Simultaneous quantification of vincristine and its major M1 metabolite from dried blood spot samples of Kenyan pediatric cancer patients by UPLC-MS/MS.

Vincristine (VCR) is an integral part of chemotherapy regimens in the US and in developing countries. There is a paucity of information about its disposition and optimal therapeutic dosing. VCR is preferentially metabolized to its major M1 metabolite by the polymorphic CYP3A5 enzyme, which may be clinically significant as CYP3A5 expression varies across populations.