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. Increased hematopoietic activity of the bone marrow in response to growth factor therapy has been associated with transient positive bone-imaging changes. This should be considered when interpreting bone-imaging results.

Filgrastim is given by subcutaneous injection or intravenous infusion. Filgrastim therapy should only be given in collaboration with an oncology center which has experience in G-CSF treatment and hematology and has the necessary diagnostic facilities.

For established cytotoxic chemotherapy: The recommended dose of Filgrastim is 0.5 MU (5 micrograms)/kg/day. The first dose of Filgrastim should not be administered less than 24 hours following cytotoxic chemotherapy. Filgrastim may be given as a daily subcutaneous injection or as a daily intravenous infusion diluted in 5% glucose solution given over 30 minutes. Daily dosing should continue until the expected neutrophil nadir is passed and the neutrophil count has recovered to the normal range. Following established chemotherapy with solid tumors, lymphomas, and lymphoid leukemia, the treatment duration is usually up to 14 days. Following induction and consolidation treatment for acute myeloid leukemia, the duration of treatment may be substantially longer (up to 38 days) depending on the type, dose, and schedule of cytotoxic chemotherapy used.

For severe chronic neutropenia (SCN):

Congenital neutropenia: The recommended starting dose is 1.2 MU (12 micrograms)/kg/day subcutaneously as a single dose or in divided doses.

Idiopathic or cyclic neutropenia: The recommended starting dose is 0.5 MU (5 micrograms)/kg/day subcutaneously as a single dose or in divided doses.

Dose adjustment: Filgrastim should be administered daily by subcutaneous injection until the neutrophil count has reached and can be maintained at more than 1.5 x 10⁹/L. When the response has been obtained, the minimal effective dose to maintain this level should be established. Long-term daily administration is required to maintain an adequate neutrophil count. After one to two weeks of therapy, the initial dose may be doubled or halved depending upon the patient’s response. Subsequently, the dose may be individually adjusted every 1 to 2 weeks to maintain the average neutrophil count between 1.5 x 10⁹/L and 10 x 10⁹/L. A faster schedule of dose escalation may be considered in patients presenting with severe infections.

Special dosage instructions: Clinical trials with Filgrastim have included a small number of elderly patients but special studies have not been performed in this group and therefore specific dosage recommendations cannot be made. Studies of Filgrastim in patients with severe impairment of renal or hepatic function demonstrate similar pharmacokinetics and pharmacodynamics to normal individuals. Dose adjustment is not required.

Filgrastim should not be administered in patients with known hypersensitivity to Filgrastim or to any of the excipients. It should not be used to increase the dose of cytotoxic chemotherapy beyond established dosage regimens. Filgrastim should not be administered to patients with severe congenital neutropenia (Kostmann's syndrome) with abnormal cytogenetics.

The most common adverse reactions include nausea, vomiting, musculoskeletal pain, bone pain, myalgia, and headache. Other reported effects include exacerbation of rheumatoid arthritis, splenic rupture, sickle cell crisis, acute respiratory distress syndrome (ARDS), and increased alkaline phosphatase.

The safety of Filgrastim has not been established in pregnant women. In pregnancy, the possible risk of Filgrastim use to the fetus must be weighed against the expected therapeutic benefit. It is not known whether Filgrastim is excreted in human milk, therefore Filgrastim is not recommended for use in nursing mothers.

Because of the potential sensitivity of rapidly dividing myeloid cells to cytotoxic chemotherapy, Filgrastim should not be administered 24 hours before to 24 hours after the administration of cytotoxic chemotherapy. Special caution should be used when treating patients with high-dose chemotherapy, because improved tumor outcome has not been demonstrated, and intensified doses of chemotherapeutic agents may lead to increased toxicities including cardiac, pulmonary, neurological, and dermatological effects. Regular monitoring of complete blood count is recommended twice per week during therapy. Monitoring of bone density may be indicated in patients with underlying osteoporotic bone disease who undergo continuous therapy with Filgrastim for more than six months.

The effects of Filgrastim overdose have not been established. Doses up to 138 micrograms/kg/day were administered to patients in bone marrow transplant studies without toxic effects. Discontinuation of Filgrastim therapy usually results in a 50% decrease in circulating neutrophils within one to two days, with a return to normal levels in one to seven days.

Filgrastim should be stored in a refrigerator at 2–8 °C. Do not freeze. Do not shake. Keep away from light.

Medicine: Keep out of reach of children.