Methotrexate Orion Pharma (Methotrexate)

Methotrexate is used in several disease categories where inhibition of folate metabolism is therapeutic.

• Rheumatoid arthritis: reduces joint inflammation and slows disease progression.
• Psoriasis: decreases skin cell proliferation and improves plaque lesions.
• Acute lymphoblastic leukemia: interferes with malignant cell replication as part of chemotherapy protocols.
• Non‑Hodgkin lymphoma: contributes to tumor control in combination regimens.
• Osteosarcoma: used as part of multi‑agent chemotherapy to inhibit tumor growth.

• Methotrexate inhibits dihydrofolate reductase, blocking the conversion of dihydrofolate to tetrahydrofolate. This reduces folate‑dependent synthesis of purine nucleotides and thymidylate, impairing DNA replication and cell division, particularly in rapidly proliferating tissues such as immune cells and malignant cells.

Methotrexate may cause a range of adverse reactions, varying from mild to severe.

Common Side Effects

• Nausea: mild to moderate gastrointestinal upset.
• Fatigue: general tiredness.
• Mouth sores: oral mucositis.
• Elevated liver enzymes: mild hepatic irritation.
• Low blood counts: mild leukopenia or anemia.

Serious or Rare Side Effects

• Severe liver toxicity: potential hepatitis or fibrosis.
• Pulmonary toxicity: interstitial pneumonitis.
• Bone marrow suppression: severe pancytopenia.
• Renal impairment: reduced kidney function.
• Severe skin reactions: Stevens‑Johnson syndrome.

Before initiating therapy, clinicians should assess baseline organ function and counsel patients on risk mitigation.

• Monitor liver function: perform baseline and periodic liver enzyme tests.
• Assess blood counts: regular CBC to detect cytopenias.
• Evaluate renal function: adjust use if creatinine clearance is reduced.
• Avoid use in pregnancy: contraindicated due to teratogenic risk.
• Counsel on contraception: ensure effective birth control during treatment and for several months after cessation.
• Store at ambient temperature: keep below 25°C in original packaging, protect from moisture and light.

Methotrexate interacts with several drug classes that can alter its safety or efficacy.

Major Interactions (Avoid)

• Non‑steroidal anti‑inflammatory drugs (NSAIDs): increase risk of renal toxicity.
• Proton pump inhibitors: may elevate methotrexate serum levels.
• Trimethoprim‑sulfamethoxazole: potentiates bone marrow suppression.
• Live vaccines: risk of infection due to immunosuppression.

Moderate Interactions (Monitor Closely)

• Penicillins: may reduce renal clearance of methotrexate.
• Sulfonylureas: enhanced hypoglycemic effect.
• Anticonvulsants (e.g., phenytoin): may alter folate metabolism.