Method for rapid separation of liposome-associated doxorubicin from free doxorubicin in plasma.

To understand and predict the efficacy and/or toxicity of liposomal drugs in vivo, it is essential to have rapid, reliable methods of separating and quantitating both the free and the liposomal forms of the drug. A method using solid-phase extraction chromatography columns was developed to separate and quantitate unencapsulated doxorubicin and liposome-associated doxorubicin in plasma following the intravenous injection of liposomal doxorubicin. The method facilitated the recovery and quantitation of free and liposomal drug. The separation and recovery of doxorubicin were linear across the entire range of possible mixtures (0 to 100%) of the two forms of the drug in plasma. Free drug and liposomal drug were readily separated for liposomal doxorubicin systems varying in size (0.1-1.0 microns) and lipid composition (egg yolk phosphatidylcholine/cholesterol and distearylphosphatidylcholine/cholesterol). The method is rapid and allows for multiple samples to be processed simultaneously.