الفهرس 
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Abstract
In the present work, the pharmacokinetic parameters of cefadroxil after single intravenous injection or oral and repeated oral administrations in normal and experimentally infected chickens were studied in thirty five clinically normal Hubbard chicken ( 20 normal and 15 experimentally infected chicken). Chickens were divided into three groups . The bioavailability of cefadroxil was calculated in normal chickens. The disposition kinetics as well as tissue residues after repeated administration of cefadroxil once daily for five consecutive days in normal and experimentally infected chickens were studied.Following a single intravenous injection of cefadroxil 20 mg/kg b.wt. in normal chickens, cefadroxil could be detected therapeutically till 24 hours post intravenous injection with value equal to 0.19 ± 0.01 µg/ml. The serum concentration time curve of cefadroxil following intravenous injection showed that the drug obayed to a first order two-compartments open model. cefadroxil after intravenous dose revealed a rapid distribution phase ( α = 3.85 h-1 ) with a distribution half –life (t0.5(α) ) of 0.18 h. The volume of distribution which calculated by steady state method [v(dss) ] were 629 ml/kg. cefadroxil was transferred from central to peripheral compartment [k12] at slower rate (2.04 h-1) than its passage from peripheral to central compartment [k21] (0.92 h-1) . cefadroxil was decreased after intravenous injection with a half-life [ t0.5(β) ] value of 4.85 hours and cleared by all clearance processes in the body at rate of 0.185 L/hr/kg.Following a single oral administration of cefadroxil 20 mg /kg. b.wt. in normal chickens,the drug reached its maximum plasma concentrations after 1 hours of administration with value equal to 18.91 µg/ml. cefadroxil could be detected in a therapeutic concentration 24 hours post oral administration with value equal to 0.31 µg/ml.The pharmacokinetic parameter revealed at maximum time ( Tmax) at about 1.47 hours,the absorption half-life [t0.5(ab)] was 0.71 hours, the elimination half-life [ t0.5(β) ] was 5.58 hours .The mean systemic bioavailability of cefadroxil following a single oral administration in normal chickens was 77.18 %, this value revealed a better absorption of cefadroxil from gastro intestinal tract .The serum concentrations of cefadroxil in normal and experimentally Echerichia coli infected chickens following repeated oral administration of 20 mg/kg b.wt. once daily for consecutive days , peaked hours after each oral dose with lower significant values recorded in experimentally Echerichia coli infected chickens than in normal chickens . This observation might be attributed to the higher penetrating power of the drug to diseased These concentrations were reached at maximum time (tmax) which were significantly higher in experimentally Echerichia coli infected chickens than in normal chickens. The elimination half-lives [ t0.5(β) ] of cefadroxil were significantly lower in experimentally Echerichia coli infected chickens than in normal chickens .Tissue residues of cefadroxil in slaughtered normal and Echerichia coli infected chickens following the dosage regimen of cefadroxil 20 mg/ kg b.wt. once daily for five consecutive days was significantly lower in experimentally Echerichia coli infected chickens than in normal chickens. Cefadroxil could not be detected in all tested tissue except in liver, kidney, at 72 and 48 hours, respectively in normal chickens and in liver and kidney at 72 and 48 hours, respectively in experimentally Echerichia coli infected chickens post last administration .Cefadroxil was completely cleared from all tissues at 72 hours after the stoppage of drug dosage in normal chickens .Cefadroxil was completely cleared from all tissues at 72 hours after the stoppage of drug dosage in experimentally Echerichia coli infected chickens Treated chickens must not be slaughtered before 4 days from last dose of repeated administration of cefadroxil to withdraw the drug residues from all tissues of treated chickens.