Pharmacokinetics and tissue residues of netilmicin and vancomycin in chickens

Following a single intravenous injection of 10 mg netilmicin or 30 mg vancomycin/kg b.w. to normal chickens, the tested drugs obeyed a two or three compartments open model, with half-lives of distribution of 0.30 and 0.20 hours, respectively. The elimination half-lives following intravenous injection were 0.41 and 4.85 hours, respectively. Following a single intramuscular injection of 10 mg netilmicin or 30 mg vancomycin/kg b.w. to normal chickens, the serum drug concentrations peaked 2 hours post-injection with half-lives of absorption equal to 0.63 and 0.56 hours, respectively. The mean systemic bioavailability of netilmicin and vancomycin following a single intramuscular administration in normal chickens was 27.29 and 43.61\%, respectively. These values indicated a limited and moderate absorption for netilmicin and vancomycin from intramuscular site, respectively. During repeated intramuscular administrations of both antibiotics for five consecutive days in normal chickens, the serum drug concentrations peaked two hours post each dose. The drugs concentrations during multiple dosage regimens were significantly increased in 2nd, 3rd, 4th and 5th days in comparison to the Ist day. Netilmicin and vancomycin persisted in liver and kidney for 96 and 120 hours, respectively, after the last intramuscular administration. The withdrawal time of netilmicin and vancomycin could be considered as five and six days, respectively. The in-vitro protein binding percents of netilmicin and vancomycin were 7.45 and 5.81\%, respectively.