Monitoring Amiodarone serum concentrations is particularly important when it is co – administered with other drugs that may interact. Clinician can use testing to evaluate possible Amiodarone toxicity and to assess patient compliance.
Amiodarone is an anti – arrhythmic agent (Class III) used to treat life-threatening arrhythmias; prolongs phase 3 of the cardiac action potential. It has numerous other effects however, including actions that are similar to those of anti-arrhythmic classes Ia, II, and IV. Amiodarone shows beta blocker-like and potassium channel blocker-like actions on the SA and AV nodes, increases the refractory period via sodium- and potassium-channel effects, and slows intra-cardiac conduction of the cardiac action potential, via sodium-channel effects. Amiodarone can be administered orally or intravenously for cardiac rhythm control. It is 95% protein bound in blood. Amiodarone elimination is quite prolonged, with a mean half-life of 53 days. CYP3A4 converts amiodarone to its equally active metabolite, N-desethylamiodarone (DEA), which displays very similar pharmacokinetics and serum concentrations, compared to the parent drug.
Numerous side effects have been associated with amiodarone. The most common adverse effect is disruption of thyroid function (hypo- or hyperthyroidism) due to amiodarone’s structural similarity to thyroid hormones. Neurological and gastrointestinal toxicities are concentration – dependent, whereas thyroid dysfunction, pulmonary fibrosis, and hepatotoxicity are more loosely linked to drug concentration. There is significant potential for drug interactions involving amiodarone, including several other cardioactive drugs (e.g Digoxin, Verapamil, class I antiarrhythmics [sodium channel blockers]), warfarin, statins, and CYP3A4 substrates.
Amiodarone: 0.5 – 2.0 mg/L
Blood specimen in Plain (red top) Tube.
Pre – dose sample.