Methotrexate is an antimetabolite anticancer and immunosuppressive drug.
It acts by inhibiting dihydrofolate reductase, leading to suppression of DNA, RNA, and protein synthesis—especially in rapidly dividing cells.
The 500 mg strength is generally used in moderate- to high-dose chemotherapy regimens and is administered only under specialist supervision.

Oncology (Cancer Treatment)

• Acute lymphoblastic leukemia (ALL)

• Non-Hodgkin’s lymphoma

• Osteosarcoma (high-dose methotrexate protocols)

• Breast cancer

• Head and neck cancers

• Choriocarcinoma / Gestational trophoblastic neoplasia

• Lung cancer (as part of combination chemotherapy)

Common Side Effects

• Nausea and vomiting

• Mouth ulcers (stomatitis)

• Loss of appetite

• Fatigue

• Hair thinning

• Injection-site reactions

Serious Side Effects

• Bone marrow suppression

  • Leukopenia (infection risk)

  • Thrombocytopenia (bleeding)

  • Anemia

• Liver toxicity (elevated enzymes, fibrosis)

• Kidney toxicity (especially high-dose therapy)

• Pulmonary toxicity (methotrexate pneumonitis)

• Severe skin reactions

• Neurotoxicity (especially with intrathecal use)

Dosage varies widely and must be prescribed by an oncologist or specialist.

Cancer Chemotherapy (Examples)

• Moderate dose:

  • 50–500 mg/m² IV, depending on protocol

• High-dose therapy (e.g., osteosarcoma):

  • 1–12 g/m² IV infusion

  • Requires leucovorin rescue, urine alkalinization, and intensive monitoring