Methoxsalen

METHOXSALEN- methoxsalen capsule, liquid filled
Actavis Pharma, Inc.

(Soft Gelatin Capsules)

Rx Only

CAUTION: METHOXSALEN IS A POTENT DRUG. READ ENTIRE BROCHURE PRIOR TO PRESCRIBING OR DISPENSING THIS MEDICATION.

Methoxsalen with UV radiation should be used only by physicians who have special competence in the diagnosis and treatment of psoriasis and who have special training and experience in photochemotherapy. The use of Psoralen and ultraviolent radiation therapy should be under constant supervision of such a physician. For the treatment of patients with psoriasis, photochemotherapy should be restricted to patients with severe, recalcitrant, disabling psoriasis which is not adequately responsive to other forms of therapy, and only when the diagnosis is certain. Because of the possibilities of ocular damage, aging of the skin, and skin cancer (including melanoma), the patient should be fully informed by the physician of the risks inherent in this therapy.

CAUTION: Methoxsalen Capsules, USP (Soft Gelatin Capsules) should not be used interchangeably with regular methoxsalen capsules or methoxsalen hard gelatin capsules. This new dosage form of methoxsalen exhibits significantly greater bioavailability and earlier photosensitization onset time than previous methoxsalen dosage forms. Patient should be treated in accordance with the dosimetry specifically recommended for this product. The minimum phototoxic dose (MPD) and phototoxic peak time after drug administration prior to onset of photochemotherapy with this dosage form should be determined.

DESCRIPTION

Methoxsalen Capsules, USP (Soft Gelatin Capsules) 10 mg (8-methoxypsoralen). Methoxsalen, USP is a naturally occurring photoactive substance found in the seeds of the Ammi majus (Umbelliferae) plant and in the roots of Heracleum Candicans. It belongs to a group of compounds known as psoralens, or furocoumarins. The chemical name of methoxsalen, USP is 9-methoxy-7H-furo [3,2-g] [1] benzopyran-7-one; it has the following structure:

a8ea5063-figure-01

Each liquid filled soft-gelatin methoxsalen capsule contains 10 mg of Methoxsalen, USP and the following inactive ingredients: D&C yellow #10, FD&C blue #1, FD&C red #40, gelatin, glycerin, methylparaben sodium, polyethylene glycol, propylparaben sodium, purified water, sorbital sorbitan solution and titanium dioxide.

CLINICAL PHARMACOLOGY

The combination treatment regimen of psoralen (P) and ultraviolet radiation of 320 to 400 nm wavelength commonly referred to as UVA is known by the acronym, PUVA. Skin reactivity to UVA (320 to 400 nm) radiation is markedly enhanced by the ingestion of methoxsalen. In a well controlled bioavailability study, Methoxsalen Capsules, USP (Soft Gelatin Capsules) reached peak drug levels in the blood of test subjects between 0.5 and 4 hours (Mean = 1.8 hours) as compared to between 1.5 and 6 hours (Mean = 3.0 hours) for regular methoxsalen when administered with 8 ounces of milk. Peak drug levels were 2 to 3 fold greater when the overall extent of drug absorption was approximately two fold greater for Methoxsalen Capsules, USP (Soft Gelatin Capsules) as compared to regular methoxsalen capsules. Detectable methoxsalen levels were observed up to 12 hours post dose. The drug half-life is approximately 2 hours. Photosensitivity studies demonstrate a shorter time of peak photosensitivity of 1.5 to 2.1 hours vs. 3.9 to 4.25 hours for regular methoxsalen capsules. In addition, the mean minimal erythema dose (MED), J/cm2 , for the Methoxsalen Capsules, USP (Soft Gelatin Capsules) are substantially less than that required for regular methoxsalen capsules (Levins et al., 1984 and private communication1).

