It is not known the safety and efficacy of Filgrastim given simultaneously with cytotoxic myelosuppressive chemotherapy. Do not use Filgrastim in the period 24 hours before through 24 hours after the administration of cytotoxic chemotherapy. Drug interactions between Filgrastim and other drugs have not been fully evaluated. Drugs which may potentiate the release of neutrophils, such as lithium, should be used with caution.