MUSTARGEN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for MUSTARGEN (MUSTARGEN).
MUSTARGEN (mechlorethamine HCl) is a nitrogen mustard alkylating agent that forms cross-links between DNA strands, inhibiting DNA replication and transcription, leading to cell death.
| Metabolism | MUSTARGEN undergoes rapid spontaneous degradation in body fluids (hydrolysis) and is metabolized via multiple pathways, including conjugation with glutathione and other thiols; no specific hepatic cytochrome P450 enzymes are involved. |
| Excretion | Renal: 50% as unchanged drug and metabolites; fecal: minor (<10%); biliary: minimal. |
| Half-life | Terminal half-life: 30-60 minutes (rapidly inactivated); clinical context: very short due to rapid hydrolysis and alkylation, necessitating rapid administration after reconstitution. |
| Protein binding | Approximately 75% bound to albumin and other plasma proteins; binding is reversible but extensive. |
| Volume of Distribution | Vd approximately 0.4-0.6 L/kg; reflects distribution primarily in extracellular fluid with rapid cellular uptake. |
| Bioavailability | IV: 100%; oral: not available; topical: minimal systemic absorption (<10%) but local effects are therapeutic. |
| Onset of Action | IV: Within minutes (alkylation of DNA begins rapidly); topical: variable, local effects within hours. |
| Duration of Action | IV: Myelosuppression peaks at 7-14 days, recovery by 21-28 days; clinical notes: effects on rapidly dividing cells persist due to DNA crosslinking. |
| Molecular Weight | 156 |
IV: 0.4 mg/kg or 12 mg/m² BSA as a single dose or divided into 0.1 mg/kg/day for 4 days.
| Dosage form | INJECTABLE |
| Renal impairment | No specific dose adjustment guidelines available; use with caution in severe renal impairment (CrCl <10 mL/min). |
| Liver impairment | Contraindicated in severe hepatic impairment (Child-Pugh class C). In mild to moderate impairment, reduce dose by 50%. |
| Pediatric use | IV: 0.4 mg/kg or 12 mg/m² BSA as a single dose; adjust based on BSA for children. |
| Geriatric use | No specific dose adjustment; monitor for increased myelosuppression due to age-related renal function decline. |
| 1st trimester | Mustargen (mechlorethamine) is contraindicated in the first trimester due to its teratogenic potential, as it is a known alkylating agent that can cause fetal malformations and spontaneous abortion. |
| 2nd trimester | Use in the second trimester should be avoided unless absolutely necessary, as there is a risk of fetal harm including growth restriction and organ toxicity. |
| 3rd trimester | Use in the third trimester carries risks of neonatal toxicity, including bone marrow suppression and potential carcinogenesis; avoid if possible. |
Clinical note
Comprehensive clinical and safety monograph for MUSTARGEN (MUSTARGEN).
| Placental transfer | Mechlorethamine has been shown to cross the placenta in animal studies, and human data are not available but likely similar. Its molecular weight (156.0 Da) and lack of strong plasma protein binding suggest significant placental transfer. |
| Breastfeeding | Mechlorethamine is excreted in breast milk. Due to the potential for serious adverse effects in nursing infants, such as immune suppression and carcinogenesis, breastfeeding is not recommended during treatment and for at least 1 week after the last dose. |
■ FDA Black Box Warning
WARNING: MUSTARGEN is a highly toxic drug. It is recommended that the drug be administered only by physicians experienced in the use of cancer chemotherapeutic agents. Severe local reactions may occur if extravasation occurs. For intravenous administration only. Do not give intramuscularly or subcutaneously.
| Serious Effects |
Hypersensitivity to mechlorethamine or any component of the formulationPregnancy (especially first trimester)Myelosuppression (e.g., severe neutropenia, thrombocytopenia)Active infectious disease (particularly varicella-zoster)
| Precautions | Bone marrow suppression (leukopenia, thrombocytopenia, anemia) is dose-limiting and may be severe; monitor blood counts closely., Extravasation causes severe tissue necrosis; ensure proper IV administration., Increased risk of secondary malignancies (e.g., acute leukemia) with long-term use., May cause severe nausea and vomiting; premedicate with antiemetics., Immunosuppression increases risk of infections., Hepatotoxicity and nephrotoxicity may occur; monitor liver and renal function. |
| Food/Dietary |
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| Lactation Rating | L5 |
| Teratogenic Risk | Pregnancy Category D. First trimester: high risk of major congenital malformations (neural tube defects, skeletal anomalies, cleft palate) due to alkylation and DNA crosslinking. Second/third trimesters: increased risk of intrauterine growth restriction, fetal death, and neonatal myelosuppression. |
| Fetal Monitoring | Baseline and serial complete blood counts (CBC) with differential. Fetal ultrasound for anomalies and growth assessment. Monitor for signs of infection and bleeding. Assess liver and renal function due to potential toxicity. |
| Fertility Effects | Causes dose-dependent gonadal suppression. In males: oligospermia, azoospermia, and permanent infertility. In females: ovarian failure, premature menopause, and reduced fertility with potential for reversible amenorrhea. |
| No specific food interactions known. Maintain adequate hydration to help prevent hyperuricemia. Avoid grapefruit and grapefruit juice due to potential CYP450 interaction (though not major, general caution advised). |
| Clinical Pearls | MUSTARGEN (mechlorethamine HCl) is a nitrogen mustard alkylating agent used in chemotherapy. Administer intravenously, avoiding extravasation (severe tissue necrosis). Pre-medicate with antiemetics. Monitor CBC for myelosuppression, especially nadir at 4-7 days. Use with caution in patients with varicella, herpes zoster, or gout/hyperuricemia. Contraindicated in pregnancy (teratogenic). |
| Patient Advice | This drug can cause severe nausea and vomiting; take anti-nausea medications as prescribed. · Report any pain, redness, or swelling at the injection site immediately. · Avoid live vaccines during treatment and for 6 months after. · Use effective contraception; do not breastfeed while on this drug. · Your blood counts will be monitored regularly; report signs of infection (fever, chills) or unusual bleeding/bruising. |