Methotrexat Medac (Methotrexate Disodium)

Methotrexate is employed in several autoimmune and oncologic conditions where inhibition of rapidly dividing cells is therapeutic.

• Rheumatoid arthritis: reduces joint inflammation and slows disease progression.
• Psoriasis: decreases skin cell proliferation, improving plaque severity.
• Acute lymphoblastic leukemia: interferes with leukemic cell replication, contributing to remission.
• Non‑Hodgkin lymphoma: impedes malignant lymphocyte growth as part of combination chemotherapy.
• Osteosarcoma: limits tumor cell division, used in multimodal treatment protocols.

• Methotrexate inhibits the enzyme dihydrofolate reductase, preventing the conversion of dihydrofolate to tetrahydrofolate, a cofactor required for synthesis of purine nucleotides and thymidylate. This blockade reduces DNA, RNA and protein synthesis, leading to decreased proliferation of rapidly dividing cells such as immune‑mediated inflammatory cells and malignant tumor cells. Additionally, at higher concentrations, methotrexate can inhibit enzymes involved in purine metabolism, further enhancing its cytotoxic effect.

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

Common Side Effects

• Nausea and vomiting
• Mucositis (mouth sores)
• Fatigue
• Elevated liver enzymes

Serious or Rare Side Effects

• Bone marrow suppression leading to anemia or infection
• Pulmonary toxicity, including interstitial pneumonitis
• Severe hepatotoxicity or fibrosis
• Nephrotoxicity with renal impairment

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

• Monitor blood counts: perform regular complete blood count tests to detect marrow suppression.
• Assess liver function: conduct periodic liver enzyme tests and adjust therapy if elevations occur.
• Evaluate renal function: check serum creatinine and adjust dose in renal impairment.
• Avoid pregnancy: contraindicated in pregnancy; effective contraception required for both sexes.
• Review concomitant medications: NSAIDs, penicillins and sulfonamides can increase toxicity.
• Store below 25°C: keep in the original container, protect from moisture and light.

Methotrexate has notable drug interactions that may require dose adjustment or avoidance.

Major Interactions (Avoid)

• NSAIDs (e.g., ibuprofen, naproxen): increase methotrexate plasma levels and risk of toxicity.
• Penicillins (e.g., ampicillin): reduce renal clearance, heightening toxicity.
• Sulfonamides and trimethoprim: potentiate myelosuppression.
• Proton pump inhibitors: may elevate methotrexate concentrations.

Moderate Interactions (Monitor Closely)

• Oral contraceptives: reduced efficacy, consider alternative birth control.
• Allopurinol: may increase methotrexate toxicity; monitor closely.
• Folic acid supplements: can lessen efficacy but improve tolerance; adjust dose as needed.
• Azathioprine or other immunosuppressants: additive immunosuppression, monitor infection risk.