Amiodarone

Indications
 Oral
Ventricular arrhythmias
Adult: 800-1,600 mg/day in 1-2 divided doses for 1-3 wk until initial therapeutic response is achieved, then reduce dose to 600-800 mg/day in 1-2 divided doses for 1 mth. Maintenance: 400 mg/day; lower doses may be used for supraventricular arrhythmias. Daily doses may be divided. Close monitoring of the patient is recommended. Use the minimum effective dose.
Hepatic impairment: Dosage reduction may be necessary.
Intravenous
Life-threatening ventricular arrhythmias
Adult: Recommended starting dose: About 1 g over 1st 24 hr. Dose is given in a 3-phase sequence. Initial rapid loading dose: Infuse 150 mg at a rate of 15 mg/minute (initial infusion rate should not exceed 30 mg/minute); followed by the slow loading phase: Infuse 360 mg at a rate of 1 mg/minute; followed by the first maintenance phase: Infuse 540 mg at a rate of 0.5 mg/minute. After the 1st 24 hr, maintain infusion rate at 0.5 mg/minute (i.e. 720 mg over 24 hr); rate may be increased to achieve effective suppression of arrhythmia. For breakthrough episodes, supplemental doses of 150 mg may be given at 15 mg/minute; may repeat supplemental doses up to a max IV dose of 2.2 g/24 hr. Maintenance infusion at up to 0.5 mg/minute may be continued for up to 2-3 wk with caution. Concentrate for inj should be diluted prior to admin. Conversion to oral therapy will depend on the administered dose of the IV therapy and the bioavailability of the oral drug.
Hepatic impairment: Dosage reduction may be necessary.
Intravenous
Pulseless ventricular fibrillation or ventricular tachycardia
Adult: Initial: 300 mg (diluted in 20-30 ml dextrose 5% or normal saline) if VF or VT recurs, to be given as a single dose by rapid IV inj. Supplemental dose: 150 mg followed by an infusion of 1 mg/minute for 6 hr, then 0.5 mg/minute. Max: 2.1 g daily.
Hepatic impairment: Dosage reduction may be necessary.

Reconstitution: To make solution for 1st rapid loading infusion or supplemental infusion: Add 3 ml of amiodarone HCl concentrate (50 mg/ml) to 100 ml of dextrose 5% to give a final conc of 1.5 g/ml; for slow infusion: Add 18 ml of amiodarone HCl concentrate (50 mg/ml) to 500 ml of dextrose 5% to give a final conc of 1.8 mg/ml; for subsequent maintenance infusions, diluted solutions with conc ranging from 1-6 mg/ml may be used. Solutions with conc ≥2 mg/ml should be administered via a central venous catheter.
Incompatibility: Y-site incompatibility: Cefamandole, sodium bicarbonate, heparin, aminophylline. Syringe incompatibility: Heparin. Admixture incompatibility (amiodarone conc: 4 mg/ml): Cefazolin sodium, cefamandole, mezlocillin sodium, sodium bicarbonate, heparin sodium, aminophylline.
Contraindications
 Hypersensitivity to amiodarone or iodine. Severe sinus node dysfunction, 2nd and 3rd degree heart block (except in patients with a functioning artificial pacemaker), cardiogenic shock, pregnancy.
Warnings / Precautions
 Close monitoring is recommended as amiodarone may worsen arrhythmia especially when used concurrently with other anti-arrhythmic drugs or drugs that prolong QT interval. May cause hypotension and bradycardia. May increase risk of liver toxicity. May cause visual disturbance/impairment; corneal refractive laser surgery is not recommended in patients on amiodarone treatment. May cause lung damage; monitor for pulmonary toxicity e.g. acute respiratory distress syndrome. Monitor liver functions regularly. May affect defibrillation or pacing thresholds of cardiac devices. Correct electrolyte imbalance before starting treatment. Caution when used in patients undergoing surgery. Avoid excessive sunlight exposure due to increased risk of photosensitivity. Hepatic impairment, thyroid disease, elderly. Lactation.
Adverse Reactions
 Blue-grey discolouration of skin, photosensitivity, peripheral neuropathy, paraesthesia, myopathy, ataxia, tremor, nausea, vomiting, metallic taste, hypothyroidism, hyperthyroidism, alopoecia, sleep disturbances, corneal microdeposits, hot flushes, sweating. Heart block, bradycardia, sinus arrest, hepatotoxicity, heart failure.
Potentially Fatal: Pulmonary toxicity including pulmonary fibrosis and interstitial pneumonitis, hepatotoxicity, thyrotoxicity. Ventricular arrhythmias, pulmonary alveolitis, exacerbation of arrhythmias and rare serious liver injury. Generally in patients with high doses and having preexisting abnormalities of diffusion capacity.
Overdose Reactions
 Symptoms include hypotension, cardiogenic shock, bradycardia, AV block and hepatotoxicity. Hypotension and cardiogenic shock should be treated by slowing the infusion rate or with vasopressor drugs, positive inotropic agents and volume expansion. Bradycardia and AV block may require temporary pacing. Monitor hepatic enzyme concentrations. Amiodarone is not dialyzable.
Drug Interactions
 Potentiation of antiarrhythmic drugs. Possible increased risk of adverse effects when used with anaesthetic agents. Monitor plasma levels of amiodarone when used with HIV protease inhibitors. Cimetidine may increase serum levels of amiodarone. Concurrent use may increase serum levels of ciclosporin. May increase risk of myopathy or rhabdomyolysis when used with HMG-CoA reductase inhibitors. Rifampin may reduce the serum levels of amiodarone.
Potentially Fatal: Potentiates the effect of warfarin and other anticoagulants hence dose of warfarin generally needs to be reduced approx half. Raised plasma concentrations of digoxin, phenytoin and quinidine. Additive effect with beta-blockers and calcium-channel blockers (e.g. verapamil and diltiazem).
See Below for More amiodarone Drug Interactions
Food Interactions
 St John's wort may reduce serum levels of amiodarone. Grapefruit juice may increase serum levels of amiodarone.
Mechanism of Actions
 Amiodarone is a class III antiarrhythmic agent which inhibits stimulation, prolongs action potential and refractory period in myocardial tissues. It also decreases AV conduction and sinus node function. Sinus rate is reduced by 15-20%, PR and QT intervals are increased. Amiodarone can cause marked sinus bradycardia or sinus arrest and heart block. In acute IV doses, amiodarone may exert a mild negative inotropic effect.
Onset: IV: 1-30 minutes.
Duration: IV: 1-3 hr.
Absorption: Oral admin: Variable and erratically absorbed from the GI tract; average bioavailability is about 50%.
Distribution: Extensively distributed to body tissues; accumulates in muscles and fats. Crosses the placenta and enters breast milk. Protein-binding: 96%
Metabolism: Yields desethylamiodarone (also has antiarrhythmic properties); may undergo enterohepatic recycling.
Excretion: Mainly in the faeces via bile; via urine (small amounts of amiodarone and its metabolites). Terminal elimination half-life: About 50 days; may range from 20-100 days due to extensive tissue distribution.
Administration
 May be taken with or without food. (Take consistently w/ or w/o meals. Take w/ meals if high dose or to reduce GI discomfort.)
Storage Conditions
 Intravenous: Store at 15-25°C. Oral: Store at 20-25°C.
ATC Classification
 C01BD01 - amiodarone ; Belongs to class III antiarrhythmics.
Storage
 Intravenous: Store at 15-25°C. Oral: Store at 20-25°C.
Available As
  • Amiodarone 100 mg
  • Amiodarone 150 mg
  • Amiodarone 200 mg
  • Amiodarone 50 mg

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