Analysis index

1 ml serum, blood collection 8 – 12 hours after last dose

Therapeutic drug monitoring

Amiodarone:

0,5 mg/l – 2,0 mg/l,

toxic: > 2,5 mg/l

Desethylamiodarone:

1,0 mg/l – 5,0 mg/l,

toxic: > 5,0 mg/l

Amiodarone/Desethylamiodarone quotient:

1,4 - 3,3

Amiodarone works via blockage of calcium channels and is widely spread into the tissue after application. Due to differing affinity of the various tissue compartments, no uniform elimination half-life can be given; it rather rises in a steady state from approximately 24 , +/- 20 hours after initial dose for up to approximately 20 and more days. The main metabolite desethylamiodarone also has an antiarrhythmic effect. The ratio of serum concentration between amiodarone and desethylamiodarone is relatively constant initially, depending on dosage, and drops during long-term treatment in favor of metabolite-concentration (approximately 60 %). The stated therapeutic range is for the commonly used maintenance dose of approximately 200 mg/24 hours – 400 mg/24 hours. Side effects occur at amiodarone levels of > ,5 µg/ml, and at desethylamiodarone (active metabolite of amiodarone) levels > 3,9 µg/ml.

Toxicity: Neuromuscular weakness, tremor, pulmonary fibrosis, thyroid function disorders. Amiodarone inhibits the conversion of T4 to T3. Prior to therapy, a check of transaminases, AP, cholesterol, triglycerides, creatinine, TSH, FT3, FT4 and urine status is recommended. During therapy, TSH, FT3 and FT4 should be monitored.