Drug General Information (ID: DDIAF72HPI)
Drug Name			Oseltamivir		Drug Info		Methotrexate		Drug Info
Drug Type		Small molecule				Small molecule
Therapeutic Class		Antiviral Agents				Antimetabolites
Structure

Mechanism of Oseltamivir-Methotrexate Interaction (Severity Level: Moderate)
Competitive inhibition of renal tubular secretion Click to Show/Hide Mechanism Graph
Drug Name		Oseltamivir				Methotrexate
Mechanism		Competitive inhibition of renal tubular secretion of methotrexate				Methotrexate
Key Mechanism Factor 1
		Factor Name		Renal tubular secretion
		Factor Description		Renal tubular secretion allows selective transfer of substances from the blood around the capillaries into the renal tubules via filtrate. Drug excretion may be reduced when two drugs compete for renal tubular secretion.
Mechanism Description		Decreased elimination of Methotrexate caused by Oseltamivir mediated competitive inhibition of renal tubular secretion

Recommended Action
Management		If this combination must be used, European drug product labeling recommends that patients should be monitored for signs and symptoms of methotrexate toxicity e.g., bone marrow suppression, hepatotoxicity, and nephrotoxicity. Patients should be advised to promptly report symptoms including fever, chills, sore throat, bruising, bleeding, stomatitis, malaise, shortness of breath, lower extremity edema, jaundice, or change in stool or urine color to their physician.

References
1	Cerner Multum, Inc. "UK Summary of Product Characteristics.".
2	Nesher G, Mates M, Zevin S "Effect of caffeine consumption on efficacy of methotrexate in rheumatoid arthritis." Arthritis Rheum 48 (2003): 571-572. [PMID: 12571869]