Comparative Pharmacokinetics of Enrofloxacin After SubcutaneousAdministration of a Novel in situ Gel Forming Preparation and aConventional Product to Rabbits

Frequent drug dosing and animal handling are usually required in conventional antimicrobial therapy but sustained release formulations can improve compliance.

This study aimed to evaluate the pharmacokinetic (PK) parameters of a novel sustained release enroflox-acin (ENR) hydrogel in comparison to a conventional ENR formulation in rabbit animal model.

A total of 20 rabbits were randomly divided into three groups and received a single dose of ENR or blank by subcutaneous (SC) injection as following: Group 1 (n=8) received ENR (10 mg/kg) using a conventional product (Enrovet®); Group 2 (n=8) received ENR (33.3 mg/kg) using a hydrogel formulation; and Group 3 or control group (n=4) received equal volumes of a blank hydrogel formulation. Blood samples were collected at different time points post-dosing. ENR concen-trations in plasma were estimated by high-performance liquid chromatographic (HPLC) method and PK parameters were calculated using a non-compartmental analysis.

The ENR hydrogel released the drug in a sustained manner with mean residence time (MRT) of 78.4 ± 15.3 h, which was significantly more than that of the conventional formulation (7.39 ± 2.37 h, p <0.05). However, maximal plasma concentration (Cmax) for ENR hydrogel (1.41 ± 0.76 μg/mL) was significantly less than that of the conventional product (2.86 ± 0.79 μg/mL). The relative bioavailability (Frel) was not significantly different between the two formula-tions.

The hydrogel formulation significantly increased the MRT of ENR. Hence, it could be a promising delivery system to prolong the pharmacological activity of ENR in animals and enhance compliance.