8-MOP Side Effects Center

Last updated on RxList: 1/31/2023
8-MOP Side Effects Center

What Is 8-MOP?

8-MOP (methoxsalen) is a naturally occurring substance that is reactive to light used in combination with UVA light therapy to treat severe psoriasis.

What Are Side Effects of 8-MOP?

8-MOP may cause serious side effects including:

  • hives,
  • difficulty breathing,
  • swelling of your face, lips, tongue, or throat,
  • severe skin redness within 24 hours after UVA treatment,
  • swelling,
  • severe itching,
  • severe skin discomfort,
  • skin redness and swelling with blisters,
  • worsening of your psoriasis,
  • new skin lesion,
  • moles that have changed in size or color,
  • blurred vision,
  • tunnel vision,
  • eye pain or swelling, and
  • seeing halos around lights

Get medical help right away, if you have any of the symptoms listed above.

Common side effects of 8-MOP include:

  • nausea
  • trouble sleeping (insomnia)
  • depression
  • nervousness
  • sleep problems (insomnia)
  • cold sores
  • headache
  • dizziness
  • leg pain
  • mild skin changes (itching, drying, redness, tenderness, or darkening of skin) when this drug is used along with UVA light treatment

Seek medical care or call 911 at once if you have the following serious side effects:

  • Serious eye symptoms such as sudden vision loss, blurred vision, tunnel vision, eye pain or swelling, or seeing halos around lights;
  • Serious heart symptoms such as fast, irregular, or pounding heartbeats; fluttering in your chest; shortness of breath; and sudden dizziness, lightheadedness, or passing out;
  • Severe headache, confusion, slurred speech, arm or leg weakness, trouble walking, loss of coordination, feeling unsteady, very stiff muscles, high fever, profuse sweating, or tremors.

This document does not contain all possible side effects and others may occur. Check with your physician for additional information about side effects.

Dosage for 8-MOP

Dosing of 8-MOP is based on the patient's weight. The capsules should be taken 2 hours before UVA exposure with some food or milk.

What Drugs, Substances, or Supplements Interact with 8-MOP?

8-MOP may interact with arsenic trioxide, anthralin, bacteriostatic soaps, coal tar, griseofulvin, nalidixic acid, staining dyes, sulfa drugs, diuretics (water pills), antibiotics, or medicines to treat psychiatric disorders. Tell your doctor all medications and supplements you use, including those applied to the skin.

8-MOP During Pregnancy or Breastfeeding

8-MOP is not recommended for use during pregnancy. It may harm a fetus. It is unknown if this medication passes into breast milk. Because of the possible risk to the infant, breastfeeding while using this drug is not recommended.

Additional Information

Our 8-MOP (methoxsalen) Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.


Psoriasis causes the top layer of skin cells to become inflamed and grow too quickly and flake off. See Answer
8-MOP Consumer Information

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have:

  • severe skin redness within 24 hours after UVA treatment;
  • swelling, severe itching, or severe skin discomfort;
  • skin redness and swelling with blisters;
  • worsening of your psoriasis;
  • a new skin lesion, or a mole that has changed in size or color; or
  • blurred vision, tunnel vision, eye pain or swelling, or seeing halos around lights.

Mild skin redness may occur and can last for 1 or 2 days. This is a normal side effect after UVA treatment and may not be a sign of severe sunburn. Ask your doctor if you have concerns about any redness or swelling.

Common side effects may include:

  • itching, redness;
  • nausea;
  • feeling nervous; or
  • sleep problems (insomnia).

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.


Types of Psoriasis: Medical Pictures and Treatments See Slideshow
8-MOP Professional Information



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 with milk or food, or to divide the dose into two portions, taken approximately one-half hour apart. Other effects include nervousness, insomnia, and psychological 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 in situ depth of photochemistry is deeper within the tissue because UVA is transmitted further into 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. PUVA-induced 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.

Read the entire FDA prescribing information for 8-MOP (Methoxsalen)

© 8-MOP Patient Information is supplied by Cerner Multum, Inc. and 8-MOP Consumer information is supplied by First Databank, Inc., used under license and subject to their respective copyrights.

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