Trilostane is considered an efficacious and safe medication for canine pituitary-dependent hyperadrenocorticism (PDH). Its recommended frequency of administration is once daily. In this prospective study, the efficacy, toxicity, and long-term outcome of trilostane administered twice daily per os were evaluated in 44 dogs with PDH. Mean initial dose was 3.1 mg/kg q 12 hours, and mean final dose was 3.2 mg/kg q 12 hours. The final total daily dose was lower than previously reported for once-daily administration. The mean survival time for affected dogs was 930 days.

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BackgroundTreatment of adrenal‐dependent hyperadrenocorticism (ADH) involves either surgical resection of the adrenal tumor or medical therapy. For many years, mitotane has been considered the medical treatment of choice for dogs with ADH.ObjectivesThe aim of this study was to determine survival and prognostic factors for dogs with ADH treated with mitotane and trilostane.AnimalsTwenty‐six dogs with ADH were included in the study.MethodsFourteen dogs were treated with mitotane and 12 dogs were treated with trilostane. Medical records were reviewed. Epidemiologic factors, signalment, clinicopathologic abnormalities, endocrine test results, and treatment protocols were evaluated to identify potential predictive factors of overall survival time.ResultsSurvival times of dogs treated with mitotane (median, 15.6 months) or trilostane (median, 14.0 months) were not significantly different. Using univariate analysis, age and postadrenocorticotropic hormone cortisol concentrations were inversely correlated with survival time. The multivariate model also identified weakness at presentation as a negative prognostic indicator.Conclusion and Clinical ImportanceThe type of medical treatment (mitotane versus trilostane) does not influence survival time in dogs with ADH; therefore, trilostane, a drug with less frequent and milder adverse effects, might be used as the primary medical treatment when adrenalectomy cannot be performed.

Background: Trilostane is the drug of choice to treat pituitary-dependent hyperadrenocorticism (PDH) in dogs, but there is still controversy about which protocol best controls the clinical signs and results of adrenal functioning test.Objectives: To compare the efficacy of twice daily (BID) versus once daily (SID) trilostane administration and to compare the safety of both protocols in the treatment of dogs with PDH.Animals: Thirty-two client-owned dogs diagnosed with PDH between 2008 and 2010 and treated with trilostane either BID or SID.Methods: In this prospective randomized study, 2 trilostane protocols were evaluated on the basis of the owner′s perception of clinical signs, on the results of laboratory tests, and on the results of the ACTH stimulation test in dogs with PDH. Dogs were followed up for a period of 1 year.Results: During the study, more dogs in the BID group had complete clinical recovery than in the SID group. However, there was no significant difference in the mean post-ACTH cortisol concentration between groups. Basal cortisol concentration at 6 months was higher in animals treated SID compared with animals treated BID. Mean total daily doses of trilostane used to control PDH, as well as adverse effects observed in the course of the study, in both groups were not statistically different.Conclusion and Clinical Importance: Adverse effects were mild using either protocol of treatment. Using trilostane BID might increase the number of dogs with a good clinical response compared with using trilostane SID.

Cyclooxygenase-2 (Cox-2) enzyme participates in different steps of the carcinogenetic process and in canine mammary tumours (CMTs), a high expression of Cox-2 is associated with malignancy and tumour angiogenesis. The objectives of the study were to evaluate the disease-free survival (DFS) and overall survival (OS) of a Cox-2 inhibitor as adjuvant therapy in dogs with highly malignant (HM)-CMTs and compare it with that of dogs treated with chemotherapy and with control dogs. Twenty-eight dogs were prospectively included. After surgery, dogs were alternatively allocated into two treatment groups (chemotherapy with mitoxantrone n=8; Cox-2 inhibitor, firocoxib n=7). Control group (n=13) included dogs whose owners rejected adjuvant therapy. All dogs were followed up for two years or until death. The DFS was significantly higher in dogs that received adjuvant treatment (mitoxantrone or firocoxib) (P=0.030) than in control dogs. Dogs on firocoxib treatment had significantly higher DFS (P=0.015) and OS (P=0.048) than control dogs. The DFS and OS of dogs on mitoxantrone treatment were not statistically different from controls. In conclusion, this study supports the use of firocoxib for the treatment of HM-CMTs. Further studies are needed to compare the efficacy of chemotherapy drugs versus Cox-2 inhibitors as adjuvant treatment in these cases.