Amiodarone

Question 1

Amiodarone Mechanism of Action

Answer 1

• Amiodarone is an antidysrhythmic with a broad spectrum of activity.
• Amiodarone has predominantly class III activity. It prolongs the action potential duration, reduces automaticity and prolongs the refractory period of
atrial, nodal and ventricular tissues.
• The electrophysiological effects result in a reduction in abnormal electrical activity (for example ectopy), a reduction in electrical conduction, a reduction
in heart rate and a stabilisation of the SA and AV nodes.
• Amiodarone also causes a small increase in coronary blood flow (although
this is not usually clinically significant) and a reduction in myocardial oxygen
consumption by reducing inotropy (the force of cardiac contraction).

Question 2

Amiodarone Indications

Answer 2

Cardiac arrest with VF or VT at any time after the first dose of adrenaline.
Adults with sustained VT in the absence of cardiac arrest.
Adults with moderate cardiovascular compromise as a result of fast atrial
fibrillation or fast atrial flutter.

Question 3

Amiodarone Contraindications

Answer 3

Known severe allergy.
Known severe allergy to iodine.
VT secondary to cyclic antidepressant poisoning. In this setting amiodarone administration can be associated with severe worsening of shock, without resolution of the rhythm.

Question 4

Amiodarone Cautions

Answer 4

1 None if the patient is in cardiac arrest.
2 Poor perfusion or signs of low cardiac output. Amiodarone reduces inotropy and may cause a significant fall in cardiac output, particularly when
administered rapidly.
3 Hypotension. Amiodarone causes vasodilation and may worsen hypotension, particularly when administered rapidly.
4 Atrial fibrillation associated with sepsis. Amiodarone may cause a significant fall in cardiac output.
5 Known sick sinus syndrome without an internal pacemaker in place. Amiodarone slows the heart rate and severe bradycardia may occur following reversion of a tachydysrhythmia.
6 Previous 2nd or 3rd degree heart block without an internal pacemaker in place. Amiodarone slows the heart rate and severe bradycardia may occur following
reversion of a tachydysrhythmia.
7 Pregnancy.

Question 5

Amiodarone Use in pregnancy/breastfeeding

Answer 5

• May cause harm during pregnancy. Do not administer amiodarone unless
there is a strong clinical indication.
• May be administered if the patient is breastfeeding. Advise the patient to stop
breastfeeding and seek further advice from their lead maternity carer or GP.

Question 6

Amiodarone Dose

Answer 6

Cardiac arrest:
a) 300 mg for an adult.
b) If VF or VT persists, a second dose of 150 mg may be administered.
c) See the paediatric drug dose tables for a child.
• Tachydysrhythmia in an adult:
a) 300 mg IV over 30 minutes.
b) A further 150 mg IV over 30 minutes may be administered if the tachydysrhythmia persists.

Question 7

Amiodarone Common adverse effects

Answer 7

• Hypotension.
• Feeling light-headed.
• Bradydysrhythmia.

Question 8

Amiodarone Usual onset of action

Answer 8

5-10 minutes

Question 9

Amiodarone Usual Duration of action

Answer 9

• 1-4 hours after a single dose.
• Amiodarone is taken up into tissues and slowly released. This may result in a prolonged half-life, particularly when more than one dose has been
administered. This is why many references quote a half-life of 10-60 days, but the clinical duration of effect is much shorter than this.

Question 10

Amiodarone preparation

Answer 10

150mg/3mls

Question 11

Amiodarone Pharmacokinetics

Answer 11

• Amiodarone is metabolised in the liver.

* There are no significant effects from liver impairment on acute administration.

Question 12

Amiodarone Common intereractions

Answer 12

• May potentiate the action of cyclic antidepressants in cyclic poisoning.
• May cause bradycardia following reversion of dysrhythmia if the patient is taking a beta-blocker and/or a centrally acting calcium channel blocker (for
example diltiazem).