Drug interactions
Methotrexate + Nafcillin
Severity: Major
Methotrexate and Nafcillin: major interaction.
Last updated Sources: US FDA label
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Penicillins can raise methotrexate serum concentrations, leading to myelosuppression, mucositis and gastrointestinal toxicity. The effect has been described at both low and high methotrexate doses.
What this interaction means in plain words
Methotrexate and Nafcillin can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Why it happens
Competition for renal tubular secretion reduces methotrexate renal clearance.
What to do
Monitor methotrexate levels where feasible, and check blood counts and renal function. Consider an alternative antibiotic, especially with high-dose methotrexate.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
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References
Other interactions of Methotrexate
- Acitretin + Methotrexate Contraindicated
- Adenovirus types 4 and 7 live + Methotrexate Contraindicated
- Influenza virus vaccine quadrivalent intranasal + Methotrexate Contraindicated
- Ketorolac + Methotrexate Contraindicated
- Measles mumps and rubella vaccine live + Methotrexate Contraindicated
- Measles mumps and rubella vaccine + Methotrexate Contraindicated
Frequently asked questions
Can I take Methotrexate with Nafcillin?
MediHelp rates the interaction as major. Methotrexate and Nafcillin can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Penicillins can raise methotrexate serum concentrations, leading to myelosuppression, mucositis and gastrointestinal toxicity. The effect has been described at both low and high methotrexate doses.
How serious is the interaction between Methotrexate and Nafcillin?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor methotrexate levels where feasible, and check blood counts and renal function. Consider an alternative antibiotic, especially with high-dose methotrexate.
What other medicines interact with Methotrexate?
MediHelp also lists interactions of Methotrexate with, for example, Acitretin, Adenovirus types 4 and 7 live, Influenza virus vaccine quadrivalent intranasal. The full list is on the Methotrexate page.
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