Plasma amiodarone concentrations during intravenous infusion.

Amiodarone is a useful antiarrhythmic agent whose pharmacokinetics are incompletely characterised. In order to optimise efficacy of an antiarrhythmic drug, information regarding plasma concentrations achieved during use of the drug is necessary. We report plasma amiodarone and desethylamiodarone concentrations in eight patients following intravenous infusion at a rate of 175 mg h-1 for the first 2 h, followed by infusion at a rate of 50 mg h-1 for a further 46 h a regimen very similar to that recommended by the manufacturers. In at least three of eight patients plasma concentrations were below the suggested therapeutic range of 1.0-2.5 mg l-1 from 3 to 16 h after the infusion was started. Our data suggests that larger doses of intravenous amiodarone than those previously recommended may be necessary to obtain optimal benefit from the drug.