Amiodarone

Question 1

What is the usual outcome with an amiodarone overdose?

Answer 1

Usually benign regardless of the dose ingested; no know fatalities of acute overdose.

Question 2

What are the clinical manifestations of chronic amiodarone toxicity?

Answer 2

Pulmonary toxicity, cardiovascular (brady, AV blocks, torsades, hypotension, negative inotropy), thryoid dysfunction, hepatotoxicity, corneal micro-deposits

Question 3

What Vaughn-Williams class effects does amiodarone have?

Answer 3

Predominantly class III but also class I, II, IV.

Question 4

What does class III activity translate to in terms of practice?

Answer 4

Potassium channel blockade, prolonging phase 4 of the cardiac action potential and the refractory period of atrial and ventricular tissue.

Question 5

Discuss the toxicokinetics of amiodarone.

Answer 5

Oral bioavailability is poor; protein bound with large VoD (65 L/kg). Undergoes first-pass metabolism by cytochrome P450 –> active metabolite. Elimination is biliary and slow - 80 hours to 100 days.

Question 6

What is the acute toxicity with amiodarone overdose rarely?

Answer 6

Delayed cardiac effects - hypotension, atrial flutter, TWI have been reported but clinical course is usually benign.

Question 7

Discuss recommended period of monitoring after amiodarone overdose.

Answer 7

24 hours of cardiac monitoring with serial ECGs

Question 8

What is important to know about the bradycardia associated with amiodarone overdose?

Answer 8

It may be resistant to atropine and require adrenaline, isoprenaline or pacing. Hypotension responds to vasopressors.