Amiodarone

Question 1

What class of drug is amiodarone and how does it work?

Answer 1

It is a class III antiarrhythmic agent.

It blocks potassium channels which inhibits repolarisation and hence prolongs the action potential.

Question 2

How should we monitor amiodarone?

Answer 2

Prior to treatment - TFT, LFT, U&Es and CXR

Every 6 months - TFT, LFT

Question 3

What are some side effects of amiodarone?

Answer 3

• Thyroid dysfunction
• Corneal deposits
• Pulmonary fibrosis/pneumonitis
• Liver fibrosis/hepatitis
• Peripheral neuropathy, myopathy
• Photosensitivity
• ‘Slate-grey’ appearance
• Thrombophlebitis and injection site reactions
• Bradycardia

Question 4

What can amiodarone do to an ECG?

Answer 4

prolong the QT interval.

Question 5

What are 2 important drug reactions that amiodarone has?

Answer 5

1. Decreased metabolism of warfarin (increases INR)
2. Increased digoxin levels.

Question 6

What ratio of patients taking amiodarone will develop thyroid dysfunction?

Answer 6

1 in 6

Question 7

Amiodarone can cause wither hypothyroidism or thyrottoxicosis.

How does amiodarone induce hypothyroidism (AIH)?

Answer 7

Amiodarone has a high iodine content and thus thyroxine formation is inhibited due to high levels of circulating iodide. (Wolff-Chaikoff effect)

Question 8

Should amiodarone be stopped in AIH?

Answer 8

No, it can be continued.

Question 9

Amiodarone-induced thyrotoxicosis (AIT) is divded into 2 categories. Describe the pathophysiology, presentation and management of both AIT type 1 and AIT type 2.

Answer 9

AIT Type 1

• Pathophysiology - excess iodine-induced thyroid hormone synthesis.
• Goitre is present.
• Management - carbimazole or potassium perchlorate.

AIT type 2

• Amiodarone-related destructive thyroiditis.
• Goitre is absent.
• Management - corticosteroids.

Question 10

Should amiodarone be stopped in AIT?

Answer 10

Yes if possible.

It is not stopped in AIH.