Methoxsalen

Pronunciation: meth-OX-a-len
Class: Psoralen

Trade Names

8-MOP
- Capsules 10 mg

Oxsoralen
- Lotion 1% (10 mg/mL)

Oxsoralen-Ultra
- Capsules, soft gelatin 10 mg

Uvadex
- Solution, extracorporeal 20 mcg/mL

Pharmacology

Exact mechanism not known; however, methoxsalen acts as a photosensitizer.

Pharmacokinetics

Absorption

8-MOP

Max bioavailability is reached 1.5 to 3 h after oral administration and lasts up to 8 h.

Oxsoralen-Ultra

Reaches peak blood drug levels in 0.5 to 4 h, and detectable levels are observed up to 12 h.

Distribution

Methoxsalen is reversibly bound to serum albumin and preferentially taken up by epidermal cells.

Metabolism

Methoxsalen is rapidly metabolized.

Elimination

Approximately 95% is excreted as a series of metabolites in the urine within 24 h.

Oxsoralen-Ultra

The half-life is approximately 2 h.

Duration

8-MOP

Time of peak photosensitivity is 3.9 to 4.25 h.

Oxsoralen-Ultra

Time of peak photosensitivity is 1.5 to 2.1 h.

Indications and Usage

Symptomatic control of severe, recalcitrant, disabling psoriasis not responsive to other forms of therapy and when diagnosis is supported by biopsy ( Oxsoralen-Ultra , 8-MOP capsule); use in conjunction with long-wave UV radiation for repigmentation of idiopathic vitiligo ( 8-MOP capsule, Oxsoralen lotion); with long-wave UV radiation of white blood cells (photopheresis) with the UVAR photopheresis system in the palliative treatment of skin manifestations of cutaneous T-cell lymphoma in people not responsive to other forms of treatment ( 8-MOP capsule); extracorporeal administration with UVAR photopheresis system in the palliative treatment of skin manifestation of cutaneous T-cell lymphoma that is unresponsive to other forms of treatment ( Uvadex solution).

Contraindications

Children younger than 12 yr of age ( Oxsoralen lotion); patients exhibiting idiosyncratic reactions to psoralen compounds; patients with a specific history of light-sensitive disease states should not initiate methoxsalen therapy (eg, albinism, erythropoietic protoporphyria, lupus erythematosus, porphyria cutanea tarda, variegate porphyria, xeroderma pigmentosum); patients exhibiting melanoma or possessing a history of melanoma; patients exhibiting invasive squamous cell carcinomas; patients with aphakia, because of increased risk of retinal damage caused by absence of lenses.

Dosage and Administration

Vitiligo
Adults 8-MOP

PO Take 20 mg daily in 1 dose with milk or food 2 to 4 h prior to UV exposure. Take on alternate days and never on 2 consecutive days. Sun exposure is based on basic skin color. Initial sun exposure should be 15 min for light skin, 20 min for medium-colored skin, and 25 min for dark skin. The second, third, and fourth exposures may be increased by 5 min/each exposure (if basic skin color is light, the second exposure can be increased to 20 min, the third exposure to 25 min, and the fourth exposure to 30 min). Subsequent exposures may gradually be increased based on erythema and tenderness of amelanotic skin (max, 0.6 mg/kg).

Adults and Children 12 yr of age and older Oxsoralen lotion

Apply lotion to a small, well-defined, vitiliginous lesion, then expose this area to UVA light. Initial exposure time must not exceed one-half the minimal erythema dose. Regulate treatment intervals by erythema response (once weekly or less, depending on the results). Pigmentation may begin after a few weeks; significant repigmentation may take up to 6 to 9 mo. Periodic treatment may be needed to retain the new pigmentation.

Psoriasis
Adults Oxsoralen-Ultra

PO Take with food or milk 1.5 to 2 h prior to UVA exposure.

8-MOP

PO Take with food or milk 2 h prior to UVA exposure. Take according to the following recommendations: Generally, elderly patients should be started at the low end of the dose recommended according to body weight and closely monitored during ultraviolet A photochemotherapy (PUVA) therapy. No treatments should be given more often than once every other day because the full extent of phototoxic reactions may not be evident until 48 h after each exposure. Dosage may be increased by 10 mg after the fifteenth treatment. Patients weighing:

  • less than 30 kg, give 10 mg
  • 30 to 50 kg, give 20 mg
  • 51 to 65 kg, give 30 mg
  • 66 to 80 kg, give 40 mg
  • 81 to 90 kg, give 50 mg
  • 91 to 115 kg, give 60 mg
  • more than 115 kg, give 70 mg.
Cutaneous T-Cell Lymphoma
Adults Uvadex

Extracorporeal with the UVAR photopheresis system only. (Not for parenteral administration.)

