Correlation between oral fluid and plasma oxytetracycline concentrations after intramuscular administration in pigs.

Abstract

The penetration of oxytetracycline (OTC) into the oral fluid and plasma of pigs and correlation between oral fluid and plasma were evaluated after a single intramuscular (i.m.) dose of 20mg/kg body weight of long-acting formulation. The OTC was detectable both in oral fluid and plasma from 1hr up to 21day after drug administration. The maximum concentrations (Cmax ) of drug with values of 4021±836ng/ml in oral fluid and 4447±735ng/ml in plasma were reached (Tmax ) at 2 and 1hr after drug administration respectively. The area under concentration-time curve (AUC), mean residence time (MRT) and the elimination half-life (t1/2β ) were, respectively, 75613 ng×hr/ml, 62.8hr and 117hr in oral fluid and 115314 ng×hr/ml, 31.4hr and 59.2hr in plasma. The OTC concentrations were remained higher in plasma for 48hr. After this time, OTC reached greater level in oral fluid. The strong correlation (r=.92) between oral fluid and plasma OTC concentrations was observed. Concentrations of OTC were within the therapeutic levels for most sensitive micro-organism in pigs (above MIC values) for 48hr after drug administration, both in the plasma and in oral fluid.