TMP-SMX + methotrexate — marrow suppression
- Both can suppress marrow
- TMP-SMX also impairs folate pathways
- Renal methotrexate clearance may fall
- Severe pancytopenia/mucositis can occur
- Avoid combination when possible
- If unavoidable: CBC/Cr + close monitoring
Interaction at a glance
- Avoid combination when possible
- If unavoidable: CBC/Cr + close monitoring
Mechanism
- Both can suppress marrow
- TMP-SMX also impairs folate pathways
Magnitude / time course
- Renal methotrexate clearance may fall
- Severe pancytopenia/mucositis can occur
Monitoring
- Avoid combination when possible
- If unavoidable: CBC/Cr + close monitoring
Self-check
- What is the preferred management of TMP-SMX + methotrexate?
Avoid combination when possible.
- Should TMP-SMX + methotrexate generally be combined?
No—avoid the combination when feasible.
Drugs in this interaction (3)
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