Myelotoxicity of paclitaxel (mitotax)

: Paclitaxel (single intravenous injection in a maximum tolerated dose of 4.6 mg/kg) to white outbred rats causes bone marrow hypoplasia, increased granulocyte and erythroid cell mitosis (metaphase-anaphase transition), and moderate pancytopenia developments in peripheral blood (hypoplastic anemia, deep, short-term neutropenia, lymphopenia and thrombocytopenia) in the first hours after injection. A considerable increase of polyploidy (4n) cells and a moderate increase in the structural changes (chromatid deletions) of chromosomes was observed on bone marrow metaphase plates in 24 h. The drug introduction causes earlier increase in the rate of thymus cells mitosis, a growth in the number of thymocytes with apoptosis signs, and a moderate decrease in the thymus and spleen weight. All changes are reversible. Long-term (90 days after injection) observation revealed decreased lymphocyte count in the peripheral blood and bone marrow and earlier thymus involution.