Pharmacokinetics of low-dose methotrexate in healthy beagle dogs

Intrathecal chemotherapy for the management of lymphoblastic lymphoma in a 4-year-old dog: a case report

Intrathecal chemotherapy is used in human medicine for the treatment or prophylaxis of CNS hematopoietic neoplasia. However, the clinical benefits in veterinary medicine have been scarcely documented. A 4-year-old male entire cross-breed dog presented with a 24-h history of severe lethargy, pelvic limb weakness, and urinary retention. Examination revealed generalized peripheral lymphadenomegaly, and the neurological findings were suggestive of a myelopathy in the region of T3-L3. Following the diagnosis of multicentric lymphoblastic B-cell lymphoma (stage Vb), a modified L-LOP with cytosine arabinoside was started, and complete clinical remission was achieved. After 4 weeks, there was acute neurological deterioration (spinal pain and proprioceptive deficits) without peripheral lymphadenomegaly. MRI findings and CSF analysis were consistent with meningeal and spinal cord lymphoma infiltration at the level of L3. Intrathecal chemotherapy (cytosine arabinoside and methotrexate) were administered in the cisterna magna with systemic dexamethasone and analgesia. Clinical signs were resolved within 24 h, and the patient remained asymptomatic for 3.5 weeks. After this period, CNS relapse (proprioceptive deficits and severe thoracolumbar pain) was suspected, and repeat intrathecal chemotherapy was declined. The patient was humanely euthanized 9 weeks after the initial diagnosis. This is the first report on the clinical benefit of intrathecal chemotherapy with a combination of methotrexate and cytarabine for the management of CNS lymphoma in dogs. Based on our case, intrathecal chemotherapy with methotrexate and cytarabine can induce a short-lasting CNS clinical remission (3 weeks).

Pharmacokinetics of low-dose methotrexate in horses

This study aimed to investigate both the pharmacokinetic behavior and tolerance of methotrexate (MTX) in horses to design a specific dosing regimen as a new immunomodulatory drug for long-term treatment. To determine the primary plasma pharmacokinetic variables after single intravenous, subcutaneous or oral administration, six horses were administered 0.3 mg/kg MTX in a crossover design study. After a 10-week washout, MTX was administered subcutaneously to three of the six previously treated horses at a dose of 0.3 mg/kg once per week for 3 months. In both studies, MTX and metabolite concentrations were measured using LC-MS/MS. The absolute bioavailability of MTX was 73% following subcutaneous administration but less than 1% following oral administration. The plasma clearance was 1.54 ml min^-1  kg^-1 (extraction ratio = 2%). After 24 hr, plasma concentrations were below the LOQ. No adverse effects were noted except for a moderate reversible elevation in liver enzymes (GLDH). With regards to the main metabolites of MTX, very low concentrations of 7-hydroxy-MTX were found, whereas polyglutamated forms (mainly short chains) were found in red blood cells. A subcutaneous dose of 0.2 mg kg^-1  week^-1 may be safe and relevant in horses, although this has yet to be clinically confirmed.

Granulomatous mural folliculitis in a dog treated with ciclosporin and methotrexate

BACKGROUND

Canine granulomatous mural folliculitis is a very rare cause of scarring alopecia with unknown pathogenesis.

HYPOTHESIS/OBJECTIVES

To report a case of granulomatous mural folliculitis in a dog treated with ciclosporin (Cs) and methotrexate (MTX).

ANIMAL

A 13-year-old spayed female Pyrenean shepherd dog with a one month history of scarring alopecia.

METHODS AND RESULTS

Histopathological examination revealed a granulomatous and lymphocytic mural and necrotizing folliculitis and furunculosis. Immunochemistry, using antibodies for CD3, CD204, CD206, IBA-1 and CD208, revealed that CD3⁺ lymphocytes were infiltrating the outer root sheath along with IBA-1⁺ or CD204⁺ cells. Ciclosporin (5 mg/kg once daily) and MTX (0.25 mg/kg once weekly then 0.5 mg/kg once weekly) were initiated simultaneously, and Cs was stopped after stabilization of the lesions. The dog's skin disease was stable for six months.

CONCLUSIONS AND CLINICAL IMPORTANCE

To the best of the authors' knowledge, this is the first report of the long-term management of a granulomatous mural folliculitis in a dog. Ciclosporin and MTX appeared to be an effective treatment option. Additional treated cases are needed to assess the effectiveness of MTX in canine immune-mediated diseases.