Abstract
The wide use of antibiotics in animal production has contributed an important benefit for the health and the well-being of animals. However, the use of antibiotics has been recently criticized and there have been legal pressures to avoid it, due to the lack of a clear relation between its beneficial effects and its risk.The oxytetracycline, because of its broad bacterial spectrum and its wide prevention and therapeutic use, is within the group of antibiotics that has been mostly criticized. The possible perjudicial effect on the health of the potential consumers and the possible lack of effectiveness, have encouraged us to study in detail the pharmacokinetics characteristics that this group of drugs present after its administration by intramuscular bovine route. We have studied as well the effectiveness of the treatment and the possible presence of residues in animal tissues intended for human consumption.
In order to perform the kinetic study, we administered two commercial long acting formulations by intramuscular route at single doses of 30 mg/kg into to neck to 14 cows, whose weight was bet8ween 125 and 130 kg, We took samples from serum at different times from sampling up to 10 days post administration. Those samples were analyzed by high performed liquid chromatography (HPLC) and according to an analytic method previously validated. The following pharmacokinetics parameters were calculated: maximum concentration (Cmax), Area under curve (AUC), Mean residence time (MRT), maximum time (Tmax) and half life (T1/2). The bioequivalence between the two formulations used was evaluated and finally the therapeutic effectiveness of this drug in front of different microorganisms causing the respiratory diseases.
In order to study the residues of oxytetracycline, we administered a long acting formulation by intramuscular route (30mg/kg) to 12 cows. The animals were then slaughtered at different times (28, 35 and 42 days following administration). Samples of the different target tissues (muscle, liver and kidney) were collected and they were analyzed using high performance liquid chromatograph in accordance with analytical method previously validated. The withdrawal period was calculated for this speciality.
The results of the pharmacokinetic study showed that both formulations belonged to a kinetic profile of a long acting formulation and the values for the t1/2? and the MRT obtained after the administration were highly significant. It was shown that both formulations were bioequivalent.
The effectiveness study showed that both formulations were effective against the Mycoplasme hyopneumoniae and Moraxella Boris.
The withdrawal period was 45.5 days for the case of kidney and 54.6 days for the case of liver. It was not possible to calculate those values for the case of the muscle and in the injection site due to the presence of concentrations beyond the maximum limit of residues.
| Date of Award | 20 Nov 2006 |
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| Original language | Spanish |
| Supervisor | Margarita Arboix Arzo (Director) & Belén Pérez Fernández (Director) |