Misonidazole enhances cyclophosphamide toxicity to bone marrow

Area of Science:

• Hematology
• Pharmacology
• Oncology

Background:

• Cyclophosphamide is a widely used chemotherapy agent.
• Misonidazole is an investigational hypoxic cell radiosensitizer.
• The combined toxicity of these agents on bone marrow is not well understood.

Purpose of the Study:

• To investigate the effects of misonidazole pretreatment on cyclophosphamide-induced myelosuppression.
• To assess the impact on hematopoietic stem cells and animal survival.

Main Methods:

• Animals received multiple low doses of misonidazole followed by cyclophosphamide.
• Hematological parameters (white blood cell counts, differentials, hematocrits) were monitored.
• Bone marrow colony-forming unit assays (CFUc) and survival studies were conducted.

Main Results:

• Routine hematological assays showed no significant difference between groups.
• Misonidazole pretreatment significantly reduced animal survival and delayed bone marrow CFUc recovery (p < 0.01).
• Combined treatment resulted in reduced survival, primarily due to hematopoietic failure.

Conclusions:

• Misonidazole enhances the myelotoxicity of cyclophosphamide.
• This enhanced toxicity is detectable through bone marrow stem cell assays and survival studies, not routine hematology.
• Caution is advised when considering combined use of misonidazole and cyclophosphamide.