Since the major toxicity is delayed bone marrow suppression, blood counts should be monitored weekly for at least 6 weeks after a dose (see ADVERSE REACTIONS). At the recommended dosage, courses of BiCNU should not be given more frequently than every 6 weeks.
The bone marrow toxicity of BiCNU is cumulative and therefore dosage adjustment must be considered on the basis of nadir blood counts from prior dose (see “Dosage Adjustment Table” under DOSAGE AND ADMINISTRATION).
Pulmonary toxicity from BiCNU appears to be dose related. Patients receiving greater than 1400 mg/m2 cumulative dose are at significantly higher risk than those receiving less. Additionally delayed onset pulmonary fibrosis occurring up to 17 years after treatment has been reported in patients who receive BiCNU in childhood and early adolescence (see ADVERSE REACTIONS).
Long-term use of nitrosoureas has been reported to be associated with the development of secondary malignancies.
Liver and renal function tests should be monitored periodically (see ADVERSE REACTIONS).
BiCNU (carmustine for injection) may cause fetal harm when administered to a pregnant woman. BiCNU has been shown to be embryotoxic in rats and rabbits and teratogenic in rats when given in doses equivalent to the human dose. There are no adequate and well-controlled studies in pregnant women. If this drug is used during pregnancy, or if the patient becomes pregnant while taking (receiving) this drug, the patient should be apprised of the potential hazard to the fetus. Women of childbearing potential should be advised to avoid becoming pregnant.
BiCNU has been administered through an intraarterial intracarotid route; this procedure is investigational and has been associated with ocular toxicity.
In all instances where the use of BiCNU is considered for chemotherapy, the physician must evaluate the need and usefulness of the drug against the risks of toxic effects or adverse reactions. Most such adverse reactions are reversible if detected early. When such effects or reactions do occur, the drug should be reduced in dosage or discontinued and appropriate corrective measures should be taken according to the clinical judgment of the physician. Reinstitution of BiCNU therapy should be carried out with caution, and with adequate consideration of the further need for the drug and alertness as to possible recurrence of toxicity.
Due to delayed bone marrow suppression, blood counts should be monitored weekly for at least 6 weeks after a dose.
Baseline pulmonary function studies should be conducted along with frequent pulmonary function tests during treatment. Patients with a baseline below 70% of the predicted Forced Vital Capacity (FVC) or Carbon Monoxide Diffusing Capacity (DLCO) are particularly at risk.
Since BiCNU may cause liver dysfunction, it is recommended that liver function tests be monitored.
Renal function tests should also be monitored periodically.
Greater myelotoxicity (e.g., leukopenia and neutropenia) have been reported when carmustine was combined with cimetidine (see ADVERSE REACTIONS: Hematologic Toxicity).
Carcinogenesis, Mutagenesis, Impairment of Fertility
BiCNU is carcinogenic in rats and mice, producing a marked increase in tumor incidence in doses approximating those employed clinically. Nitrosourea therapy does have carcinogenic potential in humans (see ADVERSE REACTIONS). BiCNU also affects fertility in male rats at doses somewhat higher than the human dose.
Pregnancy Category D
It is not known whether this drug is excreted in human milk. Because of the potential for serious adverse events in nursing infants, nursing should be discontinued while taking BiCNU.
Safety and effectiveness in children have not been established. Delayed onset pulmonary fibrosis occurring up to 17 years after treatment has been reported in a long-term study of patients who received BiCNU in childhood and early adolescence (1–16 years). Eight out of the 17 patients (47%) who survived childhood brain tumors, including all the five patients initially treated at less than five years of age, died of pulmonary fibrosis. Therefore, the risks and benefits of BiCNU therapy must be carefully considered, due to the extremely high risk of pulmonary toxicity. (See ADVERSE REACTIONS: Pulmonary Toxicity.)
No data from clinical studies of BiCNU are available for patients 65 years of age and over to determine whether they respond differently than younger patients. Other reported clinical experience has not identified differences in responses between elderly and younger patients. In general, dose selection for an elderly patient should be cautious, usually starting at the low end of the dose range, reflecting the greater frequency of decreased hepatic, renal, or cardiac function and of concomitant disease or other drug therapy.
BiCNU and its metabolites are known to be substantially excreted by the kidney, and the risk of toxic reactions to this drug may be greater in patients with impaired renal function. Because elderly patients are more likely to have decreased renal function, care should be taken in dose selection, and renal function should be monitored.