50% if CHF/liver dz

Adverse effects:
-toxicity: slurred speech, drowsiness, confusion, nausea, psychosis, seizures, respiratory depression

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7
Q

Procainamide

A

Action:

  • Class Ia antiarrhythmic (same mechanism as quinidine) (binds to fast sodium channels)
  • suppresses fibrillatory activity in the atria/ventricles and prevents ectopic or reentrant arrhythmias
  • prolongs PR, QT, QRS
  • large dose = proarrhythmic; vasodilation leads to hypotension and sinus tachy
  • decreases force of myocardial contractility - negative inotrope

Pharmacokinetics:

  • onset 5-10mins
  • 1/2 life 4-5min (increased with CHF and renal dz)
  • metabolized to active form in the liver, active metabolite has 1/2 life of 7h

Indications:

  • ventricular arrhythmias - treat or prevent (stable VT)
  • convert SVT
  • contraindications: complete AV heart block or 2nd/3rd deg heart block (if no PM present), BBB, long QT, glycoside OD, torsades, myasthenia gravis
  • use caution in SLE, CHF, bone marrow suppression

Dosing:
-continuous infusion for ventricular arrhythmias at 20mg/min for 25 mins then at 1-4mg/min

Adverse effects:

  • QRS/QT prolongation, VT, VF, PVCs, complete AV block, torsades
  • SLE - 50% pts on procainamide produce ANA
  • agranulocytosis, leukopenia, hypoplastic anemia, thrombocytopenia
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8
Q

Propafenone

A
  • class Ic

- can be used for pill-in-the-pocket for paroxysmal a. fib (600mg) - do as in patient with first trial

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9
Q

Flecainide

A
  • class Ic
  • can be used to treat a fib/flutter with preserved LV fxn
  • 2mg/kg at 10mg/min IV
  • -can be used for pill-in-the-pocket for paroxysmal a. fib (300mg)
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10
Q

Beta Blockers

A
  • class II antiarrhythmics
  • cardioselective (specific for B1 receptors): acebutolol, atenolol, esmolol, metoprolol (better for asthmatics and diabetes)

Indications
- HTN (except sotalol/esmolol), decrease mortality in ACS (metoprolol/atenolol) and non-acute CHF (bisoprolol, carvedilol, metoprolol)

Adverse Reactions
-n/v, light-headed, depression, bradycardia, hypotension, bronchospasm, hyperglycemia, pulmonary edema

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11
Q

Esmolol

A

Actions

  • beta1 selective, short-acting
  • negative inotropic and chronotropic effects
  • increases sinus cycle, prolongs SA nodal recovery time, decreases conduction through AV node

Pharmacokinetics

  • onset 1-4mins
  • only available IV
  • 1/2 life is 9 mins (quite short)

Indications: SVT

Dosing:
-loading 500mcg/kg bolus then infusion of 50mcg/kg/min for 4 mins

Adverse Effects: hypotension, bradycardia, syncope, heart block

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12
Q

Labetalol

A

Actions:

  • class II antiarrhythmic
  • non-cardioselective beta-adrenergic blocker and selective alpha 1 blocking agent
  • decreases heart rate, contractility, cardiac output, cardiac work, total peripheral resistance

Pharmacokinetics:

  • onset 2-5 mins IV or 20min-2h PO
  • duration of action 2-4h IV and 8-24h PO

Indications: HTN
-markedly reduces BP with minimal effects on HR and CO

Dosing: 20mg IV with repeat of 40mg q10min (NMT 300mg)

  • infusion 0.5-2mg/min
  • PO: up to 2500mg/d divided BID/TID/QID

Adverse effects: orthostatic hypotn, light-headed, drowsy, nightmares

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13
Q

Propranolol

A

Actions:

  • non-cardioselective BB
  • decreases chronotropic, inotropy
  • decreased sinus rate and CO, depresses AV conduction, and decrases myocardial oxygen consumption

Pharmacokinetics:

  • onset is 1min after IV and 1h after PO
  • 1/2 life ~3h

Indications:

  • SVT (MAT), thyrotoxicosis, angina, HTN, HCM (=HOCM), migraine prophylaxis, essential tremor, anxiety, pheochr.
  • not indicated for hypertensive emergencies

Dosing:
-loading 0.5-1mg IV at 1mg/min

Adverse Effect: (same as other BB)
-contraindicated in SA/AV block and intermittent claudication, CHF

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14
Q

Sotalol

A

Actions:

  • class II antiarrhythmic - non-cardioselective BB
  • has some class III properties (prolongs repol and refractoriness w/o affecting conduction)

Pharmacokinetics:

  • onset 2-3h
  • duration 24h
  • elimination depends on renal fxn

Indications:

