Amiodarone

Question 1

What is amiodarone?

Answer 1

Amiodarone is a class III antiarrhythmic agent used in the treatment of atrial, nodal and ventricular tachycardias

Question 2

Mechanism of action amiodarone?

Answer 2

The main mechanism of action is by blocking potassium channels which inhibits repolarisation and hence prolongs the action potential. Amiodarone also has other actions such as blocking sodium channels (a class I effect)

Question 3

What factors is use of amiodarone limited by?

Answer 3

The use of amiodarone is limited by a number of factors

very long half-life (20-100 days). For this reason, loading doses are frequently used
should ideally be given into central veins (causes thrombophlebitis)
has proarrhythmic effects due to lengthening of the QT interval
interacts with drugs commonly used concurrently (p450 inhibitor) e.g. Decreases metabolism of warfarin
numerous long-term adverse effects (see below)

Question 4

Monitoring?

Answer 4

Monitoring of patients taking amiodarone
TFT, LFT, U&E, CXR prior to treatment
TFT, LFT every 6 months

Question 5

Adverse effects amiodarone?

Answer 5

Adverse effects of amiodarone use

thyroid dysfunction: both hypothyroidism and hyper-thyroidism
corneal deposits
pulmonary fibrosis/pneumonitis
liver fibrosis/hepatitis
peripheral neuropathy, myopathy
photosensitivity
‘slate-grey’ appearance
thrombophlebitis and injection site reactions
bradycardia
lengths QT interval