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Pharmacology and Pharmacokinetics of Amiodarone
Author(s) -
Freedman Michael D.,
Somberg John C.
Publication year - 1991
Publication title -
the journal of clinical pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.92
H-Index - 116
eISSN - 1552-4604
pISSN - 0091-2700
DOI - 10.1002/j.1552-4604.1991.tb03673.x
Subject(s) - amiodarone , pharmacokinetics , pharmacology , active metabolite , antiarrhythmic agent , vasodilation , enterohepatic circulation , medicine , compartment (ship) , metabolite , inotrope , distribution (mathematics) , quinidine , flecainide , chemistry , metabolism , heart disease , mathematical analysis , oceanography , mathematics , geology , atrial fibrillation
Amiodarone is a unique antiarrhythmic agent originally developed as a vasodilator. Classified electrophysiologically as a Type III antiarrhythmic, it also has both nonspecific antisympathetic and direct, fast channel‐membrane effects. Hemodynamic effects of orally administered amiodarone (a negative inotropic agent) are usually negligible, and are usually compensated for by induced vasodilation. Effects on thyroid and hepatic function may help to explain some of the unique pharmacologic as well as toxicologic effects of the drug. Amiodarone is poorly bioavailable (20–80%) and undergoes extensive enterohepatic circulation before entry into a central compartment. The principal metabolite, mono‐n‐desethyl amiodarone is also an antiarrhythmic. From this central compartment, it undergoes extensive tissue distribution (exceptionally high tissue/plasma partition coefficients). The distribution half‐life of amiodarone out of the central compartment to peripheral and deep tissue compartments (t1/2 α ) may be as short as 4 hours. The terminal half‐life (t 1/2β ) is both long and variable (9–77 days) secondary to the slow mobilization of the lipophilic medication out of (primarily) adipocytes. A pharmacokinetically based loading scheme is described, and data suggesting a role for routine amiodarone plasma levels are presented.