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Methotrexate
- indication:For the treatment of gestational choriocarcinoma, chorioadenoma destruens and hydatidiform mole. Also for the treatment of severe psoriasis and severe, active, classical or definite rheumatoid arthritis.
- pharmacologypharmacology:
- mechanism: Methotrexate anti-tumor activity is a result of the inhibition of folic acid reductase, leading to inhibition of DNA synthesis and inhibition of cellular replication. The mechanism involved in its activity against rheumatoid arthritis is not known.
- toxicity: Symptoms of overdose include bone marrow suppression and gastrointestinal toxicity. LD<sub>50</sub>=43mg/kg(orally in rat).
- absorprion: Generally well absorbed with a mean bioavailability of about 60%.
- halflife: Low doses: 3 to 10 hours; High doses: 8 to 15 hours.
- roouteelimination: With IV administration, 80% to 90% of the administered dose is excreted unchanged in the urine within 24 hours. There is limited biliary excretion amounting to 10% or less of the administered dose.
- volumedistribution: * 0.4 to 0.8 L/kg
- clearance: