Prevalence of hepatotoxicity and myelosuppression with alternate day use of azathioprine and glucocorticoids for treatment of dermatological conditions in dogs.

BACKGROUND: The use of azathioprine (AZA) in dogs is limited by the potential for hepatotoxicity and myelosuppression. HYPOTHESIS/OBJECTIVES: To determine the prevalence of AZA-associated hepatotoxicity in dogs with dermatological conditions receiving alternate-day AZA. The hypothesis was that dogs receiving AZA every other day (EOD) would have a lower prevalence of hepatotoxicity compared to published data for dogs receiving daily AZA. A secondary aim was to determine the prevalence of AZA-associated myelosuppression over the same time period and population. ANIMALS: Forty-one client-owned dogs with dermatological conditions treated with AZA EOD and glucocorticoids with clinical and haematological follow-up available for a minimum of two months of AZA therapy. METHODS: Retrospective analysis of data from April 1994 to July 2020. Hepatotoxicity was defined as elevation of alanine aminotransferase (ALT) at least twofold above the reference range. RESULTS: Azathioprine-associated hepatotoxicity was observed in two of 41 dogs (4.9%), with onset at 18 and 40 days, respectively. One dog receiving AZA at 1.9 mg/kg EOD had a fourfold increase in ALT. The other dog (AZA dose 2.3 mg/kg EOD) had a 30-fold increase in ALT. Azathioprine was not associated with thrombocytopenia, anaemia or neutropenia in any dogs. Lymphopenia developed in one dog (2.4%) with onset at 105 days. CONCLUSIONS AND CLINICAL RELEVANCE: Alternate-day AZA administration with tapering glucocorticoids was well-tolerated in dogs with dermatological conditions.

A double-blinded, randomized, controlled, crossover evaluation of a zinc methionine supplement as an adjunctive treatment for canine atopic dermatitis.

BACKGROUND: Zinc is important for skin health and proper immune system function. HYPOTHESIS/OBJECTIVES: A zinc methionine, essential fatty acids (EFA) and biotin product (Zn supplement) was compared to an EFA and biotin product (control) in canine atopic dermatitis (CAD). ANIMALS: Twenty seven client-owned dogs with chronic CAD receiving ciclosporin or glucocorticoids. METHODS: A 24 week, randomized, double-blinded, controlled study with crossover at week 12 and 4 week period of allergy medication reduction at weeks 8 and 20. Evaluations included Canine Atopic Dermatitis Lesion Index (CADLI), pruritus Visual Analog Scale (VAS) and cytology sampling. RESULTS: In dogs receiving the zinc supplement and ciclosporin for eight weeks, 44% (n = 7) had significantly decreased CADLI from 11.9 to 6.0 (P = 0.0002) with no significant change in pruritus VAS (P = 1.0). In dogs receiving the zinc supplement and glucocorticoids for eight weeks, 55% (n = 6) had significantly decreased CADLI from 10.9 to 5.0 (P = 0.0043) and pruritus VAS from 7.4 to 3.2 (P = 0.0166). For dogs receiving either steroids or ciclosporin there was a reduction in use of such medications, for at least four weeks, in 63% of dogs receiving the zinc supplement and 37% of dogs receiving the control. This difference was not significant (P = 0.1027). Seventy eight percent of dogs were diagnosed and treated for superficial skin infections during the study. CONCLUSIONS AND CLINICAL IMPORTANCE: This study supports a potential benefit of adjunctive zinc methionine supplementation in CAD. Dogs receiving glucocorticoids may be more likely to benefit. Further studies are needed to substantiate these initial results.