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Pharmacokinetics and Bioavailability of Azithromycin Following Intramuscular and Oral Aministrations in Broiler Chickens

Abo-El-Sooud K, Eman Fahmy, Afifi NA and Abd El-Aty AM

The pharmacokinetics azithromycin were investigated in broiler chickens after intravenous (i.v.), intramuscular (i.m.) and oral (p.o.) administrations to estimate an appropriate dosage regimen of azithromycin. Moreover, to determine the bioavailability after the extravascular routes and the serum protein binding capacitywith azithromycin‘s molecules. Three equal groups of 5 chickens each were given a single dose of 20 mg/kg body weight (bw) of azithromycin via i.v., i.m. and p.o. administrations. Serum concentrations of azithromycin were determined by a modified agar diffusion bioassay using Bacillus subtilis ATCC 6633 as the test organism. Following compartmental analysis, a three-compartment open model best described the concentration-time data of azithromycin after i.v. administration. The total body clearance (Cltot) was 0.77 L/kg/h the volume of distribution at steady-state (Vdss) was 47.75 L/kg and the value of the elimination half-life (t1/2l3) was 31.91 h.After i.m. administration, the elimination half-life (t1/2el) and mean residence time (MRT) were significantly higher (38.95 h and 47.16) than after p.o. route (31.50 h and 39.93 h), respectively. Azithromycin was bound to the extent of 24.42 % to serum protein of chickens. The absolute bioavailabilities were 95.17 and 83.52%after i.m. and p.o. administrations, respectively. Based on the fortunate pharmacokinetic characteristics, a single dose of azithromycin at 20 mg/kg (bw) via i.m. and p.o. administrations every 72 h for susceptible bacterial infections in chickens is greatly recommended.