The Effect of Delivery Method on the Pharmacokinetic Properties of Meloxicam in Pre-Weaned Dairy Calves with Diarrhea

The non-steroidal anti-inflammatory drug meloxicam is commonly used as adjunct therapy for neonatal calf diarrhea to control pain and inflammation. The objective of this study was to compare the pharmacokinetics of meloxicam in diarrheic pre-ruminant dairy calves dosed either orally or subcutaneously. Twelve pre-ruminant male dairy calves with mild to moderate diarrhea were randomly assigned to receive one of four treatments (three per group): subcutaneous meloxicam (SM, 0.5 mg/kg body weight); an oral bolus meloxicam suspension (OM, 1 mg/kg body weight); an oral meloxicam suspension added to a feeding of oral electrolytes (EM, 1 mg/kg body weight); and an oral meloxicam suspension added to a feeding of milk replacer (MM, 1 mg/kg body weight). The predicted pharmacokinetic parameters for OM, MM, EM, and SM groups were: half-life (56.8 ± 21.7 vs. 136.0 ± 26.6 vs. 85.2 ± 21.7 vs. 36.3 ± 21.7 h), Cmax (4.3 ± 0.4 vs. 3.7 ± 0.4 vs. 3.9 ± 0.4 vs. 2.1 ± 0.4 μg/mL), Tmax (13.3 ± 4.0 vs. 10.7 ± 4.0 vs. 13.3 ± 4.0 vs. 2.7 ± 4.0 h), and AUC0-∞ (383.4 ± 126.8 vs. 877.8 ± 155.3 vs. 457.1 ± 126.8 vs. 126.4 ± 126.8 h * μg/mL). Oral meloxicam, especially MM, had extended elimination phases relative to SM. All meloxicam therapies provided effective therapeutic levels but all oral therapies (1 mg/kg) provided longer durations of activity than injectable meloxicam (0.5 mg/kg).