Methotrexate is an antimetabolite chemotherapy drug.
This drug competitively inhibits dihydrofolic acid reductase, which is normally reduced to tetrahydrofolates in purine nucleotide and thymidine synthesis. Thus, methotrexate interferes with DNA synthesis, repair, and cellular replication.
The main side-effects of this drug are vomiting, diarrhea and bone marrow suppression characterized by leucopenia, and in some dogs, a protein-losing enteropathy may ensue, requiring special attention.
Recommended dose is 2.5 mg/m2 orally once daily or 5.0 mg/m2 orally on days 1 and 5 of a biweekly maintenance schedule.
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