High-performance liquid chromatographic analysis of the antitumour drug camptothecin and its lactone ring-opened form in rat plasma.

A sensitive high-performance liquid chromatographic (HPLC) method is described for the simultaneous determination of the antitumour drug camptothecin (I) and its lactone ring-opened form (II) in plasma. The sample pretreatment involved protein precipitation with cold methanol (-30 degrees C). The methanolic extract was injected directly onto the HPLC column. Chromatography was carried out with a LiChrosorb RP-18 column (particle size 5 microns) and a mobile phase composed of methanol-phosphate buffer (5 mM, pH 6.5)-0.3 M tetrabutylammonium phosphate solution (500:500:15, v/v/v). The column effluent was monitored spectrofluorimetrically with the excitation wavelength set at 369 nm and the emission wavelength at 426 nm. The chemical stabilities of camptothecin and the ring-opened form in aqueous solutions, in plasma and after methanolic extraction, were investigated. The proposed method was validated and utilized in pharmacokinetic studies with rats.