Normal Dogs Treated with Famotidine for 14 days Have Only Transient Increases in Serum Gastrin Concentrations

Background In people, serum gastrin concentrations increase in response to administration of H 2 receptor antagonists, but the effect of famotidine administration on serum gastrin concentrations has not been evaluated in dogs. Objectives To determine if serum gastrin concentrations increase in response to 14 days of famotidine treatment and the time needed to return to baseline after discontinuation of famotidine; define stability of gastrin in samples held at room temperature. Animals Eleven healthy dogs were included in part A (famotidine treatment) and 7 healthy dogs in Part B (serum gastrin stability). In part A , famotidine (0.5 mg/kg PO q12h) was administered for 14 days. Fasting blood samples were collected on days 0, 3, 7, 11, 14, 16, 18, 20, and 22. In part B , blood was collected after a 12‐hour fast. Gastrin concentrations in serum samples held at room temperature for ≤30 minutes after sampling were compared to concentrations in samples held at room temperature for 150 minutes after sampling. Results Serum gastrin concentrations increased by day 3 of famotidine administration and returned to baseline concentrations in all dogs by day 14 despite continued famotidine administration. Serum gastrin concentrations were lower (20% mean decrease; P  = .0005) in samples held at room temperature for 150 minutes. Conclusions and Clinical Importance After 14 days of famotidine administration, clinically healthy dogs have normal serum gastrin concentrations. In a dog with clinical features consistent with gastrinoma, chronic famotidine administration is unlikely to contribute to increases in serum gastrin concentrations.