Methotrexate

Category: pharmacological

Aliases: MTX, Trexall, Otrexup

Pharmacological Mechanism

Folate antagonist — inhibits DHFR → reduces tetrahydrofolate → impairs thymidine + purine synthesis. Low-dose immunosuppressive mechanism is AICAR accumulation → adenosine release → anti-inflammatory. Leucovorin (folinic acid) is the antidote for overdose.

Half-Life (t½)

PO: 8h, IV: 8h

Dosing Guidelines

• PO: Typical 13.3mg (Range: 7.5 - 25 mg)
• SC: Typical 13.3mg (Range: 7.5 - 25 mg)
• IM: Typical 13.3mg (Range: 7.5 - 25 mg)
• IV: Typical 13.3mg (Range: 7.5 - 25 mg)

Target Organ Systems

• immune-hematologic

Interactions

• Folic Acid