Objective: Amiodarone is an iodine rich, potent antiarrhythmic drug that is highly lipid soluble and total body iodine stores remain increased for up to 9 months. Abnormal thyroid functions, either thyrotoxicosis or hypothyroidism occur in upto 1418% of patients receiving long-term amiodarone therapy. Hence regular thyroid function tests are required in patients on long-term amiodarone treatment. The BNF clearly states that thyroid function tests should be done at a minimum 6 monthly intervals.
Methods: We did a retrospective notes review on 75 consecutive patients prescribed amiodarone from April 2008, and followed up the thyroid function tests done on these patients, as well as the action taken on these findings.
Results: Of a total of 75 patients, 39 were men (52%). 39 patients were over 80 years. 12 patients had previous thyroid disease, (2 hyperthyroid treated, 1 amio related and 9 hypothyroid). 52 were new prescription started as inpatients of whom 26 had baseline TFTs, and 23 were follow ups of whom 11 had TFTs done within 6 months.
Of 44 patients had no appropriate follow up testing, 31 patients had testing done appropriately and 2 patients moved out of the area.
Interestingly, 2 patients had pulmonary complications and Amiodarone had to be withdrawn and 9 patients died within 6 months of whom, 2 had TFTs within 6 months. Of all TFT reports, 13 were abnormal, with 2 patients being hyperthyroid, 2 patients significant hypothyroid and 9 had a raised TSH with normal T4. Of these 13 patients, only 6 had appropriate TFTs.
Conclusion: Thyroid function testing at regular interval is only done in about 40% of prescriptions issued. Almost 17% of those who have had regular testing did show abnormal values. Hence it is strongly advised that regular thyroid testing is encouraged in the outpatient as well as inpatient settings.