Amiodarone

Question 1

What is amiodarone?

Answer 1

antianginal antiarrhythmic drug which increases duration of ventricular and atrial muscle action

Question 2

What class of drugs does amiodarone belong to?

Answer 2

Class III antiarrhythmic agents

Question 3

What are other drugs belonging to the same class as amiodarone?

Answer 3

sotalol, dronedarone, propafenone, flecainide acetate

Question 4

What is amiodarone indicated for?

Answer 4

paroxysmal supraventricular
nodal and ventricular
atrial fibrillation and flutter
ventricular fibrillation
tachyarrhythmias associated with wolff-parkinson-white syndrome

Question 5

What is the significance of amiodarone and thyroid disease?

Answer 5

amiodarone use (especially chronic use) can cause hyperthyroidism through a multifactorial process.

• amiodarone tablets contain iodine which is released as free iodine (higher than recommended daily intake)
• Increases thyroid hormone production and release
• long term use is associated with thyroid tissue destruction resulting in upregulated release of pre-formed thyroid hormone into circulation

Question 6

What is the mechanism of action of amiodarone?

Answer 6

Two major actions:

1) prolongs myocardial cell action potential phase 3, and the refractory period
2) acts as noncompetitive a- and b- adrenergic inhibitor

through binding to the Na/K ATPase

Question 7

What are the relevant PD/PK parameters with amiodarone?

Answer 7

• slow, variable absorption
• > 96% bound to plasma proteins
• extensively metabolised via CYP2C8
• major metabolite (desethylamiodarone) also has antiarrhythmic properties
• metabolism inhibited by grapefruit juice

Question 8

What are the precautions with amiodarone use?

Answer 8

pulmonary toxicity
hyperthyroidism
hypokalaemia
heart failure
elderly
severe bradycardia

Question 9

What are the contraindications with amiodarone use?

Answer 9

(except in cardiac arrest)
-sinus bradycardia, SA block (unless pacemaker fitted, avoid in severe conduction disturbances or SN disease
thyroid dysfunction, iodine sensitivity
hepatic impairment
pregnancy class C as possible risk of neonatal goitre only use if no alternative

Question 10

What are the adverse effects with amiodarone use?

Answer 10

nausea, vomiting, taste disturbances
jaundice
bradycardia
pulmonary toxicity (including pneumonitis andfibrosis
tremor
sleep disorders, hypothyroidism, hyperthroidism,
reversible corneal microdeposits, phototoxicity, persistent slate-grey skin discolouration
injection site reactions

Question 11

What are the relevant interactions with amiodarone?

Answer 11

Avoid concurrent use with ajmaline, amisulpride, apomorphine, chloroquine, citalopram, domperidone, methadone, moxifloxacin, due to prolongation of QT interval. (theoretical)

also avoid with atorvastatin as may increase incidence of myopathy (also theoretical)

digoxin can raise amiodarone levels (reduce digoxin by 30-50% initially and monitor

Question 12

What are the alarm bells with amiodarone use?

Answer 12

pulmonary function tests (incl. DLCO) 
LFT
TFT
serum potassium concentration
chext xray 

all to be completed before treatment