Prednisolone in Dogs-Plasma Exposure and White Blood Cell Response

Pharmacology of drugs used in autoimmune dermatopathies in cats and dogs: A narrative review

Immunosuppressive drugs are the mainstay of treatment for many feline and canine autoimmune skin diseases, either as monotherapy or in combination with other drugs. Treatment with these drugs is often lifelong and may have long-term consequences on the affected animal's overall quality-of-life. Clinicians need to understand the pharmacology of immunosuppressants in planning and executing the treatment regimen for the best possible clinical outcome, as well as reducing the risk of adverse effects. This review paper will focus on the mechanism of action, pharmacokinetics and pharmacodynamics, clinical uses and adverse effects of immunosuppressive drugs used to treat autoimmune dermatoses in cats and dogs. These include glucocorticoids, ciclosporin A, azathioprine, chlorambucil, mycophenolate mofetil, oclacitinib and Bruton's tyrosine kinase inhibitors.

Retrospective evaluation of the effect of acid suppressant drugs on leukocyte ratios in dogs with mast cell tumors

BACKGROUND

Acid suppressant drugs (ASDs) are commonly used to decrease gastric acid production, but some evidence exists that ASDs exert immunomodulatory effects. Such an effect has not been investigated in dogs for which ASDs are routinely prescribed.

HYPOTHESIS

Compared to naïve subjects, dogs treated with ASDs will exhibit differences in leukocyte ratios after treatment.

ANIMALS

Fifty-one dogs with mast cell tumors (MCTs).

MATERIALS AND METHODS

Dogs with MCT that were either AS naïve or treated with ASDs (i.e., histamine-2-receptor antagonists [H2RA] or proton pump inhibitors [PPI]) were included in this retrospective study. Subjects were categorized into 3 treatment groups (AS naïve, H2RA treated, and PPI treated), and leukocyte ratios (neutrophil:eosinophil, lymphocyte:monocyte, and neutrophil:lymphocyte [NLR]) were calculated before and after treatment. A mixed effects analysis of variance on ranks was used to assess differences in ratios between treatments, between pre- and post-treatment time points, and between pre- and post-time points for each treatment. Concurrent administration of antihistamines, corticosteroids, and chemotherapeutic drugs was assessed as a confounding factor.

RESULTS

Famotidine (n = 14/14) and omeprazole (n = 12/12) were the only H2RA and PPI used, respectively. Dogs receiving famotidine had a significant increase in median NLR from pre- to post-treatment (3.429; range, 1.417-15 to 5.631; range, 2.654-92; P < 0.01) compared to PPI treated or AS naïve dogs. No differences existed in chemotherapeutic drug or corticosteroid use between groups.

CONCLUSIONS

A significant difference in NLR was identified in famotidine treated dogs compared with omeprazole treated or AS naïve dogs.

Vincristine-induced adverse events related to body weight in dogs treated for lymphoma

BACKGROUND

Traditional dosing of chemotherapy drugs based on body surface area may overdose small dogs, leading to an increased frequency of adverse events (AEs).

HYPOTHESIS/OBJECTIVES

Evaluate the frequency of hematologic and gastrointestinal AEs in dogs with newly diagnosed lymphoma treated with vincristine weighing ≤15 kg in comparison to dogs weighing >15 kg. We hypothesized that dogs weighing ≤15 kg would experience a higher frequency of AEs.

ANIMALS

One hundred and thirty-eight dogs with newly diagnosed lymphoma were treated with vincristine.

METHODS

A multicenter retrospective study reviewing hematologic data and medical record information. Complete blood counts were performed no more than 24 hours before vincristine administration and then between 4 and 8 days post-administration. Data were evaluated using logistic regression or ordinal logistic regression.

RESULTS

Thirty-eight dogs weighing ≤15 kg and 100 dogs weighing >15 kg were included. The median vincristine dose for both groups was 0.6 mg/m2. Seventeen (12.3%) instances of neutropenia occurred with no significant difference in overall frequency or grade between groups. Thirty initially asymptomatic substage A dogs (29.4%) experienced gastrointestinal AEs. Because of the widespread use of gastrointestinal supportive care medications, statistical comparison between groups could not be performed. Seven instances of hospitalization occurred (5.0%) and the risk of hospitalization did not differ significantly between groups (P = .37).

CONCLUSIONS AND CLINICAL IMPORTANCE

Vincristine dosed at ≤0.6 mg/m2 does not increase the risk of hematologic AEs in dogs weighing ≤15 kg.

