APPLICATION OF THE EMPORE SOLID-PHASE EXTRACTION MEMBRANE TO THE ISOLATION OF DRUGS FROM BLOOD .1. AMIODARONE AND DESETHYLAMIODARONE

We describe the use of a new form of solid-phase material, the Empore solid-phase extraction membrane (SPEM), for therapeutic drug monitoring. We evaluated the new extraction procedure with the companion high-performance liquid chromatographic (HPLC) method for the antiarrhythmic drug amiodarone and its metabolite, desethylamiodarone, in patients' serum. Acidified serum (250-mu-l) was passed through an octyl (C-8) SPEM secured in an MF-1 microfilter unit. Serum proteins and potential interferences were removed with an acetonitrile:water wash, and the retained drugs eluted with HPLC mobile phase. This eluate was injected directly onto the analytical column. Both drugs averaged 85% recovery with a linear response from a lower limit of detection at 0.05 mg/L up to 6 mg/L, and between-run precision coefficients of variation ranging from 3.1 to 6.4% over the concentration range of 0.5-3.0 mg/L. We observed significant advantages of the novel SPEM over conventional liquid-liquid or large-particle size solid-phase sorbents packed in cartridges. Minimal amounts of solvents were required, elution volume was smaller, time-consuming evaporating/concentrating steps that can influence drug stability were avoided, and little throw-away material was generated. Only the small membrane was discarded.