Methoxsalen

Indications

Methoxsalen is used for: Psoriasis, Vitiligo, Eczema, T-Cell Lymphoma

Adult Dose

Topical Vitiligo: Adults and children 12 years of age and over Apply to the affected area of the skin 2 hr before UV exposure q3-7 days. The amount and time of UVA light for each treatment is based on skin type and response to treatment. patient may have UVA light treatments 2 to 4 times a week when first start and then less frequently as condition improves.

Child Dose

Topical Vitiligo: Children 12 years of age and over Apply to the affected area of the skin 2 hr before UV exposure q3-7 days. <12 years old: safety and efficacy not established

Renal Dose

Administration

Apply over lesions then expose to UVA immediately after application or wait up to 2 hr. Protect the area surrounding the lesion w/ a sunscreen. Wash and protect lesions from light after treatment; protection may be up to >48 hr. Treatment is usually repeated once wkly. Substantial repigmentation usually requires 6-9 mth of treatment.

Contra Indications

Hypersensitivity. Aphakia, existing or history of melanoma, invasive squamous cell carcinoma, photosensitivity diseases (e.g. porphyria, acute lupus erythematosus, xeroderma pigmentosum).

Precautions

Patient exhibiting multiple basal cell carcinoma or history of basal cell carcinoma, previous arsenic therapy, previous x-ray or grenz ray therapy; cardiac diseases or those unable to tolerate prolonged standing or exposure to heat stress; GI diseases or chronic infection. Hepatic impairment. Pregnancy and lactation. Lactation: not known whether excreted in breast milk; use caution

Pregnancy-Lactation

Pregnancy Category: C Lactation: not known whether excreted in breast milk; use caution

Interactions

Additive effects with drugs known to cause photosensitisation e.g. anthralin, coal tar or derivatives, griseofulvin, phenothiazines, nalidixic acid, sulfonamides., tetracyclines and thiazide diuretics. May increase the levels/effects of aminophylline, fluvoxamine, mexiletine, mirtazapine, ropinirole, theophylline, trifluoperazine, dexmedetomidine and ifosfamide.

Adverse Effects

Side effects of Methoxsalen : All Patients Mild-moderate erythema x 24-48 hrs 1-10% Nausea, Pruritis Frequency Not Defined Edema, Dizziness, Headache, Malaise, Depression, Hypopigmentation, Bullae formation, Rash, Herpes simplex, Uritcaria, GI disturbances, Leg cramps, Hypotension, Extension of psoriasis

Mechanism of Action

Methoxsalen increases skin reactivity to long-wavelength UV rays. It bonds covalently to DNA inhibiting DNA synthesis and cell division, which can lead to cell injury. This effect is used in photochemotherapy or PUVA and high-intensity long-wavelength UVA irradiation].