Adsorption of Mycophenolic Acid and Its Phenolic Glucuronide to Glass, Polystyrene, and Polypropylene Containers

Abstract

Drugs in solution may be adsorbed to the surface of containers and thus be removed from solution. We studied the loss of mycophenolic acid (MPA) and its major metabolite mycophenolic acid glucuronide (MPAG) from glass, polystyrene, and polypropylene containers based on solvent and time of contact. MPA was from Hoffmann-La Roche and MPAG from Analytical Services International Ltd. Acetonitrile (Uvasol; purity >99.8%), methanol (Uvasol; purity >99.8%), and orthophosphoric acid (85% Suprapur; Merck) were HPLC grade. The NaCl solution (9 g/L, pH 7.4) was from Fresenius Kabi. Stock solutions of MPA, MPAG, and MPA/MPAG were prepared in acetonitrile–water (80:20 by volume) and stored in polystyrene tubes at −80 °C. The chromatographic analysis was performed as described previously (1), with a minor gradient modification. Studies were performed on ice, which stabilizes drugs for at least 8 h (2). The MPA/MPAG stock solution was diluted with acetonitrile, methanol, or isotonic NaCl in five 6-mL glass (VSM; 69% SiO2, 13% Na2 …