Drug Interactions between Mepergan and methoxsalen

ADJUST DOSE: The central nervous system and respiratory depressant effects of meperidine may be potentiated by concomitant use of other agents with CNS depressant effects. An increased risk of serious adverse reactions such as respiratory depression, hypotension, profound sedation, syncope, coma, and even death should be considered, particularly in elderly or debilitated patients.

MANAGEMENT: Caution and dosage adjustments are advisable when meperidine is used in combination with other narcotic analgesics, general anesthetics, phenothiazines, sedative-hypnotics, tranquilizers, tricyclic antidepressants, or other CNS depressants such as alcohol. A lower dosage of meperidine should be considered initially, then titrated carefully according to pain level and clinical response. Meperidine dosage reductions of 25% to 50% have been recommended for patients receiving phenothiazines and other tranquilizers. Patients should be advised to avoid rising abruptly from a sitting or recumbent position, and to notify their physician if they experience dizziness, lightheadedness, orthostasis, syncope, tachycardia, or excessive CNS effects that interfere with their normal activities. Patients should also avoid driving or operating hazardous machinery until they know how these medications affect them.

MONITOR: Concomitant use of methoxsalen with other known photosensitizing agents may increase the risk of photosensitivity reactions. These agents include anthralin, coal tar or coal tar derivatives, griseofulvin, hypericin extracts (e.g., St John's Wort), fluoroquinolones, phenothiazines, retinoids, halogenated salicylanilides (bacteriostatic soaps), sulfonamides, sulfonylureas, tetracyclines, thiazides, and certain organic staining dyes such as methylene blue, toluidine blue, rose bengal, and methyl orange.

MANAGEMENT: Caution is advised and pharmacologic response to methoxsalen therapy should be carefully monitored if concomitant use of other photosensitizing agents cannot be avoided. Patients should be advised to avoid sun exposure, even through window glass or cloud cover, for at least 8 hours after methoxsalen ingestion and during the 24 hours following photochemotherapy or photopheresis treatment. Protective devices should be used if sun exposure cannot be avoided, such as a hat and gloves and/or sunscreens containing ingredients that filter out UVA radiation (e.g., benzophenone and/or PABA esters). Sunscreens must be applied to all areas that might be exposed to the sun, including the lips. For the treatment of psoriasis, sunscreens should not be applied to areas affected by psoriasis until after treatment in the UVA chamber. In addition, UVA-absorbing wrap-around sunglasses should be worn during daylight for 24 hours after methoxsalen ingestion and during the 24 hours following photochemotherapy or photopheresis treatment to prevent the irreversible binding of methoxsalen to proteins and DNA components of the lens, which can lead to formation of cataracts. The glasses should be worn any time patients are exposed to direct or indirect sunlight, whether they are outdoors or exposed through a window. Because erythema and/or burning due to photochemotherapy and sunburn due to sun exposure are additive, patients should not sunbathe for 48 hours after photochemotherapy.