Drug General Information (ID: DDIYZTPINQ)
Drug Name			Trimethoprim		Drug Info		Mercaptopurine		Drug Info
Drug Type		Small molecule				Small molecule
Therapeutic Class		Antiinfective Agents				Antineoplastics
Structure

Mechanism of Trimethoprim-Mercaptopurine Interaction (Severity Level: Moderate)
Additive myelosuppressive effects Click to Show/Hide Mechanism Graph
Drug Name		Trimethoprim				Mercaptopurine
Mechanism		Myelosuppressive effects				Myelosuppressive effects
Key Mechanism Factor 1
		Factor Name		Myelosuppressive effects
		Factor Description		Myelosuppression, also known as bone marrow suppression, is a decrease in bone marrow activity that leads to a decrease in the production of blood cells. Some blood cell disorders include: erythrocytopenia (anemia), leukopenia (neutropenia), and thrombocytopenia (thrombocytopenia).
Mechanism Description		Additive myelosuppressive effects by the combination of Trimethoprim and Mercaptopurine

Recommended Action
Management		Close clinical and laboratory monitoring for the development of hematologic adverse effects is recommended both during and after discontinuation of therapy. Dosage adjustment of azathioprine or mercaptopurine may be considered if an interaction is suspected. Patients should be advised to promptly report symptoms such as chills, fever, malaise, sore throat, mouth sores, unusual fatigue, bruising, or bleeding.

References
1	Bailey RR "Leukopenia due to a trimethoprim-azathioprine interaction." N Z Med J 97 (1984): 739. [PMID: 6595562]
2	Berg KJ, Gjellestad A, Nordby G, et al "Renal effects of trimethoprim in ciclosporin- and azathioprine-treated kidney-allografted patients." Nephron 53 (1989): 218-22. [PMID: 2677807]
3	Canadian Pharmacists Association.
4	Cerner Multum, Inc. "Australian Product Information.".
5	Cerner Multum, Inc. "UK Summary of Product Characteristics.".
6	Product Information. Imuran (azathioprine). Glaxo Wellcome, Research Triangle Park, NC.