A sensitive method for the determination of entecavir at picogram per milliliter level in human plasma by solid phase extraction and high-pH LC-MS/MS.

Entecavir is a guanine nucleoside analogue used in the treatment of hepatitis B virus (HBV) infection. In this paper, we describe an LC-MS/MS method that was developed and validated for the quantitation of entecavir in human EDTA plasma with both high sensitivity (lower limit of quantitation (LLOQ) of 5 pg/mL) and a wide concentration range (5000-fold) intended for low dose ascending clinical studies. High enrichment was achieved by taking advantage of the excellent loading capacity and reproducibility of Oasis HLB 96-well solid phase extraction plate, which allowed 1 mL of plasma samples to be processed in two equal sequential loading steps.