Methoxsalen Dosage

Medically reviewed by Drugs.com. Last updated on Aug 7, 2023.

Applies to the following strengths: 10 mg; 20 mcg/mL

Usual Adult Dose for:

Psoriasis
Cutaneous T-cell Lymphoma

Additional dosage information:

Renal Dose Adjustments
Liver Dose Adjustments
Dose Adjustments
Precautions
Dialysis

Usual Adult Dose for Psoriasis

**Soft Gelatin Capsules are NOT interchangeable with other dosage forms. The manufacturer product information should be consulted.**

Soft gelatin capsules:

Initial dose: Take capsules orally 1.5 to 2 hours before UVA exposure with some low fat food or milk according to patient weight:
Weight : soft gelatin capsule dose
Under 30 kg: 10 mg
30 to 50 kg: 20 mg
51 to 65 kg: 30 mg
66 to 80 kg: 40 mg
81 to 90 kg: 50 mg
91 to 115 kg: 60 kg
Over 115 kg: 70 mg

The initial UVA exposures are based on the patient's skin type and should be conducted according to the guidelines in professional literature. The manufacturer product information should be consulted.

Maintenance dose: Dose, schedule, and UVA exposure are based on the patients skin type, grades of erythema, and response to therapy per guidelines in professional literature.

Comments:

Administer only in conjunction with a schedule of controlled doses of long wave ultraviolet radiation.
Patients must not sunbathe during the 24 hours prior to taking this drug and UV exposure; presence of a sunburn may prevent accurate evaluation of the patient's response to therapy.
Tell patients emphatically to wear UVA absorbing, wrap-around sunglasses for the 24 hour period following ingestion of this drug whether exposed to direct or indirect sunlight in the open or through a window; the eyewear must be designed to prevent entry of stray radiation to the eyes, including that which may enter from the sides of the eyewear.
Patients must avoid sun exposure, even through window glass or cloud cover, for at least 8 hours after drug ingestion.
If sun exposure cannot be avoided, the patient should wear protective devices such as hats and gloves and/or apply sunscreen that filters out UVA radiation (e.g. sunscreens with benzophenone and/or PABA esters and a sun protective factor of 15 or greater).
Sunscreens should not be applied to psoriasis areas until after UVA treatment.
Total UVA absorbing/blocking goggles mechanically designed to give maximal ocular protection must be worn during PUVA therapy; failure to do so increases the risk of cataract formation. A reliable radiometer can verify elimination of UVA through the goggles.
During PUVA therapy, abdominal skin, breasts, genitalia, and other sensitive areas should be protected for approximately 1/3 of the initial exposure time until tanning occurs; unless affected by psoriasis, male genitalia should be shielded.
Tell patients emphatically to wear UVA absorbing, wrap-around sunglasses for the 24 hour period following ingestion of this drug whether exposed to direct or indirect sunlight in the open or through a window; the eyewear must be designed to prevent entry of stray radiation to the eyes, including that which may enter from the sides of the eyewear.
Patients should not sunbathe for 48 hours after therapy; erythema and/or burning due to photochemotherapy and sunburn from sun exposure are additive.

Use(s): Symptomatic control of severe, recalcitrant, disabling psoriasis not adequately responsive to other forms of therapy and when the diagnosis has been supported by biopsy.

Usual Adult Dose for Cutaneous T-cell Lymphoma

Extracorporeal administration:

Treatment involves collection of leukocytes, photoactivation, and reinfusion of photoactivated cells.
Medication should be injected into the photopheresis system, not directly into patients.
Dosage is calculated for each treatment according to treatment volume.

Treatment volume x 0.017 = mL of Uvadex(R) for each treatment

Normal treatment schedule: Treatment is given on 2 consecutive days every 4 weeks for a minimum of 7 treatment cycles (6 months)

Accelerated treatment schedule: If patient assessment during the 4th treatment cycle (about 3 months) shows an increased skin score from baseline, treatment frequency may be increased to 2 consecutive treatments every 2 weeks.

If a 25% improvement in skin score is attained after 4 weeks, the normal treatment schedule may be resumed.
Patients maintained on accelerated treatment may receive a maximum of 20 cycles.

Duration of therapy: 6 months

Comments:

For use with photopheresis.
There is no evidence showing treatment beyond 6 months or on a different schedule provides additional benefit.

Use(s): Palliative treatment of skin manifestations of cutaneous T-cell lymphoma that is unresponsive to other forms of treatment.

Renal Dose Adjustments

No adjustment recommended.

Although several renal transplant patients with poor renal function received Uvadex(R), little additional information is available on use in renally impaired patients.
No extra precautions (e.g. dose reduction, increased protection from UV light) were taken in the renal transplant patients receiving Uvadex(R) and the procedures were effective and well tolerated

Liver Dose Adjustments

Use with caution.

Hepatic biotransformation is necessary for urinary excretion of this drug.

Dose Adjustments

In general, dose selection for elderly patients should be cautious, usually starting on the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and concomitant diseases or medications.

Precautions

US BOXED WARNING(S):

This drug should only be used by physicians with special competence in the diagnosis and treatment of cutaneous T-cell lymphoma/psoriasis who have special training and experience in use of photochemotherapy; use of this drug and ultraviolet radiation therapy should be under constant supervision of such a physician.
For treatment of psoriasis, photochemotherapy should be restricted to patients with severe, recalcitrant, disabling psoriasis which is not adequately responsive to other therapies and only when the diagnosis is certain.
Methoxsalen capsules USP 10 mg (soft gelatin capsules) exhibit significantly greater bioavailability and earlier photosensitization onset time than previous dosage forms; treat patients in accordance with the dosimetry specifically recommended for this product; determine the minimum phototoxic dose (MPD) and phototoxic peak time prior to onset of photochemotherapy with this dosage.

Recommendations:

Fully inform patients of the possibilities of ocular damage, aging of the skin, and skin cancer (including melanoma).
Methoxsalen soft gelatin capsules should not be used interchangeably with regular methoxsalen hard gelatin capsules.
The manufacturer product information should be consulted prior to using this product.

Safety and efficacy have not been established in patients younger than 18 years.

Consult WARNINGS section for additional precautions.