Drug Interaction Report

MONITOR: Coadministration with celecoxib may increase the plasma concentrations of drugs that are substrates of the CYP450 2D6 isoenzyme. The mechanism is decreased clearance due to inhibition of CYP450 2D6 activity by celecoxib.

MANAGEMENT: Caution is advised if celecoxib must be used concurrently with medications that undergo metabolism by CYP450 2D6, particularly those with a narrow therapeutic range. Dosage adjustments as well as clinical and laboratory monitoring may be appropriate for some drugs whenever celecoxib is added to or withdrawn from therapy.

GENERALLY AVOID: Patients exposed to photosensitizing agents at the same time as or in the 30 to 90 days following treatment with porfimer may be at an increased risk of a photosensitivity reaction (e.g., erythema, swelling, pruritus, burning sensations, feeling hot, and/or blisters). These agents have each been individually associated with photosensitivity reactions and may have additive effects if used together. Medicinal products with known phototoxic or photoallergic potential include, but are not limited to, hypericin-containing products (e.g., St. John's Wort), griseofulvin, thiazide diuretics, sulfonylureas, phenothiazines, sulfonamides, quinolones, and tetracyclines. Photosensitivity with porfimer is due to residual drug being present in the skin. Porfimer is cleared from a variety of tissues over 40 to 72 hours after treatment, but organs of the reticuloendothelial system (e.g., liver, spleen), skin and the tumor itself retain the drug for a longer period. Patients treated with porfimer will be photosensitive for at least 30 days and possibly up to 90 days or more for patients with hepatic or severe renal dysfunction. In clinical studies of porfimer, photosensitivity reactions occurred in approximately 20% of cancer patients and 69% of high-grade dysplasia in Barrett's esophagus patients.

MANAGEMENT: Use of photosensitizing agents should be avoided for at least 30 days and maybe up to 90 days or longer after porfimer treatment depending on the patient's hepatic function, renal function, and/or ability to tolerate exposure to sunlight. Following treatment with porfimer, patients should follow measures outlined in the product labeling for light and sun exposure. It is important to counsel patients to expose their skin to ambient indoor light as it is not only safe but will help eliminate porfimer through the skin by a process called "photobleaching." Before exposing skin or eyes to direct sunlight or bright indoor light (e.g., examination lamps, dental lamps, operating room lamps, floodlights, halogen lamps, unshaded light bulbs at close proximity, etc.), patients should test for residual photosensitivity as described in porfimer's product labeling.

GENERALLY AVOID: Alcohol may potentiate some of the pharmacologic effects of CNS-active agents. Use in combination may result in additive central nervous system depression and/or impairment of judgment, thinking, and psychomotor skills.

MANAGEMENT: Patients receiving CNS-active agents should be warned of this interaction and advised to avoid or limit consumption of alcohol. Ambulatory patients should be counseled to avoid hazardous activities requiring complete mental alertness and motor coordination until they know how these agents affect them, and to notify their physician if they experience excessive or prolonged CNS effects that interfere with their normal activities.