  • life-threatening ventricular arrhythmias
  • suppresses a fib and SVT

Dosing: 80mg PO BID
-NMT 640mg/d

Adverse Effect: bradycardia, hypotension, hyperglycemia
-can be proarrhythmic in long QT, torsades, hypokalemia

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15
Q

Amiodarone

A

Actions:

  • class III antiarrhythmic, but also traits of class I, II and IV
  • slows the heart by impairing SA node, dperesses AV node conduction, modifies purkinje firing and prolongs the refracotry period in an accessory pathway (eg. WPW)
  • inhibits potassium channels to incrase repolarization in the mycocardium, blocks fast Na channels, and decreases HR and AV node conduction by BB and CCB properties

Pharmacokinetics:

Indications: ventricular and SVT arrhythmias, VF/VT, AFib A flutter, junctional and wide complex tachy

Dosing:

  • Vfib/pulseless VT: 300mg followed by 150mg (ACLS)
  • stable VT or SVT: 150mg IV in 100cc 5% dextrose in water (D5W) over 10 mins followed by an infusion
  • cardioversion: 5-7mg/kg over 30-60min followed by infusion until total dose of 10g has been given (or PO 1.2-1.8g/d in divided doses until 10g given total) (NMT 0.9mg/d for out pt PO tx)

** before starting long-term tx must get baseline ophtho and PFT tests

Adverse effects:

  • thyroid d/o, pulmonary fibrosis, skin discoloration, hepatic dysfxn, corneal infiltrates, paroxysmal VTach, CHF
  • hypotension/bradycardia
  • CI: iodine allergy
  • MANY drug interactions (simvastatin, warfarine, dig, CCB, BB)
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16
Q

Dofetilide

A

Actions:

  • pure class III antiarrhythmic
  • prolongs repolarization without affecting conduction velocity via K+ channel inhibition
  • suppresses arrhythmias related to reentry mechanisms
  • negative chronotropy

Pharmacokinetics:

  • onset = 2h (PO)
  • duration = 4h (PO)

Indications:

  • conversion of A fib/flutter to NSR for very symptomatic pts
  • strict prescribing patterns - quite proarrhythmic

Dosing:

  • CI if QTc >440msec
  • 500mcg PO BID depending on Creatinine clearance

Adverse Effects: QTc prolongation, Vtach, h/a, dizzy, c/p

17
Q

Ibutilide

A

Actions:

  • Class III antiarrhythmic
  • prolongs action potential duration and effective refractory period
  • activates the slow inward Na current (as opposed to inhibiting the outward K+ current)

Pharmacokinetics:

  • onset 20-30mins if IV
  • duration 24h if IV

Indications:
-rapid conversion of recent onset a fib/flutter

Dosing:

  • IV only, loading dose 1mg IV in 50cc D5W over 10 mins or 0.01mg/kg IV in 50cc D5W
  • may rpt after 10 mins
  • continue ECG monitor for 4h after or until QTc normalized

Adverse Effects:
-hypotension, HTN, bradycardia, sinus arrest, syncope, QTc prolongation, CHF

18
Q

Diltiazem

A

Actions:

  • class IV antiarrhythmic - CCB
  • nondihydropyridine CCB (interfers with influx of ECF Ca+ through slow channels)
  • slows AV conduction and prolongs AV refractoriness
  • minimal systemic vasodilation, preferentially dilates the coronary vasculature
  • helps in SSS with SA automaticity

Pharmacokinetics:

  • onset IV is 2-3min (peak response 2-7min)
  • onset PO is 15-60mins (peak response 1.5-4h)
  • duration = 1-3h if IV

Indications:

  • rapid conversion of PSVT
  • slow ventricular response in A fib/flutter
  • vasospastic angina
  • HTN

Dosing:

  • load with 0.25mg/kg (max 20mg) IV over 2min, rpt in 15 mins with 0.35mg/kg if needed
  • infusion rate 5-15mg/h
  • max antihypertensive effect seen w/in 14d

Adverse effect:
-angina, bradycardia, asystole, CHF, AV block, BBB, flushing, hypotension, palpitations, edema, h/a, dizzy, nausea, constipation, rash, diarrhea, dry mouth, pruritus, insomnia, tinnitus, depression, sexual dysfxn, hyperglycemia, photosensitivity

19
Q

Verapamil

A

Actions:

  • class IV antiarrhythmic - nondihydropyridine CCB
  • substantial inhibitory effects on the cardiac conduction system as well as slowing AV node

Pharmacokinetics:

  • onset in 5 min (IV)
  • peak response 10-20 min (IV)
  • duration 30-60 min (IV)
  • PO: onset= 1-2h peak response = 4-11h duration = 6-12h

