Pharmacokinetics of meloxicam after oral administration of a granule formulation to healthy horses

Background: Nonsteroidal anti-inflammatory drugs are administered in horses for several systemic diseases. Selective cyclooxygenase-2 inhibitors are preferred because of lower risk of adverse effects. Several meloxicam formulations have been tested in horses, but a recently marketed granule oral formulation has not been studied. Objective: To characterize the pharmacokinetics of a novel granule meloxicam formulation in fasted and fed horses, and to compare pharmacokinetic features with oral suspension and tablets. Animals: Seven healthy adult horses. Methods: Meloxicam was administered at 0.6 mg/kg in fasted or fed horses. Blood samples were collected for pharmacokinetic analysis, and vital signs, hematology, and biochemistry variables were monitored for 72 hours. Results: No adverse effects were detected. Volume of distribution and clearance after intravenous administration of meloxicam were 0.36 L/kg and 29.12 mL/h/kg, respectively, with a 12.39 hours of terminal half-life. Protein binding was of 97%. Bioavailability was high for every oral formulation, ranging 70%-110%, without feed effect. Because of a slower absorption, meloxicam after administration of granules had a longer half-life (24 and 34 hours, fasted and fed, respectively) and mean residence time (31 and 47 hours), than suspension and tablets (ranging 10-13 and 13-15 hours, respectively). In addition, the time above therapeutic concentration was higher for the granule formulation than other formulations. Conclusions and Clinical Importance: Granule formulation has different PK parameters compared to other oral formulations, which could enable this formulation to be used for different dosage regimens in order to reach a desired clinical effect or decrease the risk of adverse effects.