Makindo Medical Notes

Important: Side effects of Amiodarone can be severe. Long-term treatment is typically specialist-initiated for life-threatening arrhythmias or situations where no safer alternative exists. Though Amiodarone is a highly effective antiarrhythmic (with Class III properties), it is irritant and extravasation can be serious. Patients should be fully counseled regarding the potential risks of long-term therapy.

About: Always check the BNF link here

• Amiodarone is a very useful antiarrhythmic, but side effects can be significant.
• Long-term therapy should be initiated by a specialist only.

Mode of Action

• Primarily a potassium channel blocker (Class III effect).
• Also blocks sodium and calcium channels.
• Prolongs action potential duration and the effective refractory period.
• Exhibits some alpha- and beta-blocking activity.
• Has vagolytic properties and slows conduction in the His–Purkinje system.
• Slows conduction in the accessory pathway of patients with Wolff–Parkinson–White syndrome.
• Also acts as a potent vasodilator.

Pharmacokinetics

• Structurally similar to thyroxine and contains iodine.
• Has vasodilatory effects; originally marketed as an antianginal.
• Accumulates in fat and muscle.
• Metabolized in the liver to its active form, desethylamiodarone.
• Very long half-life (20–100 days), which can be longer in the elderly.

Indications

• Ventricular arrhythmias and atrial fibrillation.
• Emergency treatment of wide complex tachycardia.

Contraindications

• Thyroid dysfunction.
• AV block, sinus bradycardia (without a pacemaker).

Side Effects

• Bradycardia; sinus node or AV node conduction block.
• Negative inotropic effect (though less than most other antiarrhythmics).
• Thyroid disease — hypothyroidism or hyperthyroidism.
• Torsade de Pointes and prolonged QT interval.
• Pulmonary toxicity, including interstitial pneumonitis, alveolitis, and fibrosis.
• Retroperitoneal fibrosis (rare).
• Tremor, ataxia, cutaneous photosensitive rash.
• Skin pigmentation changes (slate-grey appearance), photosensitivity.
• Orchitis, hepatitis.
• Reversible corneal micro-deposits (usually harmless).
• Peripheral neuropathy.
• Hypotension if administered too rapidly via IV.

Interactions

• Increases INR when used with Warfarin.
• Can increase the toxicity of Digoxin and Phenytoin.
• Multiple other interactions — see BNF for full details.

Dose Range: You must check the BNF or drug datasheet

Name	Starting Dose	Frequency	Route
Amiodarone (Cardiac Arrest)	300 mg	Stat	IV in 20–30 ml of NS or D5W, usually after the 3rd shock.
Amiodarone (Arrhythmias)	150–300 mg	Stat	Slow IV in 250 ml of 5% dextrose over 30–60 mins.
Amiodarone (Arrhythmias Loading IV)	900 mg	Over 24 hours	Slow IV in 250 ml of 5% dextrose over 24 hours in 500 ml of 5% dextrose via a central line.
Amiodarone (Oral Loading)	200 mg	OD	Oral loading: 200 mg TDS for 1 week, then BD for 1 week, then OD.

Dosing Details & Monitoring

• Cardiac Arrest (VF/Pulseless VT): Amiodarone 300 mg IV in 20–30 ml of NS or D5W, usually after the 3rd shock. It is irritant; extravasation can be serious, so use central access where possible. Flush with 20 ml of 5% dextrose (or NS), preferably through a central line or large-bore cannula.
• Arrhythmias (Acute Use): Amiodarone 300 mg IV in 250 ml of 5% dextrose over 30–60 mins into a large proximal vein.
  Follow with an additional 900 mg over 24 hours in 500 ml of 5% dextrose by central line.
  If there is arrhythmia-induced angina or hypotension, administer the initial dose more rapidly and be prepared to defibrillate if necessary.
• Long-Term Treatment: Amiodarone 200 mg PO TDS for one week, then 200 mg BD for one week, then 200 mg OD.
• Monitoring: Check U&E and thyroid function tests (TFTs) at baseline and every 6 months. Watch for shortness of breath; if present, get a CXR to assess for pulmonary complications.
• Photosensitivity: Use sunblock to reduce the risk of photosensitive skin reactions.

References

• Amiodarone in BNF