Namaxir (Methotrexate)

Methotrexate is used in several inflammatory joint disorders, acting to reduce immune‑mediated damage.

• Rheumatoid arthritis: reduces joint inflammation, pain, and slows structural damage.
• Psoriatic arthritis: alleviates joint symptoms and prevents progression of joint erosion.
• Osteoarthritis pain (inflammatory component): provides symptomatic relief of pain and swelling.
• Other inflammatory joint conditions: manages pain and inflammation where standard therapies are insufficient.
• Juvenile idiopathic arthritis: helps control disease activity and improve joint function in children.
• Severe plaque psoriasis: decreases skin lesion severity when administered systemically.

• Methotrexate inhibits the enzyme dihydrofolate reductase, blocking the conversion of dihydrofolate to tetrahydrofolate. This interruption impairs synthesis of purine nucleotides and thymidylate, leading to reduced DNA replication and cell proliferation. In immune cells, the resulting antiproliferative effect diminishes the production of inflammatory cytokines, thereby exerting immunosuppressive and anti‑inflammatory actions.

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

Common Side Effects

• Nausea and vomiting.
• Fatigue or general weakness.
• Mouth sores (stomatitis).
• Elevated liver enzymes.
• Decreased blood cell counts.
• Headache.

Serious or Rare Side Effects

• Severe liver toxicity or fibrosis.
• Pulmonary fibrosis or interstitial pneumonitis.
• Significant bone marrow suppression leading to pancytopenia.
• Acute renal impairment.
• Anaphylactic or severe hypersensitivity reactions.
• Opportunistic infections due to immunosuppression.

When using methotrexate, careful monitoring and specific precautions are essential.

• Monitor liver function: perform baseline and periodic liver enzyme tests.
• Assess renal function: adjust dosing if renal impairment is present.
• Evaluate blood counts: conduct regular complete blood count monitoring.
• Avoid in pregnancy: drug is teratogenic and contraindicated (Category X).
• Review concomitant medications: NSAIDs and other folate antagonists may increase toxicity.
• Store at 2-8°C: keep refrigerated, protect from light, do not freeze or shake.

Methotrexate interacts with several drug classes; awareness of major and moderate interactions helps prevent adverse events.

Major Interactions (Avoid)

• Non‑steroidal anti‑inflammatory drugs (NSAIDs): increase risk of renal toxicity.
• Live vaccines: heightened risk of severe infection.
• Other folate antagonists (e.g., aminopterin): additive toxicity.
• High‑dose penicillins: may raise methotrexate plasma levels.
• Trimethoprim‑sulfamethoxazole: enhances myelosuppression.

Moderate Interactions (Monitor Closely)

• Proton pump inhibitors: may affect methotrexate absorption.
• Sulfonamides: increase risk of hematologic toxicity.
• Azathioprine: additive immunosuppressive effect.
• Phenytoin: may alter methotrexate clearance.
• Alcohol: can exacerbate liver toxicity.