belongs to the anti-metabolite category of medications and is indicated for the treatment of certain neoplastic diseases like osteosarcoma and lymphoma apart from rheumatoid arthritis. On administration, Methotrexate gets involved with DNA synthesis and cellular replication thereby controlling unrestricted multiplication of cancerous cells.
Precautions Be cautious while administering Methotrexate in animals with confirmed hypersensitivity to the medicine, or in those with conditions like bone marrow suppression, hepatic or renal failures etc. Abstain from administering this medication in pregnant animals. Do not use Methotrexate along with NSAIDs and drugs containing compounds of salicylates, phenylbutazone etc, which could dislodge methotrexate from albumin binding sites, thereby increasing its toxicity. Discuss with the vet the medications the pet is taking as many a medicine such as folic acid or Penicillins could increase the toxicity of Methotrexate, apart from bringing out increased bone marrow suppression and other complications. Conduct regular blood tests to ensure a healthy blood count and if at any point of time, the white blood cell count falls below 4000/mm3 or platelets fall below 100,000/mm3, stop the treatment forthwith and bring the matter to the attention of the veterinarian.
Dosage Methotrexate injection can be administered intramuscularly or intravenously and is available in 50, 100, 200, and 250 mg single-dose vials. Very often it is used as part of multi drug therapy and the dosages might differ according to the complementary drugs. Never double the dose to compensate any missed doses. The normal dose for dogs is 2.5 mg/m2 PO daily; and 20 mg/m2 IV weekly.