*Methotrexate*
#Formulations:
Methotrexate Tablets IP
Methotrexate injection IP
#Brand_Names : Neotrexate, Biotrexate
#Pharmacological_Action : This folic acid analogue is one of the oldest and highly efficacious antineoplastic drugs which acts by inhibiting dihydrofolate reductase, thus blocking the conversion of dihydrofolic acid to tetrahydrofolic acid. Utilizing the folate carrier it enters into cells and is transformed to more active polyglutamate from by the enzyme folypolyglutamate synthase. Tetrahydrofolic acid is an essential coenzyme required for one carbon transfer reactions in de novo purine synthesis and amino acid interconversion. The inhibition is pseudo irreversible because Mtx has 50000 times higher affinity for the enzyme than the normal substrate. It kills cells in S phase. In this process synthesis of RNA, DNA & protein suffers.
#special_effects: It is absorbed orally, 50% plasma protein bound, little metabolised and largely exerted unchanged in urine. Salicylates, sulfonamides, dicumerol, displace it from protein binding sites. Aspirin and sulfonamides enhance toxicity of Mtx by decreasing it's renal tubular secretion.
#Dose: 15-30 mg/day for 5 days orally or 20-40 mg/m² BSA i.m. or i.v. twice weekly.
#Side_Effects : High dose Mtx can induce remission in childhood acute lymphoblastic leukaemia and is also effective in maintenance of remission so that disease may cured.
#Therapeutic_Uses: antineoplastic drugs, immunosuppressant, rheumatoid arthritis