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Topical alkylating agent Pregnancy: UK SPC §4.6. Women of childbearing potential: not recommended in women of childbearing potential who are not using contraception. Pregnancy: there are limited data from use in pregnant women and animal studies have shown reproductive toxicity after systemic administration — not recommended during pregnancy. Breast-feeding: it is unknown whether chlormethine is excreted in human milk; a risk to newborns/infants cannot be excluded because of potential topical or systemic exposure of the breast-fed child through contact with the mother's skin, so a decision must be made whether to discontinue breast-feeding or to discontinue therapy. Fertility: adverse effects on male fertility after systemic administration have been documented in animals; the relevance to humans receiving topical chlormethine is unknown.

Chlormethine (Specialist drug)

Brand names: Ledaga

Chlormethine (mustine) is a nitrogen mustard alkylating agent; as a topical gel it is used for mycosis fungoides-type cutaneous T-cell lymphoma.

Adult dose

Dose: Mycosis fungoides-type cutaneous T-cell lymphoma (MF-type CTCL), topical chlormethine gel 160 micrograms/g: apply a thin film once daily to affected areas of the skin
Route: Topical application to the skin. Apply to completely dry skin at least 4 hours before, or 30 minutes after, showering or washing. Allow treated areas to dry for 5 to 10 minutes after application before covering with clothing. Occlusive (air- or water-tight) dressings must not be used on treated areas.
Frequency: Once daily. Stop treatment for any grade of skin ulceration or blistering, or for moderately severe or severe dermatitis (e.g. marked skin redness with oedema). On improvement, restart at a reduced frequency of once every 3 days; if reintroduction is tolerated for at least 1 week, increase to every other day for at least 1 week, and then to once-daily application if tolerated.
Treatment should be initiated by an appropriately experienced physician. ELDERLY: the dosing recommendation for patients aged 65 years and over is the same as for younger adult patients. PAEDIATRIC: the SPC states that safety and efficacy in children aged 0 to 18 years have not been established and that no data are available, so no paediatric dose exists to publish — direct any under-18 use to a specialist and to current prescribing references. NO NUMERIC CEILING IS STATED: the SPC gives no maximum quantity per application and no maximum body area, so adultDose.maxDose has deliberately been left out rather than invented; once-daily application is the maximum frequency. HANDLING (from §4.2): patients must wash hands thoroughly with soap and water immediately after handling or applying the gel, and should wash any non-affected skin that is exposed. Caregivers must wear disposable nitrile gloves, remove them turned inside out, and wash hands thoroughly afterwards; accidental skin exposure requires immediate washing of the exposed area for at least 15 minutes and removal and washing of contaminated clothing. The tube opening carries a foil safety seal which the cap is used to puncture — do not use the tube and contact the pharmacist if the seal is missing, punctured or lifted. STORAGE: the gel is refrigerated; apply immediately or within 30 minutes of removal from the refrigerator and return the tube to the refrigerator immediately after each use, replaced in its original box inside the supplied sealable plastic bag. CONCOMITANT TOPICALS: emollients (moisturisers) or other topical products may be applied to the treated areas 2 hours before or 2 hours after application. FLAMMABILITY: fire, flame and smoking must be avoided until the gel has dried. SECONDARY EXPOSURE: direct skin contact with the gel by anyone other than the patient must be avoided — risks include skin reactions, mucosal injury and skin cancers.

Dose independently re-sourced from UK Summary of Product Characteristics (SPC) via the eMC — clinician-reviewed. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

  • Hypersensitivity to chlormethine or to any of the excipients of the gel

Side effects

  • Dermatitis — very common (54.7% in the randomised controlled trial; includes skin irritation, erythema, rash, urticaria, skin-burning sensation and pain of the skin)
  • Pruritus — very common (20.3%)
  • Skin infections — very common (11.7%)
  • Skin ulceration and blistering — common (6.3%)
  • Skin hyperpigmentation — common (5.5%)
  • Hypersensitivity — common; cutaneous hypersensitivity reactions were reported in 2.3% of treated patients, and isolated cases of anaphylaxis have been reported in the literature with topical chlormethine formulations
  • Mucosal and eye exposure (not an adverse reaction of correct use but the principal handling hazard): exposure of oral or nasal mucosa causes pain, redness and ulceration, which may be severe; eye exposure causes pain, burns, inflammation, photophobia and blurred vision, and blindness and severe irreversible anterior eye injury may occur
  • The safety profile in patients aged 65 years and over (31% of the controlled trial population) was consistent with that in the overall population

Interactions

  • No interaction studies have been performed (SPC §4.5).

Monitoring

  • Assess the skin during treatment for reactions — dermatitis (redness, swelling, inflammation), pruritus, blisters, ulceration and skin infections; the face, genitalia, anus and intertriginous skin are at increased risk. Modify the dosing frequency as set out above if these occur.
  • Monitor for the development of skin cancers during treatment and after discontinuation — skin-directed therapies for MF-type CTCL have been associated with secondary skin cancers, although the specific contribution of chlormethine has not been established.
  • If mucous membrane exposure occurs, irrigate immediately for at least 15 minutes with copious water (or sodium chloride 9 mg/ml (0.9%) solution for injection, or a balanced salt ophthalmic irrigating solution for eye exposure) and obtain medical care immediately, including ophthalmological consultation for eye exposure.

Clinical monograph

How it works

It alkylates and cross-links DNA, inhibiting DNA replication and causing death of rapidly dividing cells in the skin lesions.

Prescribing in practice

  • The topical gel commonly causes dermatitis (skin redness, irritation and inflammation), which may require dose-frequency adjustment or interruption.
  • It is for cutaneous use only; avoid contact with the eyes, mucous membranes and healthy skin, and wash hands after handling.
  • Caregivers should apply with care and avoid their own skin contact, and treated areas should not be occluded unless directed.

Monitoring

Monitor the skin for irritation, dermatitis and secondary infection during treatment.

Counselling the patient

  • Apply only to affected skin as directed and allow it to dry; wash your hands thoroughly afterwards.
  • Keep the gel away from your eyes, nose and mouth, and rinse immediately with plenty of water if accidental contact occurs.
  • Report troublesome skin redness, blistering or signs of infection to your team.

Evidence & guidelines

Topical chlormethine is an established option for early-stage cutaneous T-cell lymphoma, supported by clinical trial evidence and reflected in the SPC.

Reference: Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

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