Peripheral markers of oxidative stress in Labrador retrievers with copper-associated hepatitis.

OBJECTIVES: To evaluate biomarkers of oxidative stress in dogs with copper-associated hepatitis (CAH) as compared with healthy controls, and to evaluate if these markers correlate with hepatic copper concentrations and hepatic histopathologic features. MATERIALS AND METHODS: Prospective study. Plasma reactive metabolite concentrations, plasma antioxidant potential, and plasma and urine isoprostane concentrations were determined in Labrador retrievers with copper-associated hepatitis (n=9) as well as in breed- and sex-matched (n=9) and age- and sex-matched (n=9) healthy control populations. Possible correlations between markers of oxidative stress and hepatic histopathological features also were investigated. RESULTS: Reactive metabolites (median, range) were over twofold greater in dogs with copper-associated hepatitis (87.2 RFU/µL, 60.9 to 185.6 RFU/µL) as compared to breed- and sex-matched (38.2 RFU/µL, 22.4 to 116.8 RFU/µL) and age- and sex-matched controls (32.0 RFU/µL, 18.5 to 127.4 RFU/µL). Antioxidant potential was decreased in copper-associated hepatitis dogs (6.5 TE/µL, 5.1 to 7.7 TE/µL) as compared to breed- and sex-matched controls (8.2 TE/µL, 5.3 to 11.8 TE/µL). Both reactive metabolite concentrations and the reactive metabolite to antioxidant potential ratio were positively correlated with hepatic copper concentrations. Plasma and urine isoprostanes were variable and not significantly different between populations. CLINICAL SIGNIFICANCE: Labrador retrievers with copper-associated hepatitis have altered oxidant status. Plasma reactive metabolite concentrations and the reactive metabolite to antioxidant potential ratio could be useful biomarkers. However, neither plasma nor urine isoprostanes were useful biomarkers for copper-associated hepatitis.

Pharmacokinetics and Relative Bioavailability of Orally Administered Innovator-Formulated Itraconazole Capsules and Solution in Healthy Dogs.

BACKGROUND: Itraconazole is commonly used for treatment of systemic and cutaneous mycoses in veterinary medicine. Two formulations, capsule and solution, are used interchangeably in dogs. However, marked differences in bioavailability have been reported in other species. Similar investigations have not been performed in dogs. OBJECTIVE: To determine and compare pharmacokinetics of itraconazole in dogs after oral administration of commercially available capsule and solution formulations intended for use in humans. ANIMALS: Eight healthy, adult, purpose-bred dogs. METHODS: Dogs received approximately 10 mg/kg of innovator-formulated itraconazole solution and capsule PO in randomized, crossover design with a 10-day washout period. To ensure maximal absorption, solution was administered to fasted dogs, whereas capsules were co-administered with food. Blood samples were collected at predetermined time points, and plasma drug concentrations were measured using high-pressure liquid chromatography. Pharmacokinetic parameters were determined with compartmental analysis. RESULTS: The mean relative bioavailability of the capsule was 85% that of the solution, but drug absorption was variable, and overall drug concentrations were similar between formulations. Mean elimination half-lives of both formulations were nearly identical at approximately 33 hours. Regardless of formulation, simulations suggest that a loading dose of 20 mg/kg, followed by 10 mg/kg once every 24 hours, will result in plasma concentrations considered to be adequate in most dogs. CONCLUSIONS AND CLINICAL IMPORTANCE: Contrary to findings reported in other species, overall drug exposures after capsule and solution administration are not substantially different in dogs. Despite some pharmacokinetic differences between itraconazole capsule and solution, formulation-specific dosages do not appear to be necessary.

Evaluation of Basal Serum or Plasma Cortisol Concentrations for the Diagnosis of Hypoadrenocorticism in Dogs.

