Injection site influences pharmacokinetics and tissue distribution of danofloxacin following a single intramuscular dose in white sturgeon (Sinosturio transmontanus)

Objective: To characterize the pharmacokinetics of danofloxacin following IM administration at 2 injection sites in white sturgeon (Sinosturio transmontanus). Methods: Healthy subadult white sturgeon housed at the University of California-Davis Center for Aquatic Biology and Aquaculture were used for an in vivo experimental pharmacokinetics study. Over 3 weeks, sturgeon received a single IM injection of danofloxacin (10 mg/kg) in either the dorsal epaxial muscle or the pectoral base muscle. Plasma samples were collected from the caudal vein at 16 time points after administration, and gill, muscle, posterior kidney, and brain tissues were collected at 5 time points. Danofloxacin concentrations were quantified using LC-MS-MS. Results: Maximum plasma concentrations occurred approximately 20 minutes after administration for both injection sites. Danofloxacin was detected in all tissues examined (n = 4/time point/group). Plasma concentrations were significantly increased following pectoral administration during the first 12 hours after injection. Tissue concentrations were also significantly increased following pectoral administration in all tissues during the first hour and in the posterior kidney after 12 hours. No adverse effects from injections were observed. Conclusions: A single IM dose of danofloxacin in white sturgeon produced rapid plasma and tissue absorption for both injection sites. Pectoral administration significantly increased early drug concentrations compared to epaxial administration. Clinical Relevance: These findings provide clinically relevant information to support evidence-based antimicrobial use in sturgeon and other fish species. Clinicians may consider the benefits of pectoral administration when developing therapeutic plans, particularly in acute cases requiring rapid drug distribution.