Doses - METHOTREXATE, METHOTREXATE SODIUM
Dogs:For susceptible neoplastic diseases (usually as part of a multi-drug protocol):
a) 2.5 mg/m2 PO daily (Rosenthal 1985)
b) For malignant lymphoma: 5 mg/m2 on days 1 and 5 of a weekly maintenance schedule.(Coppoc 1988)
c) 2.5 mg/m2 PO 2-3 times weekly; 0.3 - 0.8 mg/m2 IV every 7 days. (O'Keefe and Harris1990)
d) "High dose therapy": 5 - 10 mg/m2 PO, IV, IM or intrathecally followed 2-4 hourslater with leucovorin at 3 mg/m2."Normal dose therapy": 2.5 mg/m2 once daily. Adjust dosage/frequency according totoxicity. (Thompson 1989a)
e) For lymphoma (as part of protocol¯see reference): 0.5 mg/kg IV (maximum dose 25mg) on day 14. (Matus 1989)
f) 2.5 mg/m2 PO daily. (MacEwen and Rosenthal 1989)
g) In combination with other antineoplastics (per protocol) 5 mg/m2 PO twice weekly or0.8 mg/kg IV every 21 days; alternatively 2.5 mg/m2 PO daily. (USPC 1990)
Cats:For susceptible neoplastic diseases (usually as part of a multi-drug protocol):
a) 2.5 mg/m2 PO 2-3 times weekly; 0.3 - 0.8 mg/m2 IV every 7 days. (O'Keefe and Harris1990)
b) For lymphoma (as part of protocol¯see reference): 0.8 mg/kg IV on day 14 with 5 mgprednisone bid PO. (Matus 1989)
c) For lymphosarcoma: 2.5 - 5 mg/m2 PO 2 - 3 times per week.
For carcinomas and some sarcomas: 10 - 15 mg/m2 every 1-3 weeks. (Couto 1989b)
d) In combination with other antineoplastics (per protocol) 5 mg/m2 PO twice weekly.(USPC 1990)
Monitoring Parameters - 1. Efficacy; 2. Toxicity: a) Monitor for clinical signs and symptoms of
GI irritation and ulceration. b) Complete blood counts (with platelets) should be performed weeklyearly in therapy and eventually every 4-6 weeks when stabilized. If WBC is < 4000/mm3 or plateletcount is <100, 000/mm3 therapy should be discontinued. c) Baseline renal function tests. Continueto monitor if abnormal. d) Baseline hepatic function tests. Monitor liver enzymes on a regular basisduring therapy.
Client Information - Clients must be briefed on the possibilities of severe toxicity developingfrom this drug, including drug-related mortality. Clients should contact the veterinarian should thepatient exhibit any symptoms of profound depression, abnormal bleeding (including bloodydiarrhea) and/or bruising. Wear gloves when administering tablets (particularly if crushed or split); if gloves are not used, wash hands thoroughly after handling tablets.
Dosage Forms/Preparations/FDA Approval Status/Withholding Times - Veterinary-Approved Products: None
Human-Approved Products:Methotrexate Sodium Oral Tablets (scored) 2.5 mg; Methotrexate® (Immunex), Rheumatrex® &
Rheumatrex Dose Pack® (Lederle) (Rx)
Methotrexate Sodium Injection 2.5 mg/ml in 2 ml vials and 25 mg/ml in 2, 4, 8, & 10 ml vials;
Methotrexate (Lederle), generic; (Rx). Also available in preservative-free 25 mg/ml formulations: Folex®PFS (Adria), Methotrexate LPF® (Lederle); (Rx)
Methotrexate Powder for Injection in 20 mg/vial, 50 mg/vial, and 1 g vials for reconstitution; (Rx)