Lewis Daniel H, Barfield Dominic M, Humm Karen R, Goggs Robert A
Department of Veterinary Clinical Sciences, Royal Veterinary College, Hawkshead Lane, North Mymms, Hertfordshire AL9 7TA, England.
J Am Vet Med Assoc. 2010 Dec 15;237(12):1450-4. doi: 10.2460/javma.237.12.1450.
2 English Pointers were suspected of having consumed toxic doses of methotrexate, a dihydrofolate reductase inhibitor frequently used in human and veterinary chemotherapeutic protocols.
Potentially toxic plasma concentrations of methotrexate were detected in both dogs. Results of physical examination, a CBC, blood gas analysis, and serum biochemical analysis were predominantly unremarkable, although 1 dog had mild hyponatremia (1372 mmol/L; reference range, 140 to 153 mmol/L) and mild hypocalcemia (1.03 mmol of ionized calcium/L; reference range, 1.13 to 1.33 mmol of ionized calcium/L).
Point-of-care determination of plasma methotrexate concentrations was not available; thus, palliative care was provided. Emesis was induced in both dogs by SC administration of apomorphine, and 3 doses of a suspension of activated charcoal with sorbitol were administered orally over a 6-hour period. Fluid diuresis was initiated in both dogs by administration of a compound sodium lactate solution, and N-acetylcysteine was administered IV to both dogs as a hepatoprotectant. A solution of calcium folinate (also known as leucovorin) was administered IV to both dogs to mitigate the effects of ingested methotrexate. No adverse effects associated with calcium folinate administration were identified, and no clinical or pathological evidence of methotrexate intoxication was detected.
IV administration of calcium folinate appeared to prevent the pathological sequelae of methotrexate intoxication without adverse effects. Administration of calcium folinate is recommended for the treatment of dogs with suspected or confirmed methotrexate overdose.
