Development and application of a physiologically based pharmacokinetic model for orbifloxacin in crucian carp (Carassius auratus).

A flow-limited physiologically based pharmacokinetic (PBPK) model consisting of seven compartments was established for orbifloxacin in crucian carp to predict drug concentrations after intravenous or intramuscular injections. Physiological and anatomical parameters, including tissue weights and blood flow through different tissues, were obtained from previous literature. The tissue/plasma partition coefficients for orbifloxacin were calculated using the area method or parameter optimization. In addition, their values were 0.9326, 1.1204, 1.1644, 1.3514, and 2.0057 in the liver, skin, muscle, kidney, and the rest of the body compartment, respectively. Based on the current PBPK model, orbifloxacin concentrations were predicted and compared with those previously reported for further validation. In addition, the mean absolute percentage error (MAPE) values were also calculated, with values ranging from 10.21% in plasma to 42.37% in kidneys, indicating acceptable predictions for all tissues and plasma. A local sensitivity analysis was performed, which showed that the parameters related to elimination and distribution were most influential on orbifloxacin concentrations in muscle. This model was finally used to predict plasma and tissue concentrations after multiple intramuscular dosing. The current PBPK model provided a valuable tool for predicting the tissue residues of orbifloxacin in crucian carp following intramuscular injection.