Eribulin mesylate (E7389), a tubulin and microtubule inhibitor, continues to be approved to deal with metastatic cancer of the breast in a few patient populations. A liposomal formulation of E7389, E7389-LF, aims to improve the therapeutic profile of E7389. As figuring out the disposable drug concentration is vital for that assessment of effectiveness and toxicity of liposomal drug, within this study, an ultracentrifugation method along with LC-MS/MS was created to split up the disposable E7389 from liposomal and protein bound E7389. The pharmacokinetics from the free E7389 after dosing either E7389 or E7389-LF was characterised. The concentration ratio of E7389 in ultracentrifuged rodents plasma (UCM) versus E7389 in plasma following a 2mg/kg i.v. of E7389 ranged from 54.19% to 65.41%, which looked like the disposable fraction within the mouse plasma. The particular concentration ratio of E7389 in UCM versus E7389 in plasma following a 2mg/kg i.v. of E7389-LF ranged from .07% to .59%, and also the exposure, expressed as AUC, of UCM/plasma ratio was resolute to become .2%. Pharmacokinetic modeling was performed to estimate the discharge kinetics of E7389 from E7389-LF, and also the release was best explained an initial order rate constant k(rel) .078 h(-1). Sensitivity analysis shown that further reduce the release rate constant by modifying liposome formulation would result in decreased C(max) and far longer half-existence of UCM E7389, that might lead to better effectiveness minimizing toxicity.