Common Drug Interactions with Methotrexate
Methotrexate, used for rheumatoid arthritis, psoriasis, and cancer, interacts with many drugs by competing for renal excretion, inhibiting protein binding, or boosting toxicity via shared pathways like folate antagonism.[1] Key interactions raise risks of bone marrow suppression, kidney damage, gastrointestinal bleeding, or hepatotoxicity.
Drugs That Increase Methotrexate Toxicity
Nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen, naproxen, and aspirin reduce methotrexate clearance, leading to elevated blood levels and severe side effects such as myelosuppression or acute renal failure.[1][2]
Proton pump inhibitors (PPIs) including omeprazole and pantoprazole inhibit methotrexate's renal secretion via organic anion transporters, prolonging exposure—hospitalizations have increased with high-dose PPI use.[1][3]
Penicillins (e.g., amoxicillin) and probenecid displace methotrexate from proteins and block tubular secretion, causing prolonged toxicity.[1]
Trimethoprim-sulfamethoxazole (Bactrim) competes for folate metabolism, amplifying bone marrow suppression.[2]
Interactions with Alcohol and Hepatotoxic Agents
Alcohol consumption, even moderate, heightens hepatotoxicity risk when combined with methotrexate, due to additive liver stress—weekly limits are advised, but abstinence is often recommended.[1][2]
Other hepatotoxins like retinoids (e.g., isotretinoin) or leflunomide worsen liver enzyme elevations.[1]
Disease-Modifying Antirheumatic Drugs (DMARDs)
Combining methotrexate with leflunomide or sulfasalazine increases myelosuppression and hepatotoxicity; monitoring blood counts and liver function is required.[1][2]
Hydroxychloroquine has minimal interaction but requires dose adjustments in renal impairment.[2]
Cancer Chemotherapy and Supportive Agents
In high-dose regimens, drugs like cisplatin or cyclosporine impair kidney function, delaying methotrexate clearance—leucovorin rescue is critical.[1]
Folic acid supplements reduce side effects without losing efficacy, but timing matters to avoid interference.[2]
How to Manage These Interactions
Check interactions via tools like Lexicomp or Drugs.com before starting therapy. Dose reductions, monitoring (e.g., weekly CBC, creatinine), or alternatives like switching NSAIDs to acetaminophen help mitigate risks.[1][3] Consult a pharmacist or use patient-specific apps for real-time alerts.
[1] Drugs.com - Methotrexate Interactions
[2] Medscape - Methotrexate Drug Interactions
[3] FDA Label - Methotrexate