Screening of cytotoxic drugs for residual bone marrow damage

Several cytotoxic drugs were tested for their ability to produce permanent residual damage to the bone marrow. A short course of the drug was given to BALB/c female mice, and the numbers of various types of bone marrow cells were determined at least two months later. Evidence of residual damage was found after administration of busulfan and 1,3-bis(chloroethyl)-1-nitrosourea, but not after administration of cyclophosphamide, 5-fluorouracil, 6-mercaptopurine, methotrexate, or vinblastine.