Methoxsalen is reversibly bound to serum albumin and is also preferentially taken up by epidermal cells (Artuc et al., 19792). At a dose which is six times larger than that used in humans, it induces mixed function oxidases in the liver of mice (Mandula et al., 19783). In both mice and man, methoxsalen is rapidly metabolized. Approximately 95% of the drug is excreted as a series of metabolites in the urine within 24 hours (Pathak et al., 19774). The exact mechanism of action of methoxsalen with the epidermal melanocytes and keratinocytes is not known. The best known biochemical reaction of methoxsalen is with DNA. Methoxsalen, upon photoactivation, conjugates and forms covalent bonds with DNA which leads to the formation of both monofunctional (addition to a single strand of DNA) and bifunctional (crosslinking of psoralen to both strands of DNA) adducts (Dall’ Acqua et al., 19715 ; Cole, 19706 ; Musajo et al., 19747 ; Dall’ Acqua et al., 19798). Reactions with proteins have also been described (Yoshikawa, et al., 19799).

Methoxsalen acts as a photosensitizer. Administration of the drug and subsequent exposure to UVA can lead to cell injury. Orally administered methoxsalen reaches the skin via the blood and UVA penetrates well into the skin. If sufficient cell injury occurs in the skin, an inflammatory reaction occurs. The most obvious manifestation of this reaction is delayed erythema, which may not begin for several hours and peaks at 48 to 72 hours. The inflammation is followed, over several days to weeks, by repair which is manifested by increased melanization of the epidermis and thickening of the stratum corneum. The mechanisms of therapy are not known. In the treatment of psoriasis, the mechanism is most often assumed to be DNA photo damage and resulting decrease in cell proliferation but other vascular, leukocyte, or cell regulatory mechanisms may also be playing some role. Psoriasis is a hyper-proliferative disorder and other agents known to be therapeutic for psoriasis are known to inhibit DNA synthesis.

INDICATIONS AND USAGE

Photochemotherapy (Methoxsalen with long wave UVA radiation) is indicated for the symptomatic control of severe, recalcitrant, disabling psoriasis not adequately responsive to other forms of therapy and when the diagnosis has been supported by biopsy. Methoxsalen Capsules, USP (Soft Gelatin Capsules) are intended to be administered only in conjunction with a schedule of controlled doses of long wave ultraviolet radiation.

CONTRAINDICATIONS

  1. Patients exhibiting idiosyncratic reactions to psoralen compounds.
  2. Patients possessing a specific history of light sensitive disease states should not initiate methoxsalen therapy except under special circumstances. Diseases associated with photosensitivity include lupus erythematosus, porphyria cutanea tarda, erythropoietic protoporphyria, variegate porphyria, xeroderma pigmentosum, and albinism.
  3. Patients with melanoma or with a history of melanoma.
  4. Patients with invasive squamous cell carcinomas.
  5. Patients with aphakia, because of the significantly increased risk of retinal damage due to the absence of lenses.

WARNINGS-GENERAL

Skin Burning

Serious burns from either UVA or sunlight (even through window glass) can result if the recommended dosage of the drug and/or exposure schedules are exceeded.

Carcinogenicity

Animal studies

Topical or intraperitoneal methoxsalen has been reported to be a potent photocarcinogen in albino mice and hairless mice (Hakim et al., 196010). However, methoxsalen given by the oral route to Swiss albino mice suggests this agent exerts a protective effect against ultraviolet carcinogenesis; mice given 8-methoxypsoralen in their diet showed 38% ear tumors 180 days after the start of ultraviolet therapy compared to 62% for controls (O’Neal et al., 195711).

Human studies

A 5.7 year prospective study of 1380 psoriasis patients treated with oral methoxsalen and ultraviolet A photochemotherapy (PUVA) demonstrated that the risk of cutaneous squamous-cell carcinoma developing at least 22 months following the first PUVA exposure was approximately 12.8 times higher in the high dose patients than in the low dose patients (Stern et al., 197912 , Stern et al., 198013 , and Stern et al., 198414). The substantial dose-dependent increase was observed in patients with neither a prior history of skin cancer nor significant exposure to cutaneous carcinogens. Reduction in PUVA dosage significantly reduces the risk. No substantial dose related increase was noted for basal cell carcinoma according to Stern et al., 198414. Increases appear greatest in patients who have pre-PUVA exposure to 1) prolonged tar and UVB treatment, 2) ionizing radiation, or 3) arsenic.