Normal treatment schedule

Treatment is given on 2 consecutive days every 4 wk for a minimum of 7 treatment cycles (6 mo).

Accelerated treatment schedule

If assessment of the patient during the fourth treatment cycle (approximately 3 mo) reveals an increased skin score from the baseline score, the frequency of treatment may be increased to 2 consecutive treatments every 2 wk. If a 25% improvement in the skin score is attained after 4 consecutive wk, the regular treatment schedule may be resumed (max, 20 cycles). Consult UVAR Photopheresis System Operator's Manual before using this product. Treatment involves collection of leukocytes, photoactivation, and reinfusion of photoactivated cells. During each photopheresis treatment, Uvadex 200 mcg (10 mL) is injected directly into photoactivation bag during the first buffy coat collection cycle. At the end of 6 cycles, a total of 740 mL (240 mL of buffy coat, 300 mL of plasma, and 200 mL of normal saline priming fluid) is collected and mixed with the Uvadex 200 mcg present in the photoactivation bag. After photoactivation, the cells are reinfused.

General Advice

  • 8-MOP capsules, Oxsoralen-Ultra capsules: Consult the manufacturer's information for specific UVA radiation source specifications and information, as well as the PUVA treatment protocol.

Storage/Stability

Store at controlled room temperature (59° to 86°F).

Drug Interactions

Known photosensitizers (eg, anthralin, coal tar, coal tar derivatives, fluoroquinolone antibiotics, griseofulvin, halogenated salicylanilides, nalidixic acid, organic staining dyes [eg, methylene blue, methyl orange, rose bengal, toluidine blue], phenothiazines, sulfonamides, tetracyclines, thiazide diuretics)

Exercise care when using these agents and methoxsalen concurrently.

Laboratory Test Interactions

None well documented.

Adverse Reactions

Cardiovascular

8-MOP , Oxsoralen-Ultra

Hypotension.

Uvadex

Hypotension (secondary to extracorporeal volume [more than 1%]).

CNS

8-MOP , Oxsoralen-Ultra

Depression, dizziness, headache, insomnia, malaise, nervousness.

Dermatologic

8-MOP , Oxsoralen-Ultra

Pruritus (10%); cutaneous tenderness, erythema, extension of psoriasis, folliculitis, hypopigmentation, nonspecific rash, urticaria, vesiculation and bullae formations.

Oxsoralen lotion

Severe burns from overexposure to UVA.

GI

8-MOP , Oxsoralen-Ultra

Nausea (10%); GI disturbances.

Miscellaneous

8-MOP , Oxsoralen-Ultra

Edema, herpes simplex, leg cramps, miliaria.

Uvadex

Infection.

Precautions

Warnings

Methoxsalen should only be used by health care providers who have special competence in the diagnosis and treatment of psoriasis and vitiligo ( 8-MOP , Oxsoralen-Ultra ) or cutaneous T-cell lymphoma ( Uvadex ) and who have special training and experience in photochemotherapy. For treatment of patients with psoriasis, restrict photochemotherapy to patients with severe, recalcitrant, disabling psoriasis that is not adequately responsive to other forms of therapy, and only when the diagnosis is certain. 8-MOP may not be interchanged with Oxsoralen-Ultra capsules without retitration of the patient. Oxsoralen-Ultra has greater bioavailability and earlier photosensitization onset time than previous forms. Fully inform patient of the possibilities of ocular damage, aging of the skin, and skin cancer.


Monitor

8-MOP , Oxsoralen-Ultra : Patients should have an ophthalmologic examination prior to the start of therapy and then yearly. Prior to starting therapy and 6 to 12 mo subsequently, patients should have the following tests: CBC, antinuclear antibodies, LFTs, and renal function tests.


Pregnancy

Category C ( 8-MOP , Oxsoralen lotion, Oxsoralen-Ultra ); Category D ( Uvadex ).

Lactation

Undetermined.

Children

Safety and efficacy not established.

Oxsoralen lotion

Safety and efficacy not established in children younger than 12 yr of age.

Elderly

Use with caution, usually starting at the low end of the dosage range, because of the greater frequency of decreased hepatic, renal, or cardiac function, and concomitant diseases or other drug therapy. Use with particular caution in patients with preexisting history of cataract, CV conditions, kidney and/or liver dysfunction, or skin cancer.

Hepatic Function

Because hepatic biotransformation is necessary for drug urinary excretion, use with caution.

