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Medicines Monitoring

Amiodarone monitoring

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Topics: AmiodaroneMonitoring
Using this page · Individualise medicines monitoring

This medicines monitoring page has been written using publications and expert opinion. It is designed to save clinician time, but not replace professional responsibility. When using this page you should: ensure an individualised monitoring plan is developed in partnership with the patient and take account of any locally agreed advice and guidance.

Contents
  1. Before starting
    1. Required
    2. Consider
  2. Continued until stable
    1. Consider
    2. Warfarinised patients
  3. Ongoing once stable
    1. Required
    2. Consider
    3. Thyroid dysfunction suspected
    4. Visual symptoms present
  4. Abnormal results
    1. Hypothyroidism
    2. Hyperthyroidism
    3. Liver function
    4. Eye problems
    5. Lung problems
  5. Notes
    1. Continuing TFTs after stopping amiodarone
  6. Bibliography

Before starting

Required

  • Baseline
    • Chest x-ray
    • ECG
    • Urea and electrolytes
    • Serum potassium
    • Liver function testsparticularly transaminases
    • T3
    • T4
    • Thyroid stimulating hormone

Consider

  • Once
    • Thyroid peroxidase antibodies

Using thyroid peroxidase antibodies

Thyroid peroxidase antibodies 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 testswhere results are borderline

Warfarinised patients

  • Weekly for at least 7 weeks
    • INR

Ongoing once stable

Required

  • 6 monthly
    • Liver function tests
    • Thyroid function tests

Consider

  • 6 monthly
    • Urea and electrolytesespecially if patient takes concomitant diuretics
  • Annually
    • Chest x-ray
    • ECG

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/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 again 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

High circulating free T4 is associated with high or high/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

Eye problems

If blurred or decreased vision occurs, complete ophthalmologic examination, including fundoscopy, should be performed promptly.
Appearance of optic neuropathy and/or optic neuritis requires amiodarone withdrawal due to the potential progression to blindness; seek expert opinion.

Lung problems

If pulmonary toxicity is suspected, chest X ray should be repeated and lung function tested, including where possible, measurement of transfer factor. Specialist referral advised.
Pneumonitis should always be suspected if new or progressive shortness of breath or cough develops in a patient taking amiodorone.

Notes

Continuing TFTs after stopping amiodarone

After stopping amiodarone, continue TFT testing for up to 12 months. This is particularly important in the elderly.

Bibliography

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