Introduction Amiodarone is associated with significant adverse drug reactions (ADRs) and guidelines recommend continued monitoring for ADRs during long-term use. However data of compliance with monitoring guidelines is lacking. The aim of this study was to assess the monitoring of liver and thyroid function on long-term amiodarone over 22-years in Tayside and secondly, to determine the incidence of abnormal biochemical results in relation to total exposure of amiodarone.
Methods Uutilizing the well-established record linkage database and the prescription-record linkage database available in Tayside, all patients who were prescribed amiodarone over the 22 years were identified. Long-term prescribing of amiodarone was defined as exposure greater than 6 months, baseline testing was defined as blood tests 6 months before or one month after commencing amiodarone and frequency of testing was performed looking at the mean number of days between testing. The test with closest temporal proximity to the commencement of amiodarone was used to identify patients with abnormal liver or/and thyroid function. Patients with baseline biochemical liver and thyroid abnormalities were excluded from the analysis.
Results A total of 1413 patients (mean age 71 ± 11, 57% male) on regularly prescribed amiodarone for more than 6 months were included for final analysis. Only 46%, 27% and 21% of patients had liver, thyroid, and combined testing respectively in accordance with national guidance, though monitoring had significantly improved over the last 22 years (p < 0.0005). Importantly our data also shows that, despite monitoring guidance, patients on long-term amiodarone are at risk of hepatic and thyroid toxicity (9.5% and 16% of patients respectively) and are more likely to develop thyroid disease compared to the general population. There was a positive correlation between duration of amiodarone exposure and percentage of patients with an abnormal result (2.46 and 2.5 fold increase over 4 years for liver and thyroid dysfunction respectively .0005).
Discussion Risks of developing ADR on amiodarone increase with continued exposure. Our study highlights the need for awareness and continued surveillance.
- Adverse Drug Reactions (ADRs)
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