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Methoxsalen (Topical)

Pronunciation

(meth OKS a len)

Index Terms

  • Methoxypsoralen

Dosage Forms

Excipient information presented when available (limited, particularly for generics); consult specific product labeling. [DSC] = Discontinued product

Lotion, External:

Oxsoralen: 1% (29.57 mL [DSC])

Brand Names: U.S.

  • Oxsoralen [DSC]

Pharmacologic Category

  • Psoralen

Pharmacology

Bonds covalently to pyrimidine bases in DNA, inhibits the synthesis of DNA, and suppresses cell division. The augmented sunburn reaction involves excitation of the methoxsalen molecule by radiation in the long-wave ultraviolet light (UVA), resulting in transference of energy to the methoxsalen molecule producing an excited state (“triplet electronic state”). The molecule, in this “triplet state,” then reacts with cutaneous DNA. Causes photosensitization which leads to cell inquiry and an inflammatory reaction. The erythematous reaction is followed over days to weeks by repair which manifests as higher melanization of the epidermis and thickening with the stratum corneum. Frequency is regulated by the erythema by healthcare provider response.

Use: Labeled Indications

Repigmentation of idiopathic vitiligo

Contraindications

Hypersensitivity to methoxsalen (psoralens) or any component of the formulation; diseases associated with photosensitivity (eg, albinism, lupus erythematosus, porphyria [cutanea tarda, erythropoietic and variegate], xeroderma pigmentosum); invasive skin cancer; melanoma or history of melanoma; children <12 years of age

Dosing: Adult

Note: Refer to treatment protocols for UVA exposure guidelines.

Vitiligo: Topical: Lotion is applied by healthcare provider prior to UVA light exposure, usually no more than once weekly; frequency is determined by erythema response

Dosing: Geriatric

Refer to adult dosing.

Dosing: Pediatric

Vitiligo: Topical: Children ≥12 years: Refer to adult dosing.

Administration

Hands and fingers of person applying the lotion should be protected to prevent possible photosensitization and/or burns.

Drug Interactions

There are no known significant interactions.

Adverse Reactions

Frequency not defined.

Dermatologic: Burning sensation of skin, erythema, skin blister, skin irritation

Warnings/Precautions

Concerns related to adverse effects:

• Burns: Serious burns may occur from ultraviolet radiation or sunlight (even if exposed through glass) if recommended exposure schedule is exceeded and/or protective clothing/sunscreen is not used

• Cataracts: Methoxsalen concentrates in the lens; eyes should be shielded from direct and indirect sunlight for 24 hours to prevent possible formation of cataracts. The risk associated with topical therapy is likely to be lower due to reduced systemic exposure to methoxsalen.

• Photosensitivity: Avoid sun (including sun lamp) exposure for 8 hours after methoxsalen exposure. Protective clothing, eyewear, and sunscreen (do not apply sunscreen to psoriatic areas) should be used for several days after combined methoxsalen/UVA therapy. Do not use in sunburned patients until they have fully recovered; pre-existing sunburn may obscure evaluation of response; advise patients to avoid sunbathing for 24 hours prior to treatment and for several days after treatment. Use extreme caution in patients who have significant exposure to the sun through their occupations.

• Skin cancer: Systemic therapy increases risk of skin cancer (basal cell, melanoma and squamous cell); has not been reported with topical treatment; use caution with fair skin or prior exposure to coal tar/UV treatment, ionizing radiation, or arsenic.

Disease-related concerns:

• Basal cell carcinoma: Use with caution in patients with multiple basal cell carcinomas or a history of basal cell carcinoma; observe closely.

Concurrent drug therapy issues:

• Photosensitizing agents: Use caution with other (systemic or topical) photosensitizing drugs (eg, thiazides, tetracyclines, fluoroquinolones, phenothiazines, sulfonamides, anthralin, coal tar preparations).

Special populations:

• Pediatric: Use is contraindicated in children <12 years of age; safety and efficacy have not been established. The long-term effects of treatment (including potential cataract formation, skin cancer development, and premature skin aging) are unknown in children.

Other warnings/precautions:

• Experienced physician: Should be administered under the supervision of an experienced physician with special competence in the diagnosis and treatment of dermatologic diseases. Product should not be dispensed to the patient.

Pregnancy Risk Factor

C

Pregnancy Considerations

Reproduction studies have not been conducted with topical methoxsalen. The extent of absorption is not known. Avoid use in pregnant women.

Patient Education

• Discuss specific use of drug and side effects with patient as it relates to treatment. (HCAHPS: During this hospital stay, were you given any medicine that you had not taken before? Before giving you any new medicine, how often did hospital staff tell you what the medicine was for? How often did hospital staff describe possible side effects in a way you could understand?)

• Patient may experience itching. Have patient report immediately to prescriber severe skin irritation, sunburn, or skin sores (HCAHPS).

• Educate patient about signs of a significant reaction (eg, wheezing; chest tightness; fever; itching; bad cough; blue skin color; seizures; or swelling of face, lips, tongue, or throat). Note: This is not a comprehensive list of all side effects. Patient should consult prescriber for additional questions.

Intended Use and Disclaimer: Should not be printed and given to patients. This information is intended to serve as a concise initial reference for healthcare professionals to use when discussing medications with a patient. You must ultimately rely on your own discretion, experience and judgment in diagnosing, treating and advising patients.

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