Bioavailability,pharmacokinetics and residues of chloramphenicol in the chicken*

Anadón, A., Bringas, P., Martinez-Larrañaga, M.R., Diaz, M.J. Bioavailability, pharmacokinetics and residues of chloramphenicol in the chicken. J. vet. Pharmacol Therap. 17 , 52–58. The pharmacokinetic properties of chloramphenicol were determined in broiler chickens after two sinSle oral doses (30 and 50 mg/kS body weight) and after a single intravenous (i.v.) dose (30 mg/kg body weight). After oral and i.v. administration, the plasma concentration-time graph was characteristic of a two-compartment open model. After oral administration (30 and 50 mg/kg). chloramphenicol was absorbed rapidly (time to maximal concentration of 0.72 or 0.60 h) and eliminated with a mean half-life (t_½β) of 6.8 7 or 7.41 h, respectively. The bioavailability was 29% at 30 mg/kg chloramphenicol and 38% at 50 mg/kg chloramphenicol. Concentrations greater than 5 (m̈g/ml were achieved at 15 min and persisted up to 2 or 4 h post-administration, respectively. Statistically significant differences between the two routes of administration were found for the pharmacokinetic variables, half-lives of both distribution and elimination phases (t_½αt_½β) and apparent volume of distribution V_d(area)]. The mean t_½β of chloramphenicol and i.v. administration was 5.23 h. Chloramphenicol was extensively metabolized into dehydrochloramphenicol (DH-CAP), nitrophenylaminopropanedione (NPAP) and nitroso-chlorampheni-col (NO-CAP) derivatives. Residues of chloramphenicol (CAP) and the three metabolites DH-CAP, NPAP and NO-CAP in kidney, liver and muscle were measured in chickens that received an oral dose of 50 mg/kg once daily for 4 days. The results indicate that CAP and DH-CAP residues were cleared slowly and were at or below the detection limit of 0.005 m̈g/ml within 12 days after dosing. However, at the time of slaughter (12 days), the NPAP and NO-CAP residues were detected in the tissue.