Methoxsalen
Other dermatological medicines
Other dermatological medicines
A psoralen that makes skin sensitive to ultraviolet A light; with UVA (PUVA) it treats severe psoriasis and vitiligo, and it is used in photopheresis.
Also called: 8-methoxypsoralen
Quick facts
- Group
- Other dermatological medicines
- Target
- DNA of skin cells, after activation by ultraviolet A light
- Used for
- Severe · Vitiligo · Cutaneous T-cell lymphoma
- Key effects
- Nausea · Itching · Expected redness after treatment
- Monitor
- Skin redness · Eye examinations for cataracts
- ATC
- D05BA02
No doses: the clinician sets them by the current guideline.
Mechanism of action
Methoxsalen is a psoralen, a plant-derived furocoumarin. It slips between DNA bases, and when long-wave ultraviolet A light reaches the skin it forms covalent bonds and crosslinks with DNA and generates reactive oxygen species. This slows the overgrowth of psoriatic skin cells, suppresses skin immune cells and stimulates melanocytes.
- Methoxsalen enters skin cells and slips into DNA
- UVA light activates it
- It crosslinks DNA and forms reactive oxygen species
- Cell overgrowth slows; melanocytes are stimulated
Indications
- Severe, disabling psoriasis not controlled by other treatments (PUVA) Psoriasis →
- Vitiligo (PUVA) Vitiligo →
- Cutaneous T-cell lymphoma (extracorporeal photopheresis) Mycosis fungoides and Sézary syndrome (cutaneous T-cell lymphoma) →
Adverse effects
Common
- Nausea
- Itching
- Expected redness after treatment; burns if overexposed
- Dizziness, headache, nervousness, insomnia
Contraindications
- Idiosyncratic reaction to psoralens
- Light-sensitive diseases (lupus, porphyrias, xeroderma pigmentosum, albinism)
- Melanoma or a history of melanoma; invasive squamous cell carcinoma
- Aphakia (no lens in the eye)
Key interactions
- Other photosensitising drugs (tetracyclines, fluoroquinolones, thiazides, sulfonamides, phenothiazines, griseofulvin, coal tar)
- Greater risk of severe burns.
What is monitored
- Skin redness and burns after each session
- Eye examinations for cataracts
- Lifelong skin checks for cancer, including melanoma
- Liver function where impaired
Administration and safety
- Given only by clinicians trained in photochemotherapy, under close supervision.
- Oral formulations differ in absorption and onset, so one is not swapped for another without the team.
- Total UVA-blocking goggles during treatment and wrap-around UVA-absorbing sunglasses for 24 hours afterwards.
Pregnancy and breastfeeding
Animal reproduction studies have not been done and fetal risk is unknown; it is used in pregnancy only if clearly needed.
Nursing care
- Review the medicine list for other photosensitising drugs before each course.
- Confirm eye protection during and after each session.
- Inspect the skin for burns and teach to report blistering or severe redness.
- Remind about lifelong skin cancer checks.
Pharmacokinetics
- Absorption
- Oral; absorption and onset differ between formulations, and fatty food slows absorption
- Metabolism
- Liver, with a large first-pass effect
- Half-life
- About one hour, but the skin stays sensitive to light for many hours
Test yourself
Think of the answer, then tap the question to see it.
What does methoxsalen need to work?
Ultraviolet A light (PUVA): the light activates it to crosslink DNA.
Why must patients wear UVA-blocking eye protection after methoxsalen?
To prevent cataracts.
Which long-term skin risks follow repeated PUVA?
Squamous cell carcinoma, melanoma and premature skin aging.
Connections
← Back to the class: Other dermatological medicines
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: DailyMed - METHOXSALEN capsule, liquid filled (DailyMed (U.S. National Library of Medicine), 2026); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
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Representative model, for educational purposes only.