Extensive fatal Pyoderma gangrenosum in a dog after drug exposure

A 4-year-old, spayed female mixed breed dog was presented with large crater-like, well-demarcated, erosive and ulcerative necrotic lesions of the skin, elevated body temperature and lethargy, that began 14 days after vaccination and treatment with fluralaner and milbemycin/praziquantel. Cytology revealed severe pyogranulomatous inflammation with moderate numbers of extracellular microorganisms. Histopathologic examination showed severe multifocal pyogranulomatous dermatitis and panniculitis with severe dermal edema and severe neutrophilic exocytosis with band-like infiltration of the lower portion of the epidermis consistent with pyoderma gangrenosum. Despite intensive immunosuppressive and antimicrobial therapy and intensive inpatient care, the dog was euthanized 16 days after admission due to complications with clinical signs of sepsis, acute dyspnea and thoracic effusion.

Prednisolone prescribing practices for dogs in Australia

Although prednisolone is a routinely prescribed medication in dogs, there is a lack of information regarding prednisolone prescribing practices by veterinarians. This study aims to describe characteristics of dogs receiving prednisolone, disease processes treated, doses prescribed as well as to identify factors influencing the dose rate in Australia. The VetCompass Australia database was queried to identify dogs prescribed prednisolone between 1 July 2016 to 31 July 2018 (inclusive). A random sample of 2,000 dogs from this population were selected. Dog demographic data, prednisolone dose and indication for prescription were collated. Indicated dose for the condition treated was compared to prescribed dose. Multivariable linear regression was used to identify patient-level characteristics associated with prescribed prednisolone dose. A large and small breed dog cohort, treated for the same disease process, were compared for differences in dosing. Median age of dogs was 73 (range 2 to 247) months and median body weight was 17 (range 1.56 to 90) kg. Median prescribed prednisolone dose was 0.8 mg/kg/day, with most dogs receiving an anti-inflammatory dose (0.3-1 mg/kg/day, 58%). Prednisolone prescriptions were predominantly for diseases of the integument (n = 1645, 82%) followed by unknown indication and respiratory disease. A total of 152 dogs (8%) were prescribed immunosuppressive doses of prednisolone for conditions where an anti-inflammatory dose would be recommended. Increases in bodyweight were associated with lower doses on mg/kg scale but higher doses on a mg/m2 scale (p < 0.001). Overall, prednisolone was primarily used as an anti-inflammatory in this population, with some inappropriate use of immunosuppressive doses. Increasing bodyweight was associated with a small reduction in dose in mg/kg, suggesting that clinicians are adjusting prednisolone dose rates based on dog bodyweight.

Prednisolone and dexamethasone are systemically absorbed after topical application of ophthalmic suspensions in healthy dogs

OBJECTIVE

To quantify plasma concentrations of prednisolone and dexamethasone (peripheral and jugular) and cortisol following topical ophthalmic application of 1% prednisolone acetate and 0.1% dexamethasone to healthy adult dogs.

ANIMALS

12 purpose-bred Beagles.

PROCEDURES

Dogs received 1 drop of 1% prednisolone acetate (n = 6) or neomycin polymyxin B dexamethasone (ie, 0.1% dexamethasone; 6) ophthalmic suspension in both eyes every 6 hours for 14 days. Blood samples (peripheral and jugular) were collected on days 0, 1, 7, and 14 and analyzed for plasma prednisolone and dexamethasone concentrations. Plasma cortisol concentrations were measured at the beginning of the study and following topical drug administration.

RESULTS

Both drugs demonstrated systemic absorption. Prednisolone was detected on days 1, 7, and 14 (median plasma concentration, 24.80 ng/mL; range, 6.20 to 74.00 ng/mL), and dexamethasone was detected on days 1, 7, and 14 (2.30 ng/mL; 0 to 17.70 ng/mL). Neither prednisolone nor dexamethasone were detected in plasma samples on day 0 (baseline). Sampling from the jugular vein resulted in higher plasma drug concentrations than from a peripheral vein when samples from each day were combined. Plasma cortisol concentrations were significantly lower than baseline following 14 days of treatment with topical prednisolone acetate and dexamethasone.

CLINICAL RELEVANCE

Prednisolone and dexamethasone are detected in the plasma of healthy dogs following topical ophthalmic administration 4 times/d with prednisolone concentrations being close to a physiologic dose of orally administered prednisolone. Additional research is needed to evaluate the systemic absorption of these medications in dogs with ocular inflammation.