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. |
| Molecular Weight | 156.01 |
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 | Valchlor (mechlorethamine) is contraindicated in the first trimester due to high risk of fetal harm based on animal studies and its alkylating mechanism causing teratogenicity. |
| 2nd trimester | Valchlor should be avoided in the second trimester; however, if use is unavoidable, the lowest possible dose and limited area of application are recommended due to potential fetal toxicity. |
| 3rd trimester | Use in third trimester may cause neonatal myelosuppression and other toxicities; avoid unless maternal benefit outweighs fetal risk. |
Clinical note
Comprehensive clinical and safety monograph for VALCHLOR (VALCHLOR).
| Placental transfer | Mechlorethamine is a small alkylating agent; based on molecular weight and lipophilicity, placental transfer is expected. Animal studies confirm embryotoxicity and teratogenicity. |
| Breastfeeding | It is not known whether mechlorethamine is excreted in human milk, but due to its potential for serious adverse reactions in nursing infants, breastfeeding is not recommended during treatment and for a period after the last application. |
■ FDA Black Box Warning
No FDA black box warning.
| Serious Effects |
Hypersensitivity to mechlorethamine or any component of the formulationPregnancy (especially first trimester)
| 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. |
| Food/Dietary | No known food interactions with topical VALCHLOR. However, caution with grapefruit or grapefruit juice may be advised due to potential CYP3A4 involvement, though systemic absorption is minimal with topical application. Avoid applying gel immediately after eating to prevent unintentional ingestion. |
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| Lactation Rating | L5 - Contraindicated |
| 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. |
| 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. |
| Clinical Pearls | VALCHLOR (mechlorethamine gel) 0.016% is a topical nitrogen mustard used for Stage IA and IB mycosis fungoides-type cutaneous T-cell lymphoma. Apply a thin film once daily to affected lesions; avoid application to mucosal surfaces, eyes, or broken skin. Due to risk of severe allergic and irritant contact dermatitis, consider pre-treatment with weak topical corticosteroids if irritation occurs. Protect applicator from light and store in original carton at room temperature. Cumulative cutaneous toxicity may occur with prolonged use. |
| Patient Advice | Apply a thin layer of gel only to the affected skin areas once daily, using the applicator provided. · Wash hands thoroughly before and after application; avoid contact with eyes, nose, mouth, and mucous membranes. · Do not cover the treated area with bandages or occlusive dressings unless directed by your doctor. · Store the gel in the original carton at room temperature away from light and heat; keep out of reach of children and pets. · Report any severe skin reactions (e.g., blistering, oozing, or intense itching) to your healthcare provider immediately. · Do not use other skin products (e.g., lotions, sunscreens) on the treated area without consulting your doctor. · Male and female patients should use effective contraception during treatment and for at least 6 months after the last dose. · Avoid breastfeeding while using this medication and for at least 1 week after the last application. |