Pharmacokinetic depletion phase of doxycycline in healthy and Mycoplasma gallisepticum -infected chicken broilers after coadministration of enrofloxacin traces

Toxicity induced by ciprofloxacin and enrofloxacin: oxidative stress and metabolism

Ciprofloxacin (CIP) (human use) and enrofloxacin (ENR) (veterinary use) are synthetic anti-infectious medications that belong to the second generation of fluoroquinolones. They have a wide antimicrobial spectrum and strong bactericidal effects at very low concentrations via enzymatic inhibition of DNA gyrase and topoisomerase IV, which are required for DNA replication. They also have high bioavailability, rapid absorption with favorable pharmacokinetics and excellent tissue penetration, including cerebral spinal fluid. These features have made them the most applied antibiotics in both human and veterinary medicine. ENR is marketed exclusively for animal medicine and has been widely used as a therapeutic veterinary antibiotic, resulting in its residue in edible tissues and aquatic environments, as well as the development of resistance and toxicity. Estimation of the risks to humans due to antimicrobial resistance produced by CIP and ENR is important and of great interest. Moreover, in rare cases due to their overdose and/or prolonged administration, the development of CIP and ENR toxicity may occur. The toxicity of these fluoroquinolones antimicrobials is mainly related to reactive oxygen species (ROS) and oxidative stress (OS) generation, besides metabolism-related toxicity. Therefore, CIP is restricted in pregnant and lactating women, pediatrics and elderly similarly ENR do in the veterinary field. This review manuscript aims to identify the toxicity induced by ROS and OS as a common sequel of CIP and ENR. Furthermore, their metabolism and the role of metabolizing enzymes were reported.

Comparison of the pharmacokinetics of tilmicosin in plasma and lung tissue in healthy chickens and chickens experimentally infected with Mycoplasma gallisepticum

The objectives of this study were to compare the plasma and lung tissue pharmacokinetics of tilmicosin in healthy and Mycoplasma gallisepticum-infected chickens. Tilmicosin was orally administered at 4, 7.5 and 10 mg/kg body weight (b.w) for the infected and 7.5 mg/kg b.w for the uninfected control group. We found no significant differences in plasma tilmicosin pharmacokinetics between diseased and healthy control chickens. In contrast, the lung tissues in M. gallisepticum-infected chickens displayed a t_1/2 (elimination half-life) 1.76 times longer than for healthy chickens. The C_max (the maximum concentration of drug in samples) of tilmicosin in M. gallisepticum-infected chickens was lower than for controls at 7.5 mg/kg b.w (p < .05), and the AUC_inf (the area under the concentration-time curve from time 0 extrapolated to infinity) in infected chickens was higher than for the healthy chickens (p < .05). The mean residence time of tilmicosin in infected chickens was also higher than the healthy chickens. These results indicated that the lungs of healthy chickens had greater absorption of tilmicosin than the infected chickens, and the rate of elimination of tilmicosin from infected lungs was slower.

Pharmacokinetics of doxycycline after oral administration of single and multiple dose in broiler chickens

As a semisynthetic tetracycline derivative, doxycycline (α-6-deoxy-5-hydroxytetracycline) is a time-dependent bacteriostatic agent. It is being widely used in the broiler husbandry in China. In this study, doxycycline was orally administered by gavage to 10 healthy broiler chickens at the dose of 20 mg/kg body weight every 24 hr for five total treatments. Plasma samples were collected from each animal at 5, 10, 20, and 30 min and 1, 2, 4, 6, 8, and 12 hr after the first dose, at 0.25, 0.5, 0.45, 1, 2, 3, 4, 6, 7, 13.5, 24, 36, 48, 60, and 72 hr after the last dose. Additional plasma samples were collected at a 24-hr interval during the dosing period (immediately prior to each oral administration). The doxycycline concentrations were determined by high-performance liquid chromatography with an ultraviolet detector and subjected to noncompartmental analysis. Then, the pharmacokinetics profiles were compared after the first and last oral doses. After the first dosing, the elimination half-life, area under the concentration-time curve from 0 hr to ∞, peak concentration, time to reach peak concentration, and volume of distribution per fraction absorbed were determined as 7.78 hr, 94.19 μg·hr/ml, 5.65 μg/ml, 3.50 hr, and 2,502.65 ml/kg, respectively, while the corresponding values of these parameters after the last dose were 19.90 hr, 121.08 μg·hr/ml, 5.71 μg/ml, 7.25 hr, and 5,285.28 ml/kg, respectively. After multiple oral doses, the absorption and elimination both became slower, while the distribution was more extensive than that following a single dose. However, after multiple oral doses, accumulation of doxycycline in plasma was not observed with an average accumulation factor of 1.11.