Roenigk et al., 198015 , studied 690 patients for up to 4 years and found no increase in the risk of non-melanoma skin cancer, although patients in this cohort had significantly less exposure to PUVA than in the Stern et al. study. Recent analysis of new data in the Stern et al cohort (Stern et al., 199716) has shown that these patients have an elevated relative risk of contracting melanoma. The relative risk for melanoma in these patients was 2.3 (95 percent confidence interval 1.1 to 4.1). The risk is particularly higher in those patients who have received more than 250 PUVA treatments and in those whose treatment has spanned greater than 15 years earlier. These observations indicate the need for monitoring of PUVA patients for skin tumors throughout their lives.

In a study in Indian patients treated for 4 years for vitiligo, 12 percent developed keratoses, but not cancer, in the depigmented, vitiliginous areas (Mosher, 198017). Clinically, the keratoses were keratotic papules, actinic keratosis-like macules, nonscaling dome-shaped papules, and lichenoid porokeratotic-like papules.

Cataractogenicity

Animal Studies

Exposure to large doses of UVA causes cataracts in animals, and this effect is enhanced by the administration of methoxsalen (Cloud et al., 196018 ; Cloud et al., 196119 Freeman et al., 196920).

Human Studies

It has been found that the concentration of methoxsalen in the lens is proportional to the serum level. If the lens is exposed to UVA during the time methoxsalen is present in the lens, photochemical action may lead to irreversible binding of methoxsalen to proteins and the DNA components of the lens (Lerman et al., 198021). However, if the lens is shielded from UVA, the methoxsalen will diffuse out of the lens in a 24 hour period (Lerman et al., 198021). Patients should be told emphatically to wear UVA absorbing, wrap-around sunglasses for the twenty-four (24) hour period following ingestion of methoxsalen whether exposed to direct or indirect sunlight in the open or through a window glass.

Among patients using proper eye protection, there is no evidence for a significantly increased risk of cataracts in association with PUVA therapy (Stern et al., 197912). Thirty-five of 1380 patients have developed cataracts in the five years since their first PUVA treatment. This incidence is comparable to that expected in a population of this size and age distribution. No relationship between PUVA dose and cataract risk in this group has been noted.

Actinic Degeneration

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

Basal Cell Carcinomas

Patients exhibiting multiple basal cell carcinomas or having a history of basal cell carcinomas should be diligently observed and treated.

Radiation Therapy

Patients having a history of previous x-ray therapy or grenz ray therapy should be diligently observed for signs of carcinoma.

Arsenic Therapy

Patients having a history of previous arsenic therapy should be diligently observed for signs of carcinoma.

Hepatic Diseases

Patients with hepatic insufficiency should be treated with caution since hepatic biotransformation is necessary for drug urinary excretion.

Cardiac Diseases

Patients with cardiac diseases or others who may be unable to tolerate prolonged standing or exposure to heat stress should not be treated in a vertical UVA chamber.

Elderly Patients

Caution should be used in elderly patients, especially those with a pre-existing history of cataracts, cardiovascular conditions, kidney and/or liver dysfunction, or skin cancer.

Total Dosage

The total cumulative dose of UVA that can be given over long periods of time with safety has not as yet been established.

Concomitant Therapy

Special care should be exercised in treating patients who are receiving concomitant therapy (either topically or systemically) with known photosensitizing agents such as anthralin, coal tar or coal tar derivatives, griseofulvin, phenothiazines, nalidixic acid, fluoroquinolone antibiotics, halogenated salicylanilides (bacteriostatic soaps), sulfonamides, tetracyclines, thiazides and certain organic staining dyes such as methylene blue, toluidine blue, rose bengal, and methyl orange.

All MedLibrary.org resources are included in as near-original form as possible, meaning that the information from the original provider has been rendered here with only typographical or stylistic modifications and not with any substantive alterations of content, meaning or intent.

This site is provided for educational and informational purposes only, in accordance with our Terms of Use, and is not intended as a substitute for the advice of a medical doctor, nurse, nurse practitioner or other qualified health professional.

Privacy Policy | Copyright © 2020. All Rights Reserved.