Methotrexate Mercury Pharmaceuticals Ltd (Methotrexate Sodium)

Methotrexate is an antimetabolite used in the management of several autoimmune and oncologic conditions.

• Rheumatoid arthritis: reduces joint inflammation, pain and stiffness, and slows long‑term structural damage.
• Psoriasis: diminishes skin plaque formation, scaling and erythema, improving disease severity scores.
• Acute lymphoblastic leukemia: interferes with malignant lymphoblast proliferation, contributing to remission when used in induction regimens.
• Non‑Hodgkin lymphoma: suppresses tumor growth and enhances response to other chemotherapeutic agents in various lymphoma subtypes.
• Breast cancer: incorporated into adjuvant or neoadjuvant protocols to inhibit tumor cell replication and improve survival outcomes.

• Methotrexate inhibits the enzyme dihydrofolate reductase, preventing the conversion of dihydrofolate to tetrahydrofolate. This blockade reduces the cellular pool of tetrahydrofolate needed for synthesis of purine nucleotides and thymidylate, thereby impairing DNA, RNA and protein synthesis. The resulting antiproliferative effect is most pronounced in rapidly dividing cells, such as activated immune cells and malignant lymphocytes. Additionally, at higher concentrations, methotrexate may increase extracellular adenosine, contributing to its anti‑inflammatory properties.

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

Common Side Effects

• Nausea and vomiting
• Fatigue
• Mouth sores (stomatitis)
• Low white blood cell count (leukopenia)
• Elevated liver enzymes

Serious or Rare Side Effects

• Severe liver toxicity or fibrosis
• Pulmonary fibrosis or interstitial pneumonitis
• Bone marrow suppression leading to pancytopenia
• Renal impairment
• Rare severe skin reactions such as Stevens‑Johnson syndrome

When prescribing methotrexate, clinicians should observe several safety precautions to minimize toxicity.

• Baseline testing: obtain complete blood count, liver and renal function tests before initiation.
• Monitoring: repeat laboratory assessments regularly to detect hematologic or hepatic changes.
• Pregnancy contraindication: avoid use in women who are pregnant or may become pregnant; effective contraception is required.
• Drug interactions: review concomitant medications for potential additive toxicity, especially NSAIDs and penicillins.
• Patient education: advise patients to report signs of infection, persistent mouth ulcers, or unusual bruising promptly.
• Store at ambient temperature: keep tablets in the original container, protect from moisture and light, and store below 25 °C.

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

Major Interactions (Avoid)

• Non‑steroidal anti‑inflammatory drugs (NSAIDs): may increase methotrexate plasma levels and risk of renal toxicity.
• Proton pump inhibitors (e.g., omeprazole): can reduce renal clearance, heightening toxicity.
• High‑dose folic acid or folinic acid taken without medical supervision: may diminish therapeutic effect.

Moderate Interactions (Monitor Closely)

• Penicillins (e.g., ampicillin): may decrease methotrexate elimination, requiring dose adjustment.
• Sulfonamides: can potentiate bone marrow suppression.
• Live vaccines: immunosuppression may increase risk of infection; avoid during therapy.