Carcinogenesis

Risk of squamous cell carcinoma among PUVA-treated patients is increased (especially in patients who are fair-skinned or have had pre-PUVA exposure to prolonged tar and UVB treatment) ionizing radiation, or arsenic. Risk of basal cell carcinoma may also be increased.

Special Risk Patients

Diligently observe and treat patients with basal cell carcinoma or a history of basal cell carcinoma; diligently observe patients with a history of previous x-ray therapy, grenz ray therapy, or arsenic therapy for signs of carcinoma; patients with cardiac disease or others who may be unable to tolerate prolonged standing or exposure to heat stress should not be treated in a vertical UVA chamber.

Actinic degeneration

Exposure to sunlight and/or UV radiation may result in premature aging of the skin.

Cataract

Because the concentration of methoxsalen in the lens is proportional to the serum level, if the lens is exposed to UVA while methoxsalen is present, photochemical action may lead to irreversible binding of the methoxsalen to proteins and DNA components of the lens.

Skin burning

Serious burns from either UVA or sunlight, even through window glass, can result if recommended dosage and/or exposure schedules are not maintained.

Sunbathing

The presence of sunburn may prevent the accurate evaluation of the patient's response to photochemotherapy.

Total dosage

Total cumulative dose of UVA that can be given safely over long periods of time has not been established.

Overdosage

Symptoms

Severe burns from overexposure to UVA.

Patient Information

  • Advise patient that response to therapy is not rapid and that it may take weeks to months to achieve max benefit.
  • Advise patient that ingesting limes, figs, parsley, parsnips, mustard, carrots, or celery might cause an exaggerated response to the UVA treatments or the sun and to ingest carefully until tolerance is determined.
  • Capsules
  • Advise patient to read the Patient Package Insert before starting therapy and with each refill.
  • Advise patient that nausea is a common side effect and to take each dose with food or milk to minimize this problem. If nausea still occurs, advise patient to divide the dose into 2 portions taken approximately 30 min apart with food or milk.
  • Caution patient to take the dose exactly as prescribed and to carefully follow the timing recommendations between taking the dose and starting the UVA treatment. Advise patient that serious burns can result if drug dosing schedules and/or UVA exposure schedules are not followed.
  • Instruct patient to wear UVA-absorbing, wraparound sunglasses for the 24-h period following ingestion of methoxsalen, whether exposed to direct or indirect sunlight outside or through a glass window.
  • Caution patient not to sunbathe during the 24 h prior to and 48 h after taking methoxsalen and UVA treatment.
  • Caution patient to avoid exposure to sunlamps and the sun, even through windows or cloud cover, for at least 8 h after taking methoxsalen. If sun exposure cannot be avoided, instruct patient to wear protective devices (eg, hat, gloves), and/or apply sunscreen that filters out UVA radiation (“UVA protection”) with a sun protection factor (SPF) of 15 or more. Instruct patient to apply sunscreen to all areas that might be exposed to the sun, including lips, but not to apply until after the UVA treatment.
  • Advise patient that if itching occurs in UVA-treated areas, to frequently apply a bland emollient. If itching persists or worsens, advise patient to notify health care provider.
  • Advise patient to frequently examine skin for small growths or sores that do not heal. Instruct patient to inform health care provider immediately if noted.
  • Caution patients that during PUVA therapy, total UVA-absorbing/blocking goggles mechanically designed to give max ocular protection must be worn. Failure to do so may increase the risk of cataract formation. Abdominal skin, breasts, genitalia, and other sensitive areas should be protected for approximately 33% of the initial exposure time until tanning occurs. Unless affected by disease, male genitalia should be shielded.
  • Caution patients that after combined methoxsalen/UVA therapy, UVA-absorbing wraparound sunglasses should be worn during the daylight for 24 h after combined methoxsalen/UVA therapy.
  • Advise patient to notify health care provider if nausea, itching, redness, tenderness, or blistering of skin occurs and lasts more than 24 to 48 h.
  • Lotion
  • Advise patient that lotion will be applied by a health care provider in a health care setting before undergoing UVA treatment.
  • Instruct patient to keep the treated areas protected from sunlight by wearing protective clothing or applying a sunscreen with UVA protection and an SPF of 15 or more. Advise patient that the area of application may be highly sensitive to sunlight or sunlamps for several days after application.
  • Solution
  • Advise patient that blood will be drawn and sent to the lab where this medication will be used to treat the patient's white blood cells. Once the treatment has been completed, the treated white blood cells will be returned to their body.
  • Instruct patient to wear UVA-absorbing, wraparound sunglasses and to cover exposed skin or use a sunblock with UVA protection and an SPF of 15 or more for the 24-h period following treatment.

Copyright © 2009 Wolters Kluwer Health.

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