Methotrexate
Administration
- Type: Immunosuppressant/antineoplastic
- Dosage Forms:
- Routes of Administration: IV/IM, oral
- Common Trade Names:
Adult Dosing
- Ectopic pregnancy:
Single-dose regimen: Methotrexate 50 mg/m2 on day 1; Measure serum hCG levels on days 4 and 7; if needed, repeat dose on day 7 (Barnhart 2009) Two-dose regimen: Methotrexate 50 mg/m2 on day 1; Measure serum hCG levels on day 4 and administer a second dose of methotrexate 50 mg/m2; Measure serum hCG levels on day 7 and if needed, administer a third dose of 50 mg/m2 (Barnhart 2009)
- Doses for treatment of malignancy or autoimmune diseases vary widely
Pediatric Dosing
Special Populations
- Pregnancy Rating: X
- Lactation risk: Infant risk has been determined (risk of serious adverse effects for infant)
Renal Dosing
- Adult:
- Pediatric:
Hepatic Dosing
- Adult:
- Pediatric:
Contraindications
- Allergy to class/drug
- Breastfeeding, pregnant, or possibility of impregnating someone
- Blood dyscrasias
- Chronic liver disease
Adverse Reactions
Serious
- Hepatotoxicity
- Nephrotoxicity
- Myelosuppression, aplastic anemia, pancytopenia
- Infectious disease
- Tumor lysis syndrome
- GI bleed
- Neurotoxicity, seizure
- Pericardial effusion
- TEN
Common
- Nausea/vomiting, diarrhea
- Stomatitis
- Leukopenia, thrombocytopenia
- Alopecia, photosensitivity, rash
- Dizziness
Pharmacology
- Half-life: 8-15hr
- Metabolism: Extensive hepatic and intracellular
- Excretion: Mostly renal. Dialyzable.
Mechanism of Action
- Inhibits dihydrofolate reductase--> blocks DNA synthesis and thus, cellular replication/repair