VALCHLOR
Clinical safety rating: caution
Comprehensive clinical and safety monograph for VALCHLOR (VALCHLOR).
Valchlor (mechlorethamine) is a nitrogen mustard alkylating agent that forms cross-links between DNA strands, leading to inhibition of DNA replication and transcription, and inducing apoptosis in rapidly dividing cells.
| Metabolism | Mechlorethamine is rapidly and extensively metabolized via hydrolysis and N-demethylation; the specific enzymes involved are not well characterized, but metabolism is non-enzymatic in aqueous solutions. |
| Excretion | Following topical application, VALCHLOR (mechlorethamine) is systemically absorbed; approximately <10% is excreted unchanged in urine. The majority of the dose is eliminated via metabolism and biliary/fecal routes, with ~50% of a systemic dose recovered in feces as metabolites. |
| Half-life | The terminal elimination half-life is approximately 24 hours after topical application, supporting daily dosing. Systemic half-life may be prolonged in patients with hepatic impairment. |
| Protein binding | Mechlorethamine is <5% bound to plasma proteins (albumin). |
| Volume of Distribution | Volume of distribution after topical application is not reported; after intravenous administration (research context), Vd is approximately 0.5–1.2 L/kg, suggestive of extensive tissue distribution. |
| Bioavailability | Topical: Systemic bioavailability ranges from <5% to 15% after application to intact skin; higher with skin barrier disruption or large surface area application. |
| Onset of Action | Topical: Clinical improvement (reduction in lesion severity) may be observed as early as 2–4 weeks of daily application; full effect may take up to 12 weeks. |
| Duration of Action | Duration of action after topical application is not well-defined; continued daily application is required to maintain disease control. Remission durations vary widely, from months to years, depending on disease severity and treatment adherence. |
Topical: Apply 0.016% mechlorethamine gel to affected areas once daily.
| Dosage form | GEL |
| Renal impairment | No dose adjustment required for renal impairment; mechlorethamine is primarily metabolized in the skin and not significantly renally excreted. |
| Liver impairment | No specific guidelines; caution advised in severe hepatic impairment as safety not established. |
| Pediatric use | Safety and efficacy in pediatric patients not established; no standard dosing recommendations. |
| Geriatric use | No specific dose adjustment; clinical studies included elderly patients with no overall differences in safety or efficacy. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for VALCHLOR (VALCHLOR).
| Breastfeeding | No data on mechlorethamine excretion in human milk. M/P ratio unknown. Due to potential for severe adverse reactions (myelosuppression, carcinogenesis) in the nursing infant, breastfeeding is contraindicated during therapy and for at least 1 week after last dose. |
| Teratogenic Risk | Valchlor (mechlorethamine) is contraindicated in pregnancy. It is an alkylating agent with known teratogenic effects. First trimester exposure is associated with major congenital malformations (e.g., CNS, skeletal, cardiac). Second/third trimester exposure may cause fetal growth restriction, myelosuppression, or stillbirth. No adequate human studies; animal data confirm embryotoxicity and teratogenicity. |
■ FDA Black Box Warning
No FDA black box warning.
| Serious Effects |
["History of severe hypersensitivity reactions to mechlorethamine or any component of the formulation"]
| Precautions | ["Mucocutaneous reactions: Severe skin irritation, blistering, and ulceration can occur; avoid application to skin folds, genitalia, or perianal area.","Hypersensitivity reactions: Contact dermatitis and systemic allergic reactions have been reported.","Secondary malignancies: Increased risk of cutaneous and non-cutaneous malignancies, particularly with prolonged use.","Embryo-fetal toxicity: Can cause fetal harm; advise women of reproductive potential to use effective contraception.","Radiation sensitization: Increased skin toxicity when used with radiotherapy."] |
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| Fetal Monitoring | Monitor complete blood counts (CBC) for myelosuppression in mother. Serial growth ultrasounds and fetal surveillance for growth restriction if inadvertent exposure occurs. Assess for fetal anomalies via high-resolution ultrasound if first trimester exposure. Monitor liver and renal function per prescribing information. |
| Fertility Effects | Mechlorethamine may impair fertility in both males and females. In males, azoospermia or oligospermia; in females, amenorrhea, premature ovarian failure, or reduced ovarian reserve due to gonadotoxic effects. Reversibility uncertain. Pre-treatment fertility preservation counseling advised. |