The aim of this study was to measure the concentrations of enrofloxacin (ERFX) and other
fluoroquinolones; orbifloxacin (OBFX), marbofloxacin (MBFX), and ofloxacin (OFLX) in the
plasma and bile of rabbits after a single intravenous (IV) injection. Twenty male rabbits
were divided into four groups and given each drug by IV injection into the ear vein at a
dose of 5.0 mg/kg BW. The concentration of ERFX, ciprofloxacin (CPFX), OBFX, MBFX and OFLX
in plasma and bile were determined by HPLC. CPFX, metabolite of ERFX, was also measured by
HPLC in plasma and bile of rabbits receiving ERFX. Several pharmacokinetic parameters in
plasma were calculated and biliary clearance (CL
bile
) was calculated from
extent of biliary excretion and accumulation of AUC of each drug. After IV injection,
elimination half-life (t
1/2β
) was 4.13, 3.68, 6.60, 5.14 hr; volume of
distribution at a steady state (V
dss
) was 1.24, 0.503, 0.771, 1.02 L/kg; and
total body clearance (CL
tot
) was 1.05, 0.418, 0.271, 0.453 L/kg/hr,
respectively. The values for CL
bile
for ERFX, OBFX, MBFX, and OFLX were 0.0048,
0.0050, 0.0057, and 0.0094 L/kg/hr, respectively. These values represent 0.48%, 1.2%,
2.1%, and 2.3% of the total body clearance (CL
tot
) of each drug, respectively.
The biliary clearance of CPFX was also measured and found to be 0.0199 L/kg/hr with ERFX
administration. The results showed that ERFX, OBFX, MBFX, and OFLX were not excreted into
the bile to a significant extent, making them safe drugs to use in rabbits.