Improved LC assay for the determination of mitozantrone in plasma: analytical considerations.
Preliminary method development studies on mitozantrone (MTZ) revealed a number of characteristics which were found to be important in the analysis of patient samples for pharmacokinetic studies. MTZ rapidly bound to glass, particularly at low concentrations (< 10 ng ml-1), necessitating the use of silanized glassware or polypropylene tubes for the handling of all solutions containing MTZ. MTZ was also found to react with two commonly-used antioxidants; sodium metabisulphite and EDTA. However, solutions containing MTZ were found to be stabilized by the addition of ascorbic acid (0.5% w/v). In the absence of ascorbic acid, MTZ underwent rapid, biphasic degradation in plasma at 24 and 37 degrees C, with terminal half-lives of approximately 70 h. Ascorbic acid (0.5% 2/v) was found to stabilize plasma samples containing MTZ throughout work-up procedures and during frozen storage. The addition of ascorbic acid to the sample collection vial was also necessary to prevent MTZ degradation in the eluting solvent of the solid-phase extraction system. Another important consideration was the requirement for an equilibration period of > 5 min after the addition of ametantrone (AM) internal standard to plasma samples. This was essential, since the slope of the calibration plot obtained using non-equilibrated plasma was approximately 30% of that obtained for calibration plots using equilibrated plasma, and would result in erroneous determination of MTZ plasma concentrations. The fully developed assay was rapid, precise and sensitive (relative errors at 1 ng ml-1 = 2.3%). MTZ concentrations determined using the LC method described in this report correlated well with an independently developed ELISA technique (r = 0.995, n = 20).
Priston
M J
MJ
FORCE Cancer Research Centre, University of Exeter, UK.
Sewell
G J
GJ
D000970:Antineoplastic Agents / Q000378:metabolism; D000975:Antioxidants / Q000378:metabolism; D001798:Blood Proteins / Q000378:metabolism; D002853:Chromatography, Liquid / Q000379:methods*; D004347:Drug Interactions; D004355:Drug Stability; D004797:Enzyme-Linked Immunosorbent Assay; D006207:Half-Life; D006493:Heparin / Q000378:metabolism; D006801:Humans; D008942:Mitoxantrone / Q000031:analogs & derivatives / Q000097:blood* / Q000378:metabolism / Q000493:pharmacokinetics; D012015:Reference Standards
D000970:Antineoplastic Agents; D000975:Antioxidants; D001798:Blood Proteins; D006493:Heparin; D008942:Mitoxantrone; C020182:ametantrone