Amiodarone and Desethylamiodarone
Sample: Serum or EDTA plasma (Sample collection)
Schedule: Twice a week results (HPLC UV)
Units: mg/L
Range: Therapeutic range : 1.0 to 2.5 mg/L of amiodarone Toxic effects : > 2.5 mg/L of amiodarone
Remarks: Amiodarone (Cordarone®) is a N-antiarrhythmic Class III drug capable of blocking both α- and β-adrenoreceptors, effective in controlling re-entry-type arrhythmias associated with Wolf-Parkinson-White syndrome. In therapy its potent effectiveness can lead to strong negative side effects, so regular monitoring of amiodarone serum levels is essential.
The primary metabolite of amiodarone is desethylamiodarone, a substance also with a strong active cardiac anti arrhythmic effect. Side effects: Hyper and hypothyroidism, pulmonary toxicity (pneumonitis and interstitial fibrosis of the lung), peripheral neuropathy, extra pyramidal symptoms, neuromuscular weakness, exacerbation of congestive heart failure, tremor, alterations of skin and cornea.
Drug monitoring (TDM): The usual sample time is ≥8 hours after dosing. The efficacy of amiodarone is given at serum concentrations of > 1.0 mg/L whereas desethylamiodarone concentration may account for up to 60% of amiodarone. Toxicity occurs at serum concentrations of > 2.5 mg/L of amiodarone.
This slight range of clinical use both for amiodarone and its cardiac active metabolite desethylamiodarone makes mandatory the drug monitoring of both substances before deciding the dose for each patient.
