Evaluation of diabetes mellitus regulation in dogs treated with ophthalmic preparations of prednisolone acetate versus diclofenac sodium

Cushing Syndrome and Other Causes of Insulin Resistance in Dogs

The most common causes of insulin resistance in diabetic dogs are Cushing syndrome, diestrus, and obesity. Cushing-associated effects include insulin resistance, excessive postprandial hyperglycemia, perceived short duration of insulin action, and/or substantial within-day and/or day-to-day glycemic variability. Successful strategies to manage excessive glycemic variability include basal insulin monotherapy and combined basal-bolus insulin treatment. Ovariohysterectomy and insulin treatment can achieve diabetic remission in about 10% of cases of diestrus diabetes. Different causes of insulin resistance have an additive effect on insulin requirements and the risk of progression to clinical diabetes in dogs.

Topical Ocular Therapeutics in Small Animals

This article reviews the administration of common topical ophthalmic medications, in relation to factors influencing absorption including composition of topical ophthalmic preparations, and potential systemic effects. Commonly prescribed, commercially available topical ophthalmic medications are discussed with respect to pharmacology, their indications for use, and adverse effects. Knowledge of topical ocular pharmacokinetics is essential for the management of veterinary ophthalmic disease.

Comparison of ophthalmic loteprednol etabonate and prednisolone acetate effects on adrenocortical response to ACTH in dogs

OBJECTIVE

This study served to compare the degree of adrenocortical suppression following a 2-week administration of loteprednol etabonate (LE) and prednisolone acetate (PA) ophthalmic drops.

PROCEDURES

In this prospective double-masked triple-crossover study, 21 clinically healthy dogs were randomized to receive loteprednol etabonate ophthalmic suspension 0.5%, prednisolone acetate ophthalmic suspension 1%, or artificial tears (AT). Each group (LE, PA, and AT) received one drop in each eye every 12 h for 2 weeks, followed by a 3-week washout period between treatment blocks. ACTH stimulation tests were performed before and after each treatment block. Serum cortisol samples were drawn before and 60 min after administration of 1 μg/kg cosyntropin IV. Repeated-measurement ANOVA followed by a Tukey's multiple comparisons test (or a Friedman test followed by a Dunn's multiple comparisons test) were used to compare pre- and post-treatment cortisol values between each group. A p-value of ≤.05 was considered significant.

RESULTS

A total of 18 dogs completed the study. Prestimulation cortisol values were lower in the PA group compared to the LE (p = .0106), but not AT (p = .0589) groups, and post-stimulation cortisol values were lower in the PA group than either LE (p = .0005) or AT (p = .0002) groups. There was no significant difference detected in pre- or post-stimulation cortisol values after the treatment periods between LE and AT.

CONCLUSIONS

Based on the reduced suppression of cortisol values, LE caused significantly less hypothalamic-pituitary-adrenal axis suppression than PA. A topical steroid with minimal adrenocortical suppression, such as LE, may be favorable in patients where systemic glucocorticoid effects should be avoided.

Relationship between HbA1c, fructosamine and clinical assessment of glycemic control in dogs

Background

Serum fructosamine is a routine test used for clinical monitoring of diabetes mellitus (DM) but the usefulness of HbA1c for this purpose has not been extensively studied.

Hypothesis

The study aimed to compare the ability of blood HbA1c and serum fructosamine tests to correctly classify DM control determined using a clinically-based assessment.

Animals

28 client-owned dogs with naturally-occurring diabetes mellitus.

Methods

Cross-sectional observational study. Ability of fructosamine and HbA1c tests to classify diabetes control in dogs was determined.

Results

Clinical assessment classified 50% of dogs as having good diabetic control and 82% as having acceptable diabetic control. Analysis using Cohen’s kappa test showed that agreements between fructosamine and HbA1c results and the clinical assessment ranged from poor to fair. Fructosamine and HbA1c results from each dog showed a moderate correlation. Overall, the HbA1c test showed the best agreement with the clinical assessment when diabetes control was considered either acceptable or unacceptable, although the strength of agreement was considered fair (kappa = 0.27).

Conclusions and clinical importance

The HbA1c concentration was found to be more consistent with clinical evaluation of diabetes control than was the serum fructosamine concentration. The HbA1c level is a useful tool for assessment of glycemic status in diabetic dogs but should be used alongside other tests for outpatient monitoring of clinically stable diabetic dogs.

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.