Does Oxsoralen Ultra (methoxsalen) cause side effects?

Oxsoralen Ultra (methoxsalen) is a naturally occurring photoactive chemical found in the seeds of the Ammi majus (Umbelliferae) plant and in the roots of Heraclem candicans. 

Oxsoralen Ultra (methoxsalen) belongs to a group of compounds known as psoralens, or furocoumarins. It is used combined with UVA (ultraviolet A) radiation as photochemotherapy for the treatment of severe, disabling psoriasis that is difficult to treat and is unresponsive to other treatments. It also is used to treat idiopathic vitiligo (leucoderma) and cutaneous (skin) manifestations of T-cell lymphoma

The exact mechanism of action of Oxsoralen Ultra is not known. Oxsoralen Ultra has several biological actions that may be responsible for its medical effects. Oxsoralen Ultra is a photosensitizer that increases the reaction of the skin to UVA. Oxsoralen Ultra also combines with DNA in skin cells. 

Upon administration, Oxsoralen Ultra reaches the skin via blood. When UVA penetrates the skin, cellular damage occurs, leading to inflammation. The damaged skin heals after several days to weeks. 

Some experts suggest that Oxsoralen Ultra improves vitiligo by stimulating melanocytes (melanin forming skin cells) to move up the hair follicle and to repopulate the epidermis

Psoriasis causes an overproduction of skin cells. Oxsoralen Ultra may benefit psoriasis by decreasing skin cell production by damaging DNA.

Common side effects of Oxsoralen Ultra include

Serious side effects of Oxsoralen Ultra include

Drug interactions of Oxsoralen Ultra include drugs that cause sun sensitivity, such as coal tar or coal tar derivatives, doxycycline, tetracycline, demeclocycline, methylene blue, griseofulvin, thiazide diuretics, fluoroquinolone antibiotics, and several other drugs, because this will increase the risk of severe skin burns when using Oxsoralen Ultra. 

Oxsoralen Ultra has not been adequately studied in pregnant women. Animal data suggest that Oxsoralen Ultra can harm the fetus when used by a pregnant woman. Women of childbearing potential should be advised to avoid becoming pregnant

It is unknown if Oxsoralen Ultra is excreted in breast milk. Consult your doctor before breastfeeding.

What are the important side effects of Oxsoralen Ultra (methoxsalen)?

Common side effects include:

Other side effects include:

Possible serious side effects include:

  • Severe burns from over exposure to UVA or sunlight
  • Blisters
  • Keratosis
  • Sun sensitivity
  • Worsening of psoriasis
  • Basal cell carcinoma
  • Premature aging

Oxsoralen Ultra (methoxsalen) side effects list for healthcare professionals


The most commonly reported side effect of methoxsalen alone is nausea, which occurs with approximately 10% of all patients. This effect may be minimized or avoided by instructing the patient to take methoxsalen in milk or food, or to divide the dose into two portions, taken approximately one-half hour apart. Other effects include nervousness, insomnia, and depression.

Combined Methoxsalen/Uva Therapy

  1. Pruritus: This adverse reaction occurs with approximately 10% of all patients. In most cases, pruritus can be alleviated with frequent application of bland emollients or other topical agents; severe pruritus may require systemic treatment. If pruritus is unresponsive to these measures, shield pruritic areas from further UVA exposure until the condition resolves. If intractable pruritus is generalized, UVA treatment should be discontinued until the pruritus disappears.
  2. Erythema: Mild, transient erythema at 24-48 hours after PUVA therapy is an expected reaction and indicates that a therapeutic interaction between methoxsalen and UVA occurred. Any area showing moderate erythema (greater than Grade 2 - See Table 1 for grades of erythema) should be shielded during subsequent UVA exposures until the erythema has resolved. Erythema greater than Grade 2 which appears within 24 hours after UVA treatment may signal a potentially severe burn. Erythema may become progressively worse over the next 24 hours, since the peak erythemal reaction characteristically occurs 48 hours or later after methoxsalen ingestion. The patient should be protected from further UVA exposures and sunlight, and should be monitored closely.
  3.  Important differences between PUVA Erythema and Sunburn: PUVA-induced inflammation differs from sunburn or UVB phototherapy in several ways. The percent transmission of UVB varies between 0% to 34% through skin whereas UVA varies between 1% to 80% transmission; thus, UVA is transmitted to a larger percent through the skin. The DNA lesions induced by PUVA are very different from UV-induced thymine dimers and may lead to a DNA crosslink. This DNA lesion may be more problematic to the cell because crosslinks are more lethal and psoralen-DNA photoproducts may be “new” or unfamiliar substrates for DNA repair enzymes. DNA synthesis is also suppressed longer after PUVA. The time course of delayed erythema is different with PUVA and may not involve the usual mediators seen in sunburn. PUVAinduced redness may be just beginning at 24 hours, when UVB erythema has already passed its peak. The erythema dose-response curve is also steeper for PUVA. Compared to equally erythemogenic doses of UVB, the histologic alterations induced by PUVA show more dermal vessel damage and longer duration of epidermal and dermal abnormalities.
  4. Other adverse reactions: Those reported include edema, dizziness, headache, malaise, depression, hypopigmentation, vesiculation and bullae formation, non-specific rash, herpes simplex, miliaria, urticaria, folliculitis, gastrointestinal disturbances, cutaneous tenderness, leg cramps, hypotension, and extension of psoriasis.

What drugs interact with Oxsoralen Ultra (methoxsalen)?

See prescribing information.

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Medically Reviewed on 9/25/2020
FDA Prescribing Information

Professional side effects and drug interactions sections courtesy of the U.S. Food and Drug Administration.