Before starting

Required

• Baseline
  • Chest x-ray
  • ECG
  • Liver function tests · particularly transaminases
  • Serum magnesium
  • Serum potassium
  • Thyroid function tests · T3, T4, thyroid stimulating hormone (TSH)
  • Urea and electrolytes

Consider

• Once
  • Thyroid peroxidase antibodies

Using thyroid peroxidase antibodies

Thyroid peroxidase antibodies (TPO) can be used to help determine risk of thyroid dysfunction prior to or during amiodarone therapy. Their presence usually precedes the development of thyroid disorders.

Continued until stable

Consider

• Every 6 weeks
  • Thyroid function tests · where results are borderline

Warfarinised patients

• Weekly for at least 7 weeks
  • INR

Ongoing once stable

Required

• 6 monthly
  • Liver function tests
  • Serum magnesium
  • Serum potassium
  • Thyroid function tests
  • Urea and electrolytes
• Annually
  • ECG

Pulmonary toxicity suspected

• Once
  • CT scan

Thyroid dysfunction suspected

• Once
  • Thyroid stimulating hormone

Visual symptoms present

• Annually
  • Ophthalmological examination

Ophthalmological examination required if visual symptoms occur; however, due to the potential for micro-deposits affecting vision, patients should be encouraged to visit an optician once a year.

Abnormal results

Hypothyroidism

In clinically euthyroid patients, amiodarone may cause isolated biochemical changes (increase free-T4, slight decrease or normal free-T3).  However, there is no reason to discontinue unless there is clinical or further biological (TSH) evidence of thyroid disease.

The following advice is available:

Free T4 is low; TSH is greater than 4.5 mU/L

Consider treating with levothyroxine if amiodarone is considered essential.

Free T4 is normal; TSH is greater than 10 mU/L; duration is over 6 months

Consider treating with levothyroxine or repeat in 3 months.

Free T4 is elevated; TSH is greater than 4.5 mU/L; duration is less than 3 months

Observe and repeat in 3 months.

Hyperthyroidism

The following advice is available:

High circulating free T4 is associated with high or high or normal free T3 and undetectable TSH

• a diagnosis of amiodarone-associated hyperthyroidism is possible
• withdraw amiodarone and seek specialist referral
• clinical recovery usually occurs within a few months but precedes normalisation of TFTs
• severe cases, sometimes resulting in fatalities, have been reported

TSH is less than 0.1 mU/L, and T3 and T4 normal or minimally increased

• repeat test in 2-4 weeks

TSH is less than 0.1 mU/L and T4 elevated, T3 elevated or 50% greater than baseline

• discuss urgently with a specialist who may advise amiodarone withdrawal
• arrange for TSH-receptor antibodies and TPO antibodies

Liver function

Treatment should be discontinued if severe liver function abnormalities or clinical signs of liver disease develop.

The following advice is available:

Serum transaminases more than 3 times upper limit of normal; no symptoms of hepatic injury

Continue amiodarone and repeat liver function tests in 2 weeks. If still elevated, may require dose reduction; discuss with specialist.

Serum transaminases more than 5 times upper limit of normal or any symptoms of hepatic injury

Stop amiodarone. Urgently refer to initiating specialist and hepatologist.

Eye problems

If blurred or decreased vision occurs, complete ophthalmologic examination, including fundoscopy, should be performed promptly.

Appearance of optic neuropathy or optic neuritis requires amiodarone withdrawal due to the potential progression to blindness; seek expert opinion.

Lung problems

Routine lung imaging is not necessary. If pulmonary toxicity is suspected, consider pulmonary function tests and a CT scan (which may be more useful in confirming a diagnosis than a chest x-ray). Specialist referral advised.

Pneumonitis should always be suspected if new or progressive shortness of breath or cough develops in a patient taking amiodarone.

Cardiovascular effects

The following advice is available:

Bradycardia

Heart rate less than or equal to 50 bpm, or less than or equal to 60 bpm and symptomatic – seek specialist advice

Heart rate 50 to 60 bpm and not symptomatic – monitor heart rate; no action required unless symptoms develop or heart rate decreases further

Worsening of arrhythmia, new arrhythmia or heart block

Stop amiodarone; seek specialist advice

Electrolyte imbalances

Hypokalaemia or hypomagnesaemia, refer to Treating acute hypokalaemia in adults or Treating acute hypomagnesaemia in adults, alternatively, correct as per local guidance and continue amiodarone.

After stopping

Required

• 6 monthly
  • Thyroid function tests · for up to 12 months

Bibliography

• All Wales Medicines Strategy Group. Prescribing of amiodarone for atrial fibrillation and atrial flutter in Wales. Aug 2010, updated Sept 2016
• Association for Clinical Biochemistry (ACB), the British Thyroid Association (BTA) and the British Thyroid Foundation (BTF). UK Guidelines for the use of thyroid function tests. Jul 2006
• British Medical Journal Journals. Using oral amiodarone. Drug and Therapeutics Bulletin 2003;41:9-12.
• Ennogen Pharma Ltd. Summary of Product Characteristics- Amiodarone Hydrochloride 200mg Tablets. Last revised 14/02/2023 [cited 19/11/2024]
• Joint Formulary Committee. British National Formulary (online) London: BMJ Group and Pharmaceutical Press [cited 19/11/2024]
• Medicines and Healthcare products Regulatory Agency. Amiodarone (Cordarone X): reminder of risks of treatment and need for patient monitoring and supervision. 15/03/2022, updated May 2022
• Newman CM, Price A, Davies DW, et al. Amiodarone and the thyroid: a practical guide to the management of thyroid dysfunction induced by amiodarone therapy. Heart 1998;79:121–127
• NHS England. National Shared Care Protocol – Amiodarone. 04/07/2022
• Smellie WSA, Coleman JJ. Pitfalls of testing and summary of guidance on safety monitoring with amiodarone and digoxin. BMJ. 2007;334:312-5
• Smellie WSA, Forth J, Sundar S, et al. Best practice in primary care pathology: review 4. J Clin Pathol. 2006;59(9):893–902

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