Drug Interaction Between Methotrexate and Febuxostat
Febuxostat significantly increases the risk of methotrexate toxicity, particularly hepatotoxicity and hematologic events, and should be avoided or used with extreme caution when patients are receiving methotrexate therapy.
Mechanism of Interaction
Febuxostat inhibits breast cancer resistance protein (BCRP), a critical drug transporter responsible for methotrexate elimination from the liver, kidney, and gastrointestinal tract 1. This inhibition leads to:
- Elevated and prolonged serum methotrexate levels
- Accumulation of methotrexate's toxic metabolite (hydroxymethotrexate)
- Reduced hepatic clearance of methotrexate
Clinical Evidence of Toxicity
Hepatotoxicity (Most Significant Risk)
Concomitant febuxostat substantially increases methotrexate-induced liver damage 1. The FDA Adverse Event Reporting System revealed a reporting odds ratio of 4.16 (95% CI: 2.89-5.98) for hepatotoxicity when febuxostat is combined with methotrexate 1. Laboratory studies confirmed that febuxostat co-administration significantly decreased cell viability and increased cytotoxicity in liver cells exposed to methotrexate 1.
Hematologic Toxicity
Analysis of 810 intravenous methotrexate users showed a disproportionate number of hematologic events (pancytopenia and neutropenia) in patients concomitantly using febuxostat (P < 0.01) 2. This risk is particularly elevated in patients ≥60 years old receiving intravenous methotrexate 2.
The interaction appears more pronounced with intravenous methotrexate compared to oral administration, likely due to BCRP's role in hepatic elimination 2.
Clinical Recommendations
Absolute Precautions
- Avoid febuxostat in patients receiving high-dose methotrexate (such as for osteosarcoma or lymphoma)
- Avoid febuxostat in patients receiving intravenous methotrexate at any dose
- Exercise extreme caution in patients ≥60 years old if combination cannot be avoided
If Combination is Unavoidable (Low-Dose Oral Methotrexate Only)
Monitor the following parameters weekly for the first month, then every 1-2 weeks:
- Complete blood count with differential and platelets (watch for pancytopenia, neutropenia)
- Liver function tests (AST, ALT, bilirubin, albumin)
- Renal function (creatinine, BUN)
- Clinical signs: fever, mouth ulcers, unexplained bruising/bleeding, nausea, abdominal pain, dark urine
Safer Alternative
Allopurinol is the preferred urate-lowering agent in patients requiring methotrexate therapy 2. The Japanese Adverse Drug Event Report database showed no similar disproportionate hematologic events with allopurinol compared to febuxostat 2.
Important Caveats
While one animal study suggested febuxostat might ameliorate methotrexate-induced lung damage through anti-inflammatory effects 3, this contradicts the robust human clinical evidence demonstrating increased toxicity. Do not rely on potential protective effects—the human data clearly shows net harm 2, 1.
The FDA drug label for methotrexate warns about drugs that interfere with renal secretion and mentions NSAIDs specifically 4, but does not yet include febuxostat. However, the BCRP-mediated interaction is mechanistically distinct and clinically significant based on recent evidence.
Bottom Line Algorithm
Patient on methotrexate needs urate-lowering therapy → Choose allopurinol (adjust for renal function per local guidelines 5)
Patient on febuxostat needs methotrexate → Switch febuxostat to allopurinol before initiating methotrexate
Patient already on both drugs → Discontinue febuxostat, switch to allopurinol, and increase monitoring frequency for 4-6 weeks
High-dose or IV methotrexate planned → Febuxostat is contraindicated; ensure allopurinol or alternative urate management