Methotrexate Methotrexate 2mg/Ml Oral Solution (Methotrexate Disodium)

• Methotrexate is an antimetabolite used in several disease categories that involve abnormal cell proliferation or immune activation.
• Rheumatoid arthritis: reduces joint inflammation and slows structural damage, improving pain and functional ability.
• Psoriasis: decreases skin cell turnover and plaque formation, leading to clearer skin and symptom relief.
• Acute lymphoblastic leukemia: interferes with malignant lymphoblast proliferation, contributing to remission when used in chemotherapy protocols.
• Gestational trophoblastic disease: halts trophoblastic tissue growth, facilitating disease regression and preserving fertility when appropriate.

• Methotrexate inhibits dihydrofolate reductase, preventing conversion of dihydrofolate to tetrahydrofolate, a cofactor required for synthesis of purine nucleotides and thymidylate. This blockade reduces DNA, RNA and protein synthesis, particularly affecting rapidly dividing cells such as malignant lymphoblasts and activated immune cells, thereby exerting antineoplastic and immunosuppressive effects. The drug also accumulates polyglutamated forms inside cells, prolonging enzyme inhibition and enhancing cytotoxicity.

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

Common Side Effects

• Nausea or vomiting: gastrointestinal upset that may occur after dosing.
• Mouth ulcers: painful sores in the oral cavity.
• Fatigue: general tiredness or weakness.
• Transient liver enzyme elevation: mild increase in hepatic transaminases.

Serious or Rare Side Effects

• Bone marrow suppression: pancytopenia leading to infection, anemia or bleeding.
• Severe hepatotoxicity: significant liver injury, potentially progressing to fibrosis or cirrhosis.
• Pulmonary toxicity: interstitial pneumonitis or fibrosis causing respiratory symptoms.
• Renal impairment: reduced kidney function, especially with high doses or dehydration.

When prescribing methotrexate oral solution, clinicians should observe several safety measures.

• Baseline monitoring: obtain complete blood count, liver and renal function tests before initiation.
• Pregnancy risk: avoid use in pregnancy; effective contraception required for women of childbearing potential.
• Drug interactions: review concomitant medications that may increase toxicity, such as NSAIDs or penicillins.
• Dose adjustments: modify dose in patients with hepatic or renal impairment.
• Patient education: instruct patients to report signs of infection, mouth sores, or unusual bruising.
• Store at ambient temperature: keep below 25 °C, in original container, protected from moisture and light.

Methotrexate oral solution interacts with several agents that can alter its efficacy or toxicity.

Major Interactions (Avoid)

• Non‑steroidal anti‑inflammatory drugs (NSAIDs): increase risk of gastrointestinal toxicity and renal impairment.
• Proton pump inhibitors (e.g., omeprazole): may reduce renal clearance, raising methotrexate levels.
• Trimethoprim‑sulfamethoxazole: potentiates bone marrow suppression.
• Penicillins (e.g., ampicillin): can decrease renal clearance and raise toxicity.

Moderate Interactions (Monitor Closely)

• Azathioprine or other immunosuppressants: additive immunosuppression may increase infection risk.
• Live vaccines: reduced vaccine efficacy and potential for infection.
• High‑dose folic acid supplementation: may diminish therapeutic effect on disease activity.
• Phenytoin: may lower methotrexate plasma concentrations, reducing efficacy.