A sensitive reversed-phase high-performance liquid chromatographic fluorescence method is described for the simultaneous determination of topotecan (I) and the hydrolysed lactone ring-opened product hydroxy acid (II) in plasma and for the determination of I in urine. To 250 μl of plasma, a 750-μl volume of cold methanol was added to stabilize the pH-dependent conversion of I into II. In plasma, the lower limit of quantitation (LLQ) for both compounds was 0.10 ng/ml. The between-day variation for I at the LLQ was 7.1% and for II was 5.5%. Prior to injection, urine samples were acidified with orthophosphoric acid and diluted with phosphate-buffered saline (PBS). In urine, the calibration curve for I was linear in the range of 10 to 250 ng/ml and the LLQ was 10 ng/ml. The assay was developed to enable pharmacological analysis of I, in on-going phase I and II studies, in patients with solid tumors.

Topotecan
dx.doi.org/10.1016/0378-4347(95)00529-3, hdl.handle.net/1765/64345
Journal of Chromatography B: Biomedical Applications
Department of Medical Oncology

Loos, W.J, Stoter, G, Verweij, J, & Schellens, J.H.M. (1996). Sensitive high-performance liquid chromatographic fluorescence assay for the quantitation of topotecan (SKF 104864-A) and its lactone ring-opened product (hydroxy acid) in human plasma and urine. Journal of Chromatography B: Biomedical Applications, 678(2), 309–315. doi:10.1016/0378-4347(95)00529-3