Methotrexateinteractions

Oral Antibiotics: May increase hematologic and gastrointestinal toxicity. Monitor patients accordingly.

Nitrous Oxide: May increase the risk of toxicity. NSAIDs, Aspirin, and Steroids: May elevate and prolong serum methotrexate levels and increase gastrointestinal toxicity. Monitor patients accordingly.

7.1 Effect of

Other Drugs on XATMEP Oral Antibiotics Penicillins may reduce the renal clearance of methotrexate; increased serum concentrations of methotrexate with concomitant hematologic and gastrointestinal toxicity have been observed with methotrexate. Monitor patients accordingly. Trimethoprim/sulfamethoxazole has been reported to increase bone marrow suppression in patients receiving methotrexate. Monitor patients accordingly. Hepatotoxins The potential for increased hepatotoxicity when methotrexate is administered with other hepatotoxic agents has not been evaluated; however, hepatotoxicity has been reported in such cases. Monitor patients receiving XATMEP with other potential hepatotoxins (e.g., azathioprine, retinoids, and sulfasalazine) for possible signs of hepatotoxicity. Probenecid Probenecid may reduce renal elimination of methotrexate. Consider alternative drugs. Nitrous Oxide The use of nitrous oxide anesthesia potentiates the effect of methotrexate on folate-dependent metabolic pathways, resulting in the potential for increase toxicity. Avoid the simultaneous use of nitrous oxide and methotrexate. Nonsteroidal Anti-Inflammatory Drugs (NSAIDs), Aspirin, and Steroids Concomitant administration of some NSAIDs with high dose methotrexate therapy has been reported to elevate and prolong serum methotrexate levels, resulting in deaths from severe hematologic and gastrointestinal toxicity. Caution should be used when NSAIDs and salicylates are administered concomitantly with lower doses of methotrexate, including XATMEP. These drugs have been reported to reduce the tubular secretion of methotrexate in an animal model and may enhance its toxicity. Despite the potential interactions, studies of methotrexate in patients with rheumatoid arthritis, including patients with polyarticular juvenile idiopathic arthritis (pJIA), have usually included concurrent use of constant dosage regimens of NSAIDs, without apparent problems. It should be appreciated, however, that the doses used in pJIA (10 mg/m 2 /week as starting dose) are somewhat lower than those used in acute lymphoblastic leukemia and that larger doses could lead to unexpected toxicity. Aspirin, NSAIDs, and/or low dose steroids may be continued, although the possibility of increased toxicity with concomitant use of NSAIDs including salicylates has not been fully explored. Steroids may be reduced gradually in patients who respond to methotrexate.

7.2 Effect of XATMEP on

Other Drugs Theophylline Methotrexate may decrease the clearance of theophylline. Monitor theophylline levels when coadministered with XATMEP.