To describe the clinical presentation, treatment, and treatment outcomes for companion rats (Rattus norvegicus) diagnosed with lymphoma.
All rats that presented to the exotics service and underwent postmortem examination during the time period of 2008 through 2020 were evaluated.
The medical records of 35 rats were evaluated for an ante- or postmortem diagnosis of lymphoma. Cases with a diagnosis of lymphoma were further reviewed for signalment, presenting complaint, clinical signs observed on physical exam, diagnostic testing performed, and treatments administered. Postmortem gross and histologic findings were reviewed.
7 out of 35 rats were diagnosed with lymphoma, either ante-mortem or postmortem. The most common presenting complaint that was present in all rats with lymphoma was respiratory abnormalities. Five out of 7 rats had radiographs performed, all of which had abnormalities noted in the thoracic cavity including pulmonary nodules, cranial mediastinal widening, or alteration to the cardiac silhouette. Diagnosis via cytologic aspirates was performed in 2 cases and each was diagnostic for lymphoma; however, even with treatment, survival time following initiation of chemotherapy was short (less than or equal to 24 days). The definitive diagnosis in the remainder of the cases was via necropsy.
Results suggest that lymphoma is a common neoplastic disease in rats and a thorough diagnostic work-up is indicated in any rat that presents for general malaise or respiratory signs.
To examine the pharmacokinetics and ex vivo pharmacodynamics of oral firocoxib administration in New Zealand White rabbits (Oryctolagus cuniculus).
6 healthy New Zealand White rabbits.
Pharmacokinetics were determined from plasma concentrations measured via ultra performance liquid chromatography-tandem mass spectrometry after oral administration of firocoxib at a dose of 3.74 to 4.20 mg/kg. Pharmacokinetic analysis was performed using non compartmental methods. Pharmacodynamics of firocoxib were evaluated by measuring plasma concentrations of thromboxane and prostaglandin via ELISAs as surrogate markers of cyclooxygenase enzyme isoform inhibition.
The terminal rate constant was 0.07 hours (range, 0.05 to 0.11 h). The mean maximum concentration (Cmax) and time to Cmax were 0.16 µg/mL and 3.81 hours (range, 2.0 to 8.0 h), respectively. Mean residence time was 15.02 hours. Mean elimination half-life was 9.12 hours. For the pharmacodynamic analysis, firocoxib administration did not demonstrate a significant difference between any time point for prostaglandin E2 and only a significant difference between 24 and 48 hours for thromboxane B2.
Although the pharmacokinetic research supports that plasma firocoxib concentrations that would be therapeutic in dogs are achieved in rabbits, the pharmacodynamic results do not demonstrate a significant difference in levels of cyclooxygenase-2 inhibition, which indirectly reflects the anti-inflammatory effects of the drug. Further pharmacodynamic studies and multidose studies are warranted to determine the efficacy and safety of this drug in rabbits.