Monitoring amiodarone's toxicities: recommendations, evidence, and clinical practice

We sought to develop an explicit evidence-based model of medication monitoring and to evaluate monitoring practices and adverse drug events in patients taking amiodarone at one institution.

We searched MEDLINE (1966 through 2000) for English-language publications providing specific monitoring recommendations for amiodarone. A cross-sectional retrospective chart review of 99 outpatients receiving amiodarone therapy between Jan 1, 2000, and Jan 1, 2001, at a large tertiary-care hospital was performed to assess monitoring practices. Adverse drug events were identified by use of structured implicit reviews. The main outcome measure was the proportion of patients receiving the monitoring recommended in the literature and having amiodarone-related adverse drug events.

Forty-three articles were identified that provided specific monitoring recommendations, although no studies were found that compared the outcomes of patients managed with different monitoring regimens. Overall, 70% of the recommended monitoring criteria were satisfied, although only 9 patients (9%; 95% confidence interval [95% CI], 3%-15%) received all of the recommended monitoring. Variability in monitoring practices was identified at all stages of the monitoring model. Of the patients, 52 (52%; 95% CI, 42%-62%) received minimum baseline evaluations, 22 (22%; 95% CI, 14%-31%) underwent ongoing surveillance, 75 (75%; 95% CI, 61%-89%) had appropriate responses to abnormal surveillance results, and 71 (71%; 95% CI, 62%-80%) had timely follow-up visits. Of the patients, 8 (8%; 95% CI, 3%-13%) had 9 amiodarone-related adverse drug events, of which 3 were judged to be preventable. Interrater agreement for monitoring processes (kappa = 0.83) and adverse drug events (kappa = 0.67) was good.

Current standards for amiodarone toxicity monitoring are based on expert opinion with limited evidence to support most recommendations. Monitoring practices appear to vary significantly, with few patients receiving all of the recommended monitoring. Some amiodarone-related adverse drug events may be preventable and patient safety might be improved with a better understanding of monitoring processes.