Pharmacokinetics of Enrofloxacin in Rohu (Labeo rohita): A Comparison of Bath, Intramuscular, and Oral Administration

Abstract

Enrofloxacin, fluoroquinolone antibacterial drug is widely used in aquaculture for the control of infectious diseases. Understanding the pharmacokinetics of enrofloxacin in Labeo rohita is critical for developing optimized therapeutic strategies so as to maximize efficacy and to minimize the emergence of resistant pathogens. Hence, the present study was aimed at studying the pharmacokinetics of enroflocacin in rohu fish (Labeo rohita). The pharmacokinetics of enrofloxacin was studied after single intramuscular or oral administration at 10 mg/kg body weight and following bath exposure at the concentration of 5 mg/L for 5 h. Blood samples were collected at predetermined time intervals. The plasma concentrations of enrofloxacin were determined by high performance liquid chromatography. The pharmacokinetic parameters were analyzed using a non-compartmental method. Cmax and Tmax varied depending on the route of administration, with intramuscular administration resulting in highest plasma concentration in short Tmax indicating rapid and better absorption.  Similarly, AUC0-∞ was found to be highest (166.51 μg.h.mL-1) following intramuscular administration indicating higher total systemic drug exposure compared to oral and bath exposure. Elimination half-life (t1/2) was found to be 43.31, 34.65, and 21.66 h following intramuscular, oral, and bath exposure, respectively. Intramuscular administration provided the highest plasma concentrations and the longest elimination half-life, suggesting its suitability for sustained treatment efficacy. The volume of distribution (Vd/F) was found to be maximum after oral administration (6.52 L/kg) as compared to the intramuscular route (3.75 L/kg) and bath exposure (2.07 L/kg). The results of our study indicate that enrofloxacin was well absorbed, widely distributed, and slowly eliminated in rohu following all three routes of administration. Our results suggest that enrofloxacin administered intramuscularly (10 mg/kg), orally (10 mg/kg), or by bath immersion (5 mg/L for 5 h) achieves sufficient plasma concentrations to treat pathogens with MIC ≤ 0.3 μg/mL.