BACKGROUND: Previous studies that included limited numbers of affected dogs have suggested basal cortisol concentrations ≤55 nmol/L (2 µg/dL) are sensitive, but nonspecific, for a diagnosis of hypoadrenocorticism. A detailed assessment of the diagnostic utility of basal cortisol concentrations is warranted. HYPOTHESIS/OBJECTIVES: To evaluate the utility of basal cortisol concentrations for the diagnosis of hypoadrenocorticism in a large number of dogs, including those with and without serum electrolyte abnormalities. ANIMALS: Five hundred and twenty-two dogs, including 163 dogs with hypoadrenocorticism, 351 dogs with nonadrenal gland illness, and 8 dogs with equivocal results. METHODS: Retrospective study. Basal and post-ACTH cortisol concentrations and sodium and potassium concentrations were collected from medical records. A receiver operating characteristic (ROC) curve was constructed for basal cortisol concentrations by standard methodologies. Sensitivity, specificity, and predictive values were determined for various cut-points. RESULTS: The area under the ROC curve was 0.988 and was similarly excellent regardless of serum electrolyte concentrations. At the most discriminatory cut-point of 22 nmol/L (0.8 µg/dL), sensitivity and specificity were 96.9 and 95.7%, respectively. A basal cortisol concentration of ≤55 nmol/L (2 µg/dL) resulted in a sensitivity of 99.4%. Conversely, a basal cortisol concentration of ≤5.5 nmol/L (0.19 µg/dL) resulted in a specificity of 99.1%. CONCLUSIONS AND CLINICAL IMPORTANCE: Similar to findings in previous studies, basal cortisol concentrations >55 nmol/L (2 µg/dL) are useful in excluding a diagnosis of hypoadrenocorticism. Interestingly, excellent specificities and positive predictive values were observed at lower cut-point cortisol concentrations.

Pharmacokinetics and relative bioavailability of D-penicillamine in fasted and nonfasted dogs.

BACKGROUND: D-Penicillamine is the most commonly used copper-chelating agent in the treatment of copper-associated hepatitis in dogs. Response to therapy can be variable, and there is a lack of pharmacokinetic information available for dogs. Coadministering the drug with food to alleviate vomiting has been recommended for dogs, which contradicts recommendations for drug administration to humans. HYPOTHESIS: Coadministration of d-penicillamine with food decreases relative bioavailability and maximum plasma drug concentrations (C(max)) in dogs. ANIMALS: Nine purpose-bred dogs with a median body weight of 17.0 kg. METHODS: Dogs received D-penicillamine (12.5 mg/kg PO) fasted and with food in a randomized, crossover design. Blood samples were collected before and 0.25, 0.5, 1, 2, 3, 4, 8, 12, and 24 hours after dosing. Total d-penicillamine concentrations were measured using liquid chromatography coupled with tandem quadrupole mass spectrometry. Pharmacokinetic parameters were calculated for each dog. RESULTS: Two fasted dogs (22%) vomited after receiving d-penicillamine. Mean C(max) ± standard deviation (SD) was 8.7 ± 3.1 µg/mL (fasted) and 1.9 ± 1.6 µg/mL (fed). Mean area under the plasma concentration curve ± SD was 16.9 ± 5.9 µg/mL·h (fasted) and 4.9 ± 3.4 µg/mL·h (fed). There were significant reductions in relative bioavailability and C(max) in fed dogs (P < .001). CONCLUSIONS AND CLINICAL IMPORTANCE: Coadministration of d-penicillamine with food significantly decreases plasma drug concentrations in dogs. Decreased drug exposure could result in decreased copper chelation efficacy, prolonged therapy, additional cost, and greater disease morbidity. Administration of d-penicillamine with food cannot be categorically recommended without additional studies.

Acquired proximal renal tubular dysfunction in 9 Labrador Retrievers with copper-associated hepatitis (2006-2012).

BACKGROUND: Copper-associated hepatitis (CAH) has been well described in Labrador Retrievers. However, the association of CAH with proximal renal tubular dysfunction in this breed has not been characterized. OBJECTIVES: To report clinical features, hepatic and renal histopathologic findings, tissue copper concentrations, and outcome of Labradors with CAH and proximal renal tubular disease. ANIMALS: Nine Labrador Retrievers with renal glucosuria and biopsy-confirmed CAH. METHODS: Clinical, clinicopathologic, and light microscopic findings were retrospectively reviewed. Rhodanine staining or atomic emission spectroscopy was performed on all hepatic samples and available renal tissue (4 dogs) to assess copper concentrations. RESULTS: Eight dogs had a history of polyuria and polydipsia, and all dogs had increased serum bilirubin concentrations. Five dogs had hyperchloremic metabolic acidosis. Three dogs with acidemia had paradoxical alkalinuria. All renal specimens had increased copper concentrations. Renal tubular vacuolization, degeneration, and regeneration were observed on light microscopy. Four dogs died within 10 days of diagnosis. One dog survived 2 months; 4 dogs survived more than 1 year. In long-term survivors, including 2 that did not undergo immediate copper chelation, resolution of renal tubular dysfunction occurred within weeks to months. CONCLUSIONS AND CLINICAL IMPORTANCE: Labrador Retrievers with CAH can develop clinical and laboratory evidence of renal tubular dysfunction in association with increased renal copper concentrations. Given the rarity of renal tubular disorders, detection of renal glucosuria and increased ALT activity in a Labrador Retriever is suggestive of CAH. Although renal tubular dysfunction may indicate advanced disease, successful long-term outcome is possible with a variety of therapies.