Drug Interactions between famotidine / ibuprofen and methyl aminolevulinate topical

MONITOR: Concomitant use of aminolevulinate topical preparations with other known photosensitizing agents may enhance the phototoxic reaction to photodynamic therapy. These agents have each been individually associated with photosensitivity reactions and may have additive effects if administered concurrently. Medicinal products with known phototoxic or photoallergic potential include fluoroquinolones, phenothiazines, retinoids, sulfonamides, sulfonylureas, tetracyclines, thiazide diuretics, griseofulvin, and hypericin extracts (e.g., St John's Wort).

MANAGEMENT: Caution is advised and pharmacologic response to photodynamic therapy should be carefully monitored if concomitant use of other photosensitizing agents cannot be avoided. Patients should be advised to avoid exposure of treated areas to sunlight or bright indoor lights (e.g., examination lamps, operating room lamps, tanning beds, lights at close proximity) during the period between application of aminolevulinic acid or methyl aminolevulinate and photoactivation, and for 48 hours post-illumination. As sunscreen is not effective in protecting treated areas of skin, patients should be counseled to wear protective apparel, such as a wide-brimmed hat, long sleeve shirt, and gloves to protect themselves. Concomitant use with other topical medicinal products should be avoided. Some authorities recommend avoiding use of hypericin-containing products for 2 weeks prior to treatment with topical aminolevulinic acid.

H2 antagonists may alter the pharmacokinetic disposition of some nonsteroidal anti-inflammatory drugs (NSAIDs), resulting in increased or decreased plasma concentrations. Data have been varied, even for the same NSAID. The mechanism may involve inhibition of metabolism, changes in gastric pH resulting in altered absorption, and/or reduced urinary elimination of the affected NSAIDs. Statistically significant changes have been small and of limited clinical significance when interactions have been observed.