Pharmacokinetic behavior of doxycycline after intramuscular injection in sheep.

Objectives--To determine the pharmacokinetics of a commercial formulation of doxycycline hyclate after IM administration of a single dose to sheep. Animals--11 healthy domestic sheep. Procedures--For each sheep, doxycycline was administered as a single dose of 20 mg/kg, IM. Blood samples were obtained prior to and for 84 hours after doxycycline administration. Plasma concentrations of doxycycline were determined via high-performance liquid chromatography with UV detection. Pharmacokinetic data were analyzed with noncompartmental methods. Results--Mean ± SD values for pharmacokinetic parameters included maximum plasma concentration (2.792 ± 0.791 µg/mL), time to reach maximum plasma concentration (0.856 ± 0.472 hours), mean residence time (91.1 ± 40.78 hours), elimination half-life (77.88 ± 28.45 hours), and area under the curve (65.67 ± 9.877 µg•h/mL). Conclusions and Clinical Relevance--Results indicated that doxycycline had prolonged absorption and elimination in sheep after IM administration. A daily dose of 20 mg/kg would be sufficient to reach effective plasma concentrations against Chlamydia spp (minimum inhibitory concentration, 0.008 to 0.031 µg/mL) and Staphylococcus aureus (minimum inhibitory concentration, 0.12 µg/mL). Doxycycline administered IM could be an option for therapeutic use in sheep, although further studies are needed. [ABSTRACT FROM AUTHOR]