Mechlorethamine (topical) — Drug Monograph

Brand names: Valchlor

Drug class: Alkylating Agent

Mechanism of Action

Mechlorethamine, also known as nitrogen mustard, is a bifunctional alkylating agent. When applied topically, it undergoes rapid chemical transformation to form a reactive ethylenimine intermediate. This intermediate binds to the N7 position of guanine in DNA, leading to interstrand cross-linking and inhibiting DNA replication and transcription. In the context of mycosis fungoides, it is thought to target malignant T-cells within the skin, inducing apoptosis.

FDA Indications

• Topical treatment of Stage IA and IB mycosis fungoides-type cutaneous T-cell lymphoma in patients who have received prior skin-directed therapy

Common Side Effects

• Dermatitis
• Pruritus
• Skin ulceration
• Skin hyperpigmentation
• Skin irritation

Clinical Pearl

Valchlor represents a specialized topical formulation of a traditional systemic chemotherapy agent, specifically stabilized for skin application. Unlike systemic mechlorethamine, it does not typically cause myelosuppression, but skin reactions are nearly universal and can be dose-limiting. If severe dermatitis occurs, treatment should be suspended and then resumed at a reduced frequency (e.g., every other day) once the reaction resolves. Caregivers applying the gel must wear disposable nitrile…

Related Therapies & Mechanisms

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