Populational Pharmacokinetics of Florfenicol in Nigerian Cattle Breeds Under Field Conditions

Population pharmacokinetics provides a framework for characterising drug behaviour and its sources of variability across diverse subpopulations, enabling optimised dosing recommendations that account for breed, age, sex, health status, and environmental factors. Florfenicol is a broad-spectrum synthetic antibiotic used extensively for respiratory and systemic bacterial infections in cattle across Nigeria. However, pharmacokinetic studies in Nigerian indigenous and crossbred cattle breeds under field conditions are lacking, resulting in potential under- or over-dosing when extrapolating from temperate breed data. This study characterised the population pharmacokinetics of subcutaneous florfenicol at 20 mg/kg in White Fulani, Friesian crossbred, and N'Dama cattle recruited from farms in Kaduna, Ogun, and Cross River states respectively. A total of 90 cattle, 30 per breed, were enrolled. Sparse blood sampling was performed at pre-defined time points, and plasma florfenicol was quantified by validated HPLC. Nonlinear mixed-effects modelling was used for population pharmacokinetic analysis with NONMEM software. A two-compartment model best described the data. Breed and body weight were identified as significant covariates for clearance and volume of distribution. White Fulani cattle showed significantly lower clearance compared with Friesian crossbreds, resulting in higher exposure. N'Dama cattle showed intermediate parameters. The current recommended dosing interval of 48 hours provided adequate coverage against susceptible respiratory pathogens in all breeds when MIC was 1 microgram/mL or below. These findings provide a quantitative basis for breed-specific florfenicol dosing in the diverse Nigerian cattle population. Keywords: florfenicol, population pharmacokinetics, cattle breeds, NONMEM, dosing.