Mtx Ratiopharm (Methotrexate)

Methotrexate is a folate antagonist used across several disease families, particularly inflammatory and oncologic conditions.

• Rheumatoid arthritis: reduces disease activity and slows joint damage.
• Psoriasis: improves severe skin lesions and reduces plaque formation.
• Acute lymphoblastic leukemia: contributes to remission by inhibiting malignant cell proliferation.
• Non‑Hodgkin lymphoma: used in combination regimens to control tumor growth.
• Ectopic pregnancy: provides medical management to terminate non‑viable implantation.

• Methotrexate inhibits the enzyme dihydrofolate reductase, decreasing tetrahydrofolate synthesis. This limits the availability of one‑carbon units required for purine and pyrimidine synthesis, impairing DNA, RNA and protein production in rapidly dividing cells. The drug also modulates immune function by increasing extracellular adenosine, which exerts anti‑inflammatory effects.

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

Common Side Effects

• Nausea and vomiting
• Fatigue or malaise
• Oral mucosal ulceration (stomatitis)
• Mild liver enzyme elevation
• Transient low blood cell counts
• Alopecia (hair thinning)

Serious or Rare Side Effects

• Severe bone‑marrow suppression leading to pancytopenia
• Pulmonary toxicity (interstitial pneumonitis)
• Significant hepatotoxicity or fibrosis
• Life‑threatening infections due to immunosuppression
• Renal impairment or failure
• Anaphylactic or severe hypersensitivity reactions

Methotrexate requires careful monitoring and specific safety measures.

• Pregnancy contraindication: teratogenic; avoid use in pregnant or planning patients.
• Monitor blood counts: regular CBC to detect marrow suppression.
• Liver function: periodic LFTs to assess hepatotoxicity.
• Renal function: adjust dosing if renal impairment is present.
• Folate supplementation: consider to reduce mucosal and hematologic toxicity.
• Store at 2-8°C: keep refrigerated, protect from light, do not freeze or shake.

Methotrexate interacts with several drugs that can alter its efficacy or toxicity.

Major Interactions (Avoid)

• NSAIDs: increase methotrexate serum levels and risk of toxicity.
• Penicillins (e.g., ampicillin): potentiate myelosuppression.
• Live vaccines: heightened risk of infection due to immunosuppression.
• Other folate antagonists (e.g., trimethoprim): additive hematologic toxicity.

Moderate Interactions (Monitor Closely)

• Azathioprine: combined immunosuppression may require dose adjustments.
• Sulfasalazine: may increase methotrexate toxicity.
• Allopurinol: can raise methotrexate levels, monitor renal function.
• Warfarin: methotrexate may enhance anticoagulant effect, monitor INR.