PHARMACOKINETIC STUDIES OF THE INTERACTION OF TOPOTECAN WITH CONCOMITANTLY ADMINISTERED MEDICATIONS HAVE NOT BEEN FORMALLY INVESTIGATED. IN VITRO INHIBITION STUDIES USING MARKER SUBSTRATES KNOWN TO BE METABOLIZED BY HUMAN P450 CYP1A2, CYP2A6, CYP2C8/9, CYP2C19, CYP2D6, CYP2E, CYP3A, OR CYP4A OR DIHYDROPYRIMIDINE DEHYDROGENASE INDICATE THAT THE ACTIVITIES OF THESE ENZYMES WERE NOT ALTERED BY TOPOTECAN.
CONCOMITANT ADMINISTRATION OF G-CSF (COLONY STIMULATING FACTORS LIKE FILGRASTIM) CAN PROLONG THE DURATION OF NEUTROPENIA, SO IF G-CSF IS TO BE USED, IT SHOULD NOT BE INITIATED UNTIL DAY 6 OF THE COURSE OF THERAPY, 24 HOURS AFTER COMPLETION OF TREATMENT WITH TOPOTECAN.
MYELOSUPPRESSION WAS MORE SEVERE WHEN TOPOTECAN WAS GIVEN IN COMBINATION WITH CISPLATIN.