Loading, release and stability of epirubicin-loaded drug-eluting beads.

Abstract

The aim of this study was to determine the loading efficiency, physico-chemical stability and release of epirubicin-loaded DC Bead™ (Biocompatibles UK Ltd, a BTG International group company) (bead size 70-150 µm (=DC BeadM1™) and 100-300 µm) after loading with epirubicin solution (2 mg/ml) or reconstituted powder formulation (25 mg/ml) and controlled storage. DC Bead™ were loaded with 76 mg epirubicin solution (Epimedac™, Medac GmbH) or 75 mg epirubicin powder formulation (Farmorubicin™, Pharmacia Pfizer GmbH) per 2 ml of beads. Drug loading efficiency and stability were determined by measuring the epirubicin concentration in the excess solution after predetermined intervals (maximum 24 h) and different agitation conditions.Syringes with loaded beads were stored protected from light at room temperature. At predetermined intervals the beads were transferred into 200 ml phosphate buffered solution (pH 7.2) as elution medium and stirred automatically for 2 h not followed or followed by addition of 200 ml of 20% sodium chloride (=NaCl) solution and stirred for another 2 h to analyse the drug release and integrity of the epirubicin-loaded beads. Elution experiments were performed and samples taken periodically over a four-week period (day 0, 7, 14 and 28). A reversed-phase high-performance liquid chromatography assay with ultraviolet detection was utilized to analyse the concentration and purity of epirubicin. The loading procedure for DC Bead™ with epirubicin drug solutions resulted in a loading percentage of 95-99% within 6 h dependent on the bead size, epirubicin concentration in the loading solution and loading conditions. Loading levels remained stable and no epirubicin degradation products were observed over the period of 28 days, while the loaded beads were stored light protected at room temperature.Release of epirubicin into 200 ml phosphate buffered solution elution medium and additionally followed by release into the admixture with 200 ml 20% NaCl solution amounted to 5% and about 20% of the loaded epirubicin, respectively. Integrity of loaded epirubicin was proven over 28 days. Epirubicin can be loaded into DC Bead™ of different sizes using the epirubicin powder formulation (25 mg/ml) or epirubicin injection concentrate (2 mg/ml). Physico-chemical stability is maintained over a period of at least 28 days when stored light protected at room temperature. Elution of epirubicin is dependent on the volume and cation exchange capacity of the elution medium.