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Dr. Ajith Kumar J MD
Dept. of Emergency Medicne
Travancore Medicity, Kollam
India
editor
Amiodarone is a class III antiarrythmi agent but exhibits properties of class I, II & IV antiarrythmic properties.
Action
Amiodarone slows heart rate by impairing SA node function, depressing AV nodal conduction, modifying automaticity of spontaneously firing fibres in the purkinje system.
Prolongs refractory period in the an accessory pathway.
Amiodarone prolongs atrial and ventricular repolarisation via inhibition of potassium channels.
Amiodarone has a weak sodium channel blocker effect . It slows upstroke velocity of phase 0 which reduces the rate of membrane depolarisation and impulse conduction.
Amiodarone non competitively inhibits alpha and adrenergic receptor and posses both vagolytic and calcium channel blocking properties.
The relaxses both smooth and cardiac muscle causing decrease in coronary and peripheral vascular resistance , left ventricular end diastolic pressure and systolic pressure.
Pharmacokinetics
Amiodarone is 96 % protein bound.
It is metabolised in liver and eliminated by biliary excretion.
Terminal half life is 25 days after IV therapy. Chronic oral therapy half life increases upto 40 – 55 days
Indication
VF/ Pulse less VT
VT
Wide complex tachyarrythmia
Cardioversion of AF
Dose
ACLS dose for VF/pulse less VT : 300 mg IV bolus ; 2nd after 3 – 5 min 150 mg IV
VT : Amiodarone : 150mg IV over 10min, 1mg/min for 6hrs then 0.5mg/min ; Max dose over 24hrs: 2.2gm
Alternatively oral loading dose of 800 -1600mg/day for 1-3 weeks until a therapeutic response occurs and then oral maintenance dose of 200 – 600 mg/day
Maintence of sinus rhythm in AF :
Oral : 400 – 600 mg daily in divided doses for 2 – 4 weeks; maintence typically 100 – 200mg OD
IV : 150 mg over 10 min; then 1 mg/min for 6hrs; then 0.5 mg/min for 18 hr or change to oral dosing; after 24h consider decreasing dose to 0.25 mg/min.
Availability
Inj Cordarone 150 mg
T. cordarone 100mg, 200 mg
Adverse Effect
CVS : Hypotension, cardiac arrest, asystole, CCF
Pulmonary : Pulmonary fibrosis, interstial pneumonitis or alvelolitis ,
CNS : Peripheral neuropathy, tremors, involuntary movement
GI: Hepatitis, elevated liver enzymes
Ocular: corneal microdeposits, optic neuropathy and or neuritis, blurring of vision, blindness
Metabolic: Hypothyroidism, hyperthyroidism
Dermatologic: Photosensitivity
Warnings
Contraindicated in patients with shelfish allergy or with an iodine.
Amiodarone can decrease warfarin metabolism by 50% and a subsequent risk of bleeding.
Amiodarone increase serum concentration of digoxin, procainamide, quinidine, theophylline.
Concurrent use of amiodarone with calcium channel blocker or beta blocker may potemtiate sinus bradycardia, sinus arrest and AV block.
CO administration of simvastatin is associated with an increased risk of rhabdomyolysis.
Note :
Inj amiodarone is compatible only in 5% dextrose.
Typically for an infusion 900mg (6amp) is added to 450 ml of 5% dextrose at infued at 30 ml/hr (1mg/min) for 6 hrs and then 15 ml/hr (0.5mg/min) .
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emmedonline
Dr. Ajith Kumar J MD
Dept. of Emergency Medicne
Travancore Medicity, Kollam
India
editor