METHOXSALEN Drug Interactions: What You Need to Know

D. DRUG INTERACTIONS: See WARNINGS – GENERAL.

CONTRAINDICATIONS UVADEX ® (methoxsalen)

Sterile

Solution is contraindicated in patients exhibiting idiosyncratic or hypersensitivity reactions to methoxsalen, other psoralen compounds or any of the excipients. Patients possessing a specific history of a light sensitive disease state should not initiate methoxsalen therapy. Diseases associated with photosensitivity include lupus erythematosus, porphyria cutanea tarda, erythropoietic protoporphyria, variegate porphyria, xeroderma pigmentosum and albinism. UVADEX ® Sterile Solution is contraindicated in patients with aphakia, because of the significantly increased risk of retinal damage due to the absence of lenses. Patients should not receive UVADEX ® if they have any contraindications to the photopheresis procedure.

V. WARNINGS - GENERAL A. 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. B. CARCINOGENICITY: ANIMAL STUDIES: Topical or intraperitoneal methoxsalen has been reported to be a potent photocarcinogen in albino mice and hairless mice (Hakim et al., 1960 10 ). 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., 1957 11 ). 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., 1979 12 , Stern et al., 1980 13 , and Stern et al., 1984 14 ). 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., 1984 14 . 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., 1980 15 , 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., 1997 16 ) 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% 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. Some patients developing melanoma did so even after having ceased PUVA therapy over 5 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% developed keratoses, but not cancer, in the depigmented, vitiliginous areas (Mosher, 1980 17 ). Clinically, the keratoses were keratotic papules, actinic keratosis-like macules, nonscaling dome-shaped papules, and lichenoid porokeratotic-like papules. C. 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., 1960 18 ; Cloud et al., 1961 19 Freeman et al., 1969 20 ). 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., 1980 21 ). However, if the lens is shielded from UVA, the methoxsalen will diffuse out of the lens in a 24-hour period (Lerman et al., 1980 21 ). Patients should be told emphatically to wear UVA absorbing, wrap-around sunglasses for the 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., 1979 12 ). Thirty-five of 1380 patients have developed cataracts in the 5 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. D. ACTINIC DEGENERATION: Exposure to sunlight and/or ultraviolet radiation may result in "premature aging" of the skin. E. BASAL CELL CARCINOMAS: Patients exhibiting multiple basal cell carcinomas or having a history of basal cell carcinomas should be diligently observed and treated. F. RADIATION THERAPY: Patients having a history of previous x-ray therapy or grenz ray therapy should be diligently observed for signs of carcinoma. G. ARSENIC THERAPY: Patients having a history of previous arsenic therapy should be diligently observed for signs of carcinoma. H. HEPATIC DISEASES: Patients with hepatic insufficiency should be treated with caution since hepatic biotransformation is necessary for drug urinary excretion. I. 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. J. GERIATRIC 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. K. 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. L. 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.