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.