Amiodarone

• Amiodarone is an extremely useful and often effective anti-arrhythmic drug.
• It is, however, a difficult drug to use with a long half-life and a potentially serious side-effect profile, and should only be prescribed after careful evaluation of the risks and potential benefits.
• It should almost never be used for patients with atrioventricular re-entrant tachycardia or atrioventricular nodal re-entrant tachycardia ('junctional’ tachycardias) but is sometimes useful for patients with paroxysmal atrial fibrillation/flutter/atrial tachycardia, usually if other drugs have failed or are contra-indicated.
• It is sometimes useful for the treatment of ventricular tachycardia but blanket use of amiodarone for the treatment of ventricular arrhythmias is to be discouraged. Consult a cardiologist if necessary.
• It is inappropriate for the treatment of torsades de pointes or if QT interval is prolonged.

Intravenous loading

Amiodarone should be administered via a central line ideally but can be given through large peripheral vein in an emergency if the cannula is reliably placed.

• 300mg infused over 20 minutes to two hours (during which time arrangements for PICC line or central line should be made for the continued infusion. Peripheral infusion can lead to serious tissue necrosis) followed by 900mg over the next 24 hours.
• If amiodarone is to be given for suppression of ventricular arrhythmias, intravenous loading may need to be continued for up to 7 days with 900mg of amiodarone administered every 24 hours.
• In an extreme emergency 150 to 300mg can be given as an intravenous bolus over one to two minutes.
• The initial dose of amiodarone should be made up as 300mg in 250ml 5% dextrose and given over 20 minutes - 2 hours.
• This may be followed by a repeat infusion of 900mg in 500ml 5% dextrose over 24 hours infused at a rate of 21ml/hr.
• If intravenous loading is to exceed 24 hours it must be administered via a central line. 

An alternative loading strategy

• For inpatients give 400mg orally three times a day for one week: recommended for VT.
• Reduce to 200mg twice daily for one week and thereafter a maintenance dose of 200mg once daily.

Commence as soon as possible following intravenous therapy at a dose of 200mg three times daily for one week, then 200mg twice daily for one week and thereafter a maintenance dose of 200mg daily.

• Severe conduction disorders or sinus node disease without a pacemaker.
• Caution should be exercised in patients with known thyroid dysfunction.
• Iodine hypersensitivity.
• Inform the patient of side effects such as skin photosensitivity, hyperthyroidism and hypothyroidism, pulmonary fibrosis, peripheral neuropathy and hepatic dysfunction.
• Corneal micro-deposits are very common and hardly ever cause a clinical problem.
• Baselines measurements of thyroid function (TFT’s) and liver function tests (LFT’s) should be made, as should a baseline chest X-ray. Check TFT’s and LFT’s every 6 months in longterm treatment.
• Medical staff and patients should be aware that any unexplained breathlessness or cough should be promptly investigated to exclude amiodarone lung toxicity.
• Avoid long term use of Amiodarone wherever possible. For patients with paroxysmal atrial fibrillation, a new alternative - dronedarone, could be used after discussion with cardiology.

These are not uncommon and are often clinically significant.

• Particularly important interactions include elevation of digoxin levels and attenuation of the anticoagulant effects of warfarin. The dose of digoxin should be halved and warfarin requirements may decrease by 30-50%.
• The maximum recommended dose of simvastatin is 20mg when used concomitantly with amiodarone.
• Advise patients to moderate alcohol intake and avoid grapefruit juice.
• Amiodarone on occasions can cause pro-arrhythmia, both bradycardia and tachycardia.