Drug General Information (ID: DDIKRHCOF3)
Drug Name			Methotrexate		Drug Info		Sulfamethizole		Drug Info
Drug Type		Small molecule				Small molecule
Therapeutic Class		Antimetabolites				Antiinfective Agents
Structure

Mechanism of Methotrexate-Sulfamethizole Interaction (Severity Level: Moderate)
Competitive binding of plasma proteins Click to Show/Hide Mechanism Graph
Drug Name		Methotrexate				Sulfamethizole
Mechanism		Competition for plasma protein binding sites				Competition for plasma protein binding sites
Key Mechanism Factor 1
		Factor Name		Plasma protein binding
		Factor Description		Plasma protein binding refers to the degree of binding of a drug to proteins in the blood, and the lower the degree of binding, the more efficiently the drug can cross cell membranes or diffuse. Plasma protein binding alters the distribution and therapeutic characteristics of the drugs.
Mechanism Description		Increased plasma concentration of Sulfamethizole and Methotrexate due to competitive binding of plasma proteins

Recommended Action
Management		Caution is advised when methotrexate is used with sulfonamides. Complete blood counts, liver enzymes, and serum creatinine levels should be performed at baseline and periodically during treatment. Patients should be closely monitored for increased methotrexate adverse effects including nausea, vomiting, diarrhea, stomatitis, alopecia, anemia, bone marrow suppression (e.g., aplastic anemia, leukopenia, neutropenia, thrombocytopenia., pancytopenia), hepatotoxicity, and nephrotoxicity.

References
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10	Product Information. Bactrim (trimethoprim-sulfamethoxazole). Roche Laboratories, Nutley, NJ.
11	Product Information. Rheumatrex (methotrexate). Lederle Laboratories, Wayne, NJ.
12	Product Information. Sulfadiazine (sulfadiazine). Eon Labs Manufacturing Inc, Laurelton, NY.
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