• Choriocarcinoma: 15-30 mg daily for 5 days, repeat after an interval of ?1 wk for 3-5 courses.
• Acute lymphoblastic leukaemia: Maintenance: 15 mg/m2 once or twice wkly, with other agents.
• Burkitt’s lymphoma: 10-25 mg daily for 4-8 days, repeated after 7-10 days.
• Psoriasis: 10-25 mg wkly as a single dose, adjust subsequent doses based on response.
• Rheumatoid arthritis: 7.5 mg once wkly, adjust by response. Not more than 20 mg/wk.
• Mycosis fungoides: 2.5-10 mg daily to induce remission.
• Crohn’s disease: 12.5-22.5 mg once wkly for up to 1 yr.

Parenteral-

• Psoriasis: 10-25 mg wkly as a single dose. Adjust subsequent doses based on response. May be given via IV/IM admin.

Intramuscular-

• Choriocarcinoma: 15-30 mg daily for 5 days. Repeat after at least 1 wk for 3-5 courses. Alternatively, 0.25-1 mg/kg (max: 60 mg) every 48 hr for 4 doses followed by folinic acid rescue, repeat at intervals of 7 days for 4 or more courses.
• Mycosis fungoides: 50 mg wkly as a single dose or 2 divided doses.
• Acute lymphoblastic leukaemia: Maintenance: 15 mg/m² once or twice wkly, with other agents.
• Crohn’s disease: 25 mg once wkly for 16 wk. Maintenance: 15 mg wkly.

Intrathecal-

• Meningeal leukaemia: 12 mg/m² (max 15 mg) once wkly for 2-3 wk, then once mthly. Alternatively, 200-500 mcg/kg every 2-5 day until CSF cell count is normalised.

Intravenous-

• Osteosarcoma: Initial recommended dose: 12 g/m² as a 4-hr infusion, followed by folinic acid, as part of combined therapy. May increase dose to 15 g/m² in subsequent treatments if initial dosage is insufficient to achieve peak serum methotrexate levels of 454 mcg/mL at the end of the infusion. Methotrexate infusion is administered on postoperative wk 4, 5, 6, 7, 11, 12, 15, 16, 29, 30, 44 and 45; in combination with other chemotherapy agents. Folinic acid can be given orally, IM or IV inj starting 24 hr after the beginning of the methotrexate infusion. Give via parenteral routes If patient experiences GI toxicity (e.g., nausea, vomiting). Usual dosage of folinic acid: 15 mg every 6 hr for a total of 60 hr or a total of 10 doses.
• Breast cancer: 10-60 mg/m² often with cyclophosphamide and fluorouracil.
• Advanced lymphosarcoma: Up to 30 mg/kg, followed by folinic acid rescue.
• Acute lymphoblastic leukaemia: Maintenance: 2.5 mg/kg every 14 days.