Detection of bacterial endotoxin in antitumor agents

The Limulus amebocyte lysate assay was used to detect the presence of bacterial endotoxin in a variety of chemotherapeutic agents currently in use. Results were quantitated using a standard Escherichia coli endotoxin curve. Relative concentrations of endotoxin ranging from 0.1 to 63 ng/ml were detected in individual lots of L-asparaginase, 5-azacytidine, bleomycin, DTIC, actinomycin D, adriamycin, and vinblastine diluted to normal concentrations for injection. When multiple lots of a given drug were tested, at least one lot produced a negative assay, indicating less than 0.1 ng/ml of endotoxin in 50% of these drugs. All lots of cytosine arabinoside, cyclophosphamide, daunorubicin, vincristine, and streptozotocin tested had less than 0.1 ng/ml of endotoxin. Inactivation kinetics of the Limulus-positive drug material in dilute alkali solutions were identical to those of E. coli endotoxin. The Limulus lysate test is a rapid and specific method for the detection of small amounts of bacterial endotoxin contaminating parenteral preparations of antitumor agents.