MUSTARGEN

Clinical safety rating: caution

Comprehensive clinical and safety monograph for MUSTARGEN (MUSTARGEN).

How it works

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.

What the body does with it

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.

Classification & Brands

Dosing & administration

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.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for MUSTARGEN (MUSTARGEN).

Breastfeeding	Contraindicated during breastfeeding. Mechlorethamine is excreted in breast milk (M/P ratio unknown); potential for severe neonatal immunosuppression, carcinogenesis, and growth retardation.
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.

Warnings & precautions

■ 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.

Side Effect Profile

Serious Effects

Absolute Contraindications

["Known hypersensitivity to mechlorethamine or any component of the formulation","Pre-existing severe bone marrow suppression (e.g., from prior chemotherapy or radiation)","Active infections (due to immunosuppression)","Pregnancy (teratogenic; can cause fetal harm)"]

Clinical Precautions

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."]

Clinical Tips & Counseling

Drug interactions

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MUSTARGEN

Clinical safety rating: caution

Comprehensive clinical and safety monograph for MUSTARGEN (MUSTARGEN).

How it works

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.

What the body does with it

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.

Classification & Brands

Dosing & administration

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.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for MUSTARGEN (MUSTARGEN).

Breastfeeding	Contraindicated during breastfeeding. Mechlorethamine is excreted in breast milk (M/P ratio unknown); potential for severe neonatal immunosuppression, carcinogenesis, and growth retardation.
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.