Indications:

  • as effective as adenosine in terminating narrow-complex PSVT and for controlling the ventricular response in a fib/flutter
  • angina
  • HTN

Dosing:

  • PSVT: 5-10mg IV bolus over 2mins
  • check BP before and after administration
  • consider pretreatment with CaCl/Gluconate
  • max effects seen w/in 48h
  • PO 240-280mg/d div TID for angina/HTN

Adverse Effects:
-hypotension, bradycardia, AV block, BBB, pulmonary edema, constipation, dizzy, h/a, nausea

20
Q

Atropine

A

Actions;

  • other antiarrhythmic class
  • antimuscarininc - antagonizes acetylcholine
  • increases sinus node automaticity and AV conduction by blocking vagal activity

Pharmacokinetics:
-rapid onset, peak affect 2-4min, duration up to 5h

Indications:

  • reverses cholinergic-mediated decreases in HR
  • symptomatic sinus brady, AV block

Dosing:

  • loading dose 0.5mg bolus q3min (NMT 0.04mg/kg)
  • PEA/asystole 1mg rapid IV bolus q3min
  • IV/IM/ET/SC/IO (if ET then increase dose by 2x)

Adverse effect:
-anticholinergic symptoms - blurred vision, dry mouth, hallucinations, mydriasis, tachycardia

21
Q

Adenosine

A

Actions:

  • transient negative inotropic, dromotropic, chronotropic effects on SA and AV nodal tissues
  • transient AV nodal block, breaks a reentrant circuit involving the AV node

Pharmacokinetics:

  • onset 20-30sec
  • duration 60-90sec
  • metabolized by adenosine deaminase to inosine

Indications:

  • SVT
  • contraindicated: 2nd/3rd deg heart block or SSS if no PM present
  • NOT effective for converting a fib/flutter

Dosing: 6mg over 1-2sec then 12mg if need repeating (x2)

Adverse effect:
-dyspnea, cough, syncope, vertigo, paresthesias, numbness, nausea, metallic taste, flushing, h/a, palpitiations, c/p, sinus brady, PVC, hypotension

22
Q

Digoxin

A

Actions:

  • increases force, strength, velocity of cardiac contractions (positive inotropy)
  • slow HR (negative chronotropic)
  • slows conduction velocity through AV node (negative dromotropy)
  • inhibits NaK+ATPase enzyme pump system, leads to loss of K+ in ICF in increase in Na+, which causes influx of Ca+ through Na/Ca pump, this improves contractions
  • increases conduction in accessory paths therefore do not use in WPW

Pharmacokinetics:

  • onset 5-30mins IV and 30-120mins PO
  • peak effect 1.5-4h IV and 4h PO
  • dialysis is ineffective in removing dig

Indications:

  • improves CO in CHF, reduces hospitilization for CHF but not mortality
  • controls ventricular response in a fib/flutter/PSVT

Dosing:

  • 0.125-0.375mg OD PO
  • serum level target of 0.8-2 nanograms/ml
  • IV: 0.25mg q2h NMT 1.5mg

Adverse effects: (mostly GI)

  • abdo pain, diarrhea, n/v, gynecomastia, rash, eosinophilia, thrombocytopenia, arrhythmias
  • dig toxicity: mental status change, confusion, h/a, drowsy, anorexia, n/v, weak, visual disturbance, delirium, seizure, hyperkalemia
  • digibind/digifab indicated for tachyarrhythmia, sinus brady, severe AV block, K+ >5mEq/L
23
Q

Isoproterenol

A

Actions:

  • sympathomimetic agonist (beta 1 and beta 2)
  • increased chronotropy and inotropy and vasodilation

Pharmacokinetics:

  • onset 1-5min
  • duration 1-2h

Indications:
-refractory torsades and temporary control of refractory symptomatic brady

Dosing: 2-10mcg/min IV infusion

Adverse Effect: ischemia

24
Q

Magnesium

A

Actions:

  • increases skeletal and smooth msc contractility, vasomotor tone, neuronal transmission
  • activates NaK+ATPase pump and does some CCB
  • prolongs AV, increases refractory period

Pharmacokinetics:
-duration 30mins IV

Indications:

  • torsades
  • refractory VTach, VFib
  • seizures: toxemia, eclampsia, nephritis, hypomagnesema, acute asthma exac

Dosing: 1-4g in 50-100cc D5W over 20-60 mins
-or 1-2g IV bolus in 10cc D5W over 1-2min if arrested

Adverse effect:

  • hypotension
  • flushing, sweating, n/v, CNS, depressed DTR, paralysis, depressed cardiac vxn, resp dpn, circulatory collapse

Tintinalli Section 3 - Resuscitation (10 decks)

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