Mechlorethamine

  • Alkylating agent (others: melphalan, cyclophosphamide, chlorambucil, etc.)
  • Spontaneous degradation without enzyme to create electrophiles that gives alkyl group to DNA
  • Pregnancy Category D

  • Topical

  • 10mg nitrogen mustard vials discontinued since 2018
  • Compound as aqueous solution or with ointment, typically 10 to 40 mg/dl (0.01–0.04% w/w)
  • Gel formulation also (0.016%)

  • Donates alkyl group to (alkylates) DNA leading to disruption of cell function & cell death 
  • Unclear ultimate cause of cell death (apoptosis most likely)
  • Preferentially cytotoxic to rapidly mitotic cells

  • FDA approved for Stage IA/IB:
  • T1 (limited plaques/patches mycosis fungoides, < 10% body surface area) 
  • T2 (generalized plaques/patches, > 10% body surface area) mycosis fungoides
  • Typically applied once daily until clearance: ointment 10–12 months; solution 1–4 months; 6-12 months gel
  • Systemic formulations used in Hodgkin lymphoma, chronic lymphocytic leukemia, polycythemia vera, lymphoproliferative & bronchogenic carcinoma

  • Pregnancy & lactation
  • Allergy
  • Precaution if history of multiple Squamous Cell carcinoma

  • Irritant contact dermatitis (most common)
  • Allergic contact dermatitis (aqueous > ointment)
  • Squamous Cell carcinoma (SCC) (Increased risk if combined with other treatment that increase risk of SCC, also with prolonged use of nitrogen mustard)
  • Type 1 hypersensitivity (rare)
  • Dyspigmentation (improves with time)
  • Xerosis
  • No systemic absorption

* For further reading refer to a pharmacology source

  • Do small test area for 7-10 days
  • Do not apply to face or genitalia.  In skin folds use less frequently or thin layer.
  • Use daily until clearance then use maintenance treatment for up to 9 months (but risk of relapse even with maintenance treatment)
  • If contact dermatitis: decrease frequency / strength of topical nitrogen mustard; add topical corticosteroids
  • If severe contact dermatitis, can undergo formal desensitization, or briefly hold medication, add topical corticosteroids and restarted at lower concentration