Determination of Ethambutol n Human Plasma by a Validated HPLC Method and Its Application to Single-dose Pharmacokinetics

An HPLC method was employed for the determination of ethambutol in human plasma. After addition of internal standard (IS, octylamine, $2\;{\mu}g/mL$) and alkalinization of the plasma with 5 M sodium hydroxide, the drug and IS were extracted into the mixture of chloroform and diethyl ether (40:60, v/v). Following a 15-min vortex-mixing and a 10min centrifugation, the organic phase was spiked with $100{\mu}L$ of phenylethylisocyanate $(2000{\mu}g/mL)$ for chemical derivatization, mixed for 5 min and evaporated to dryness under a stream of nitrogen. The residue was reconstituted with $100{\mu}L$ of mobile phase and $20{\mu}L$ was injected into C18 column with a mobile phase consisting of methanol:water (70:30, v/v). The samples were detected utilizing an ultraviolet detector at 200 nm. The method was specific and validated with a limit of $0.15\;{\mu}g/mL$. Intra- and inter-day precision and accuracy were acceptable for all quality control samples including the lower limit of quantification. The applicability of this method was demonstrated by analysis of human plasma after oral administration of a single 1200-mg dose to 20 healthy subjects. From the plasma ethambutol concentration vs. time curves, the mean AUC was $9.61{\pm}1.64\;{\mu}g{\cdot}hr/mL$ and Cmax of $2.68\;{\mu}g/mL$ reached 2.73 hr after administration. The mean biological half-life of ethambutol was $3.46{\pm}1.21$ hr. Based on the results, this simple and validated assay could readily be used in any pharmacokinetic studies using humans.

인체혈장 중 에탐부톨의 HPLC 분석법의 검증 및 단일용량 투여에 의한 약물동태 연구