Pharmacokinetics of Cephalexin Following Multiple Dose Oral Administration in Broilers

The pharmacokinetics and tissue residue study of Cephalexin was undertaken by multiple (5) oral dose (40mg.kg-1 b.w.) administration in broiler poultry for calculating the dosage regimen and withdrawal period. The analysis of Cephalexin in plasma and tissue residue concentration was done using High Performance Liquid Chromatography (HPLC). The peak plasma concentration of Cephalexin following first day and fifth day of multiple dose were, 3.714 and 3.347 ?g.ml^-1, respectively at 1 h. Following first dose of multiple (5) dose study the C_max, T_max, t1/2?, t1/2a, AUC, CL/F and V/F were estimated as 3.255 ?g.mL^-1, 1.464 h, 1.139 h, 1.147 h, 13.067 ?g.mL^-1.h, 3.073 L.kg^-1.h^-1 and 5.06 L.kg^-1, respectively. Whereas after administration of the last dose of multiple (5) dose study the Cmax, Tmax, t1/2?, t1/2a, AUC, CL/F and V/F were estimated as 2.923 ?g.mL^-1, 1.372 h, 2.164 h, 0.886 h, 13.159 ?g.mL^-1.h, 3.07 L.kg^-1.h^-1 and 6.11 L.kg^-1, respectively. Tissue residues following multiple (five) oral dose (40mg.kg^-1 b.w.) administration were detected highest in the kidney and lowest in the spleen at 48hr while at 72hr, residues were only detected in liver and kidney and no residues were found in heart, muscles, spleen, lungs, and fat. Therefore, based upon the present study, it can be concluded that dose after multiple (5) dose study in broilers is 11.5 mg.kg^-1, respectively. A pre-slaughter withdrawal period of 4 days is recommended following multiple (5) oral dose (40mg.kg^-1 b.w.) administration in broiler poultry.