Pharmacokinetics and efficacy of intravenous famotidine in adult cattle

Background: Abomasal ulceration is recognized in neonatal and adult cattle, but research regarding treatment is limited. Histamine-2 receptor antagonists (H₂RA), such as famotidine, are used clinically with little evidence-based research about efficacy in adult cattle. Hypothesis and Objectives: Intravenous famotidine administered at 0.4 mg/kg will increase the pH of abomasal outflow digesta compared to saline control in adult cattle. The objectives were to assess the effect of famotidine, administered as a single dose and as multiple doses, on abomasal outflow fluid pH in adult cattle. A third objective was to describe the pharmacokinetic parameters of IV famotidine in cattle. Animals: Four clinically healthy adult Angus-cross steers previously fitted with duodenal cannulae placed orad to the biliary and pancreatic ducts. Methods: Randomized, 2-way cross-over clinical trial. Steers received IV famotidine (0.4 mg/kg) as a single and 3-dose regimen (every 8 hours) versus saline control. Blood for analysis of serum famotidine concentration was collected intermittently for 12 hours, and abomasal outflow fluid pH was measured at intervals for a 24-hour period. After a 34-hour washout period, the opposite treatments were administered and the sampling repeated. Results: Abomasal outflow fluid pH was higher in steers treated with famotidine for up to 4 hours after a single dose but the effect decreased with subsequent doses. The median (range) elimination half-life was 3.33 (3.21-3.54) hours. Conclusions and Clinical Importance: Famotidine may be useful for treatment or prevention of abomasal ulceration in adult cattle, but the duration of effect may decrease with time.