A Highly Sensitive Determination of Lenalidomide in Human Plasma by Liquid Chromatography with Fluorescence Detection

Background: Lenalidomide (LND) is an oral immunomodulatory drug which is directly eliminated in the urine. LND has been used for the treatment of anemia associating chromosomal 5q deleted low- or intermediate-risk myelodysplastic syndromes (MDS) patients and recurrent multiple myeloma (MM) patients. If patients have renal failures, LND clearance could decline, resulting in thrombocytopenia as a side effect. To optimize LND doses for such patients, we developed a simple method analyzing LND concentrations in the plasma. Methods: The mixture of 150 µL plasma added 3-aminobenzyl alcohol (IS), saturated ammonium sulfate, sodium chloride and 3mL ethyl acetate/acetonitrile solution (95:5, v/v) was centrifuged. The supernatant solution was evaporated and the residue was dissolved in water. After the reaction with fluorescamine, the reaction mixture was injected into a HPLC. HPLC conditions: Capcell Pak C18 UG120 (150 × 4.6mm, 5 µm); mobile phase: 50mM phosphate buffer (pH4.0) /methanol / tetrahydrofurane (70:10:20, v/v); flow rate: 0.7mL/min; detection: excitation 382nm, emission 495nm. Results: The lower limits of quantifying the concentrations of LND in the plasma were 5ng/mL. The within- and between-day variations for LND were reliable (5.9 ∼ 13.4% and 5.9 ∼ 15.1%, respectively). This method was used to determine the plasma concentrations of LND in patients treated with LND therapy. Conclusions: This HPLC-based method is very simple, rapid and sensitive for plasma concentrations of LND, and may therefore be useful as a routine analysis for the therapeutic drug monitoring in LND-treated patients with renal failures.