Carmustine for Injection can cause fetal harm when administered to a pregnant woman based on the mechanism of action [ see Clinical Pharmacology (12.1) ] and findings in animals [see Data]. Limited available data with Carmustine for Injection use in pregnant women are insufficient to inform a drug-associated risk of major birth defects and miscarriage. Carmustine was embryotoxic in rats and rabbits and teratogenic in rats (thoracoabdominal closure, neural tube, and eye defects and malformations of the skeletal system of the fetus) when given in doses lower than the maximum cumulative human dose based on body surface area. Consider the benefits and risks of Carmustine for Injection for the mother and possible risks to the fetus when prescribing Carmustine for Injection to a pregnant woman.
Adverse outcomes in pregnancy occur regardless of the health of the mother or the use of medications. The estimated background risk of major birth defects and miscarriage for the indicated population is unknown. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2-4% and 15-20%, respectively.
Intraperitoneal (IP) administration of carmustine to pregnant rats 14 days prior to mating and during the period of organogenesis at cumulative doses ≥ 26 mg/kg (158 mg/ m 2), approximately 0.1 times the maximum cumulative human dose of 1400 mg/m 2 , resulted in pre-implantation loss, increased resorptions (including completely resorbed litters), and reduced the number of live births in the presence of maternal toxicity.
Carmustine administered IP to pregnant rats during the period of organogenesis at cumulative doses ≥ 4 mg/kg (24 mg/m 2), approximately 0.02 times the maximum cumulative human dose based on a mg/m 2 basis, resulted in reduced fetal weight and various malformations, which included thoracoabdominal closure defects, neural tube defects, and eye defects, including microphthalmia/anophthalmia, and skeletal anomalies in the skull, sternebra, vertebrae and ribs, and reduced skeletal ossification) in the presence of maternal toxicity. Embryo-fetal death was observed at cumulative doses ≥ 8 mg/kg (48 mg/m 2), approximately 0.03 times the maximum cumulative human dose on a mg/ m 2 basis. Intravenous (IV) administration of carmustine to rats at a cumulative dose of 50 mg/kg (300 mg/ m 2), approximately 0.2 times the maximum cumulative human dose on a mg/m 2 basis, during the last quarter of pregnancy resulted in the death of offspring within 4 months. Carmustine administered IV to rabbits during the period of organogenesis resulted in spontaneous abortions in mothers and growth defects in the fetus, mainly at cumulative doses ≥ 13 mg/kg (156 mg/ m 2), approximately 0.1 times the maximum cumulative human dose on a mg/ m 2 basis.
There is no information regarding the presence of carmustine in human milk, the effects on the breastfed infant, or the effects on milk production. Because many drugs are excreted in human milk and because of the potential for serious adverse events (e.g., carcinogenicity and myelosuppression) in nursing infants, nursing should be discontinued while taking Carmustine for Injection.
Advise female patients to avoid pregnancy during treatment with carmustine for injection because of the risk of fetal harm [see Use in Specific Populations (8.1)] .
Advise female patients of reproductive potential to use highly effective contraception during and for up to six months after completion of treatment.
Advise males with female sexual partners of reproductive potential to use effective contraception during carmustine for injection treatment and for at least three months after the final dose of carmustine for injection [ see Nonclinical Toxicology (13.1) ].
Based on nonclinical findings, male fertility may be compromised by treatment with carmustine for injection [see Nonclinical Toxicology (13.1)].
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 carmustine for injection in childhood and early adolescence (1-16 years). Eight out of the 17 patients (47%) who survived childhood brain tumors, including all the 5 patients initially treated at less than 5 years of age, died of pulmonary fibrosis. [see Adverse Reactions (6.1)].
Clinical studies of carmustine for injection did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects. Other reported clinical experience has not identified differences in responses between the 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.
Carmustine for injection 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.
The active ingredient in Carmustine for injection, USP is a nitrosourea with the chemical name 1,3-bis(2-chloroethyl)-1-nitrosourea and a molecular weight of 214.06. The drug product is supplied as sterile lyophilized pale yellow flakes or a congealed mass, and it is highly soluble in alcohol and lipids, and poorly soluble in water. Carmustine for Injection, USP is administered by intravenous infusion after reconstitution, as recommended.
The structural formula of carmustine is:
Carmustine for Injection, USP is available in 100-mg single dose vials of lyophilized material. Sterile diluent for constitution of Carmustine for Injection, USP is co-packaged with the active drug product for use in constitution of the lyophile. The diluent is supplied in a vial containing 3 mL of Dehydrated Alcohol Injection, USP.
The mechanism of action of carmustine is not fully understood. While carmustine alkylates DNA and RNA, it is not cross-resistant with other alkylators. As with other nitrosoureas, it may also inhibit several key enzymatic processes by carbamoylation of amino acids in proteins. The metabolites may contribute to antitumor activity and toxicities of carmustine.
Carmustine crosses the blood-brain barrier. Levels of radioactivity in the CSF are greater than or equal to 50% of those measured concurrently in plasma.
Following a short intravenous infusion, the reported elimination half-life ranges from 15 minutes to 75 minutes.
Carmustine may be inactivated through denitrosation reactions catalyzed by both cytosolic and microsomal enzymes, including NADPH and glutathione-S-transferase.
Approximately 60% to 70% of a total dose is excreted in the urine within 96 hours. Approximately 10% is eliminated as respiratory CO 2 .
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