In vivo response of mitoxantrone and doxorubicin with dipyrone in parental and doxorubicin-resistant P388 leukemia.

The efficacy of dipyrone to modulate antitumor activity of mitoxantrone (MTN) and doxorubicin (DOX) was studied in vivo in mice bearing P388 murine lymphocytic leukemia sensitive (P388/S) and resistant P388/DOX) to DOX. P388/DOX-bearing mice demonstrated marginally higher sensitivity to dipyrone at 200 mg/kg when compared to P388/S-bearing mice. However, dipyrone could significantly enhance the antitumor activity of MTN and DOX in both P388/S and P388/DOX-tumor-bearing mice. MTN was cross-resistant to P388/DOX.