a·mi·o·da·rone hydrochloride ( -m   -d-rn )n. A vasodilator for the heart used to control ventricular and supraventricular arrhythmias and to manage stenocardia. |
amiodarone hydrochloride,
amiodarone hydrochloride
Amyben (UK), Cordarone, Cordarone X (UK), Pacerone
Pharmacologic class: Adrenergic blocker
Therapeutic class: Antiarrhythmic (class III)
Pregnancy risk category D
FDA Boxed Warning
• Because of substantial toxicity, drug is indicated only in patients with life-threatening arrhythmias.
• Drug may cause potentially fatal pulmonary toxicities, including hypersensitivity pneumonitis and interstitial/alveolar pneumonitis. Pulmonary toxicity is fatal about 10% of time.
• Hepatic injury is common but usually mild, manifesting only as abnormal liver enzyme levels. However, overt hepatic disease can occur and, in rare cases, is fatal.
• Drug may exacerbate arrhythmias by reducing tolerance for them or making them harder to reverse. Arrhythmias and significant heart block or sinus bradycardia occur in 2% to 5% of patients.
• Even in patients at high risk for arrhythmic death in whom toxicity is an acceptable risk, drug poses major management problems. Therefore, other agents should be tried first whenever possible.
• Difficulty of using drug effectively and safely poses significant risk. Patients with indicated arrhythmias must be hospitalized to receive loading dose; response generally takes at least 1 week, but usually 2 or more.
Action
Prolongs duration and refractory period of action potential. Slows electrical conduction, electrical impulse generation from sinoatrial node, and conduction through accessory pathways. Also dilates blood vessels.
Availability
Injection: 50 mg/ml in 3-ml ampules
Tablets: 200 mg, 400 mg
⊘Indications and dosages
➣ Life-threatening ventricular arrhythmias
Adults: 150 mg in 100 ml of dextrose 5% in water (D5W) by rapid I.V. infusion over 10 minutes; then dilute 900 mg in 500 ml of D5W and administer 360 mg by slow I.V. infusion over next 6 hours; then 540-mg I.V. maintenance infusion over next 18 hours. Or 800 to 1,600 mg P.O. daily in one to two doses for 1 to 3 weeks; then 600 to 800 mg P.O. daily in one to two doses for 1 month; then 400-mg P.O. daily as maintenance dosage.
Off-label uses
• Atrioventricular (AV) nodal reentry tachycardia (with parenteral use)
• Conversion of atrial fibrillation to normal sinus rhythm
Contraindications
• Hypersensitivity to drug
• Cardiogenic shock
• Second- or third-degree AV block
• Marked sinus bradycardia
• Breastfeeding
• Neonates
Precautions
Use cautiously in:
• electrolyte imbalances, severe pulmonary or hepatic disease, thyroid disorders
• history of heart failure
• elderly patients
• pregnant patients
• children.
Administration
☞ Know that I.V. amiodarone is a high-alert drug.
☞ Give loading dose only in hospital setting with continuous ECG monitoring.
• Administer oral loading dose in two equal doses with meals. Give maintenance dose daily or in two divided doses to minimize GI upset.
• Don't give I.V. unless patient is on continuous ECG monitoring.
• Dilute I.V. drug with dextrose 5% in water and use in-line filter. Drug isn't compatible with normal saline solution.
• Use central venous catheter when giving repeated doses. If possible, use dedicated catheter for drug.
| Route | Onset | Peak | Duration |
| P.O. | Variable | 3-7 hr | Wks-mos |
| I.V. | Hrs | Unknown | Variable |
Adverse reactions
CNS: dizziness, fatigue, headache, insomnia, paresthesia, peripheral neuropathy, poor coordination, involuntary movements, tremor, sleep disturbances
CV: hypotension, heart failure, worsening arrhythmia, AV block, sinoatrial node dysfunction, bradycardia, asystole, cardiac arrest, cardiogenic shock, electromechanical dissociation, ventricular tachycardia
EENT: corneal microdeposits, corneal or macular degeneration, visual disturbances, dry eyes, eye discomfort, optic neuritis or neuropathy, scotoma, lens opacities, photophobia, visual halos, papilledema
GI: nausea, vomiting, constipation, abdominal pain, abnormal salivation, anorexia
GU: decreased libido
Hematologic: coagulation abnormalities, thrombocytopenia
Hepatic: nonspecific hepatic disorders, hepatic dysfunction
Metabolic: hypothyroidism, hyperthyroidism
Respiratory: cough, adult respiratory distress syndrome, pulmonary inflammation or fibrosis, pulmonary edema
Skin: flushing, photosensitivity, toxic epidermal necrolysis
Other: abnormal taste and smell, edema, fever, Stevens-Johnson syndrome
Interactions
Drug-drug. Anticoagulants: increased prothrombin time (PT)
Beta-adrenergic blockers: increased risk of bradycardia and hypotension
Calcium channel blockers: increased risk of AV block (with verapamil, diltiazem) or hypotension (with any calcium channel blocker)
Cholestyramine: decreased amiodarone blood level
Cimetidine, ritonavir: increased amiodarone blood level
Class I antiarrhythmics (disopyramide, flecainide, lidocaine, mexiletine, procainamide, quinidine): increased blood levels of these drugs, leading to toxicity
Cyclosporine: elevated cyclosporine and creatinine blood levels
Dextromethorphan: impaired dextromethorphan metabolism (with amiodarone therapy of 2 weeks or longer)
Digoxin: increased digoxin blood level, leading to toxicity
Fentanyl: increased bradycardia, hypotension
Fluoroquinolones: increased risk of life-threatening arrhythmias
Methotrexate: impaired methotrexate metabolism, possibly causing toxicity (with amiodarone use longer than 2 weeks)
Phenytoin: decreased amiodarone blood level or increased phenytoin blood level (with amiodarone use longer than 2 weeks)
Theophylline: increased theophylline blood level (with amiodarone use longer than 1 week)
Drug-diagnostic tests. Kidney function tests: abnormal results
Drug-food. Grapefruit juice: increased drug concentration
Drug-herb. St. John's wort: decreased drug blood level
Patient monitoring
☞ Monitor patient closely. Drug may cause serious or life-threatening adverse reactions.
☞ Watch for slow onset of life-threatening arrhythmias, especially after giving loading dose.
☞ Monitor ECG continuously during loading dose and when dosage is changed.
• Check patient's blood pressure, pulse, and heart rhythm regularly.
• Assess for signs and symptoms of lung inflammation.
• Monitor baseline and subsequent chest X-rays, as well as pulmonary, liver, and thyroid function test results.
• Closely monitor patient who's receiving other drugs concurrently because amiodarone can interact with many drugs. Check digoxin blood level if patient is receiving digoxin; monitor PT or International Normalized Ratio if patient is receiving anticoagulants.
Patient teaching
☞ Inform patient that drug may cause serious adverse reactions. Instruct him to report these immediately.
• Tell patient to take oral doses with meals. Advise him to divide daily dose into two doses if drug causes GI upset.
• Tell patient that adverse reactions are most common with high doses and may become more frequent after 6 months of therapy.
• Inform patient that he'll undergo regular blood testing, chest X-rays, and pulmonary function tests during therapy.
• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs and tests mentioned above.
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