Is the current dose of a conventional oxytetracycline formulation adequate for the management of infections in sheep?

In the veterinary industry, short-acting or conventional oxytetracycline formulations are recommended for use once a day for 4 days, at a dose of 10 mg/kg. With the large degree of antimicrobial resistance reported, the efficacy of this dose was assessed using pharmacodynamic modelling. The specific parameters evaluated were based on the time-dependent activity of the tetracycline class of antimicrobials according to the total time above minimal inhibitory concentration (T > MIC) and the ratio of the total exposure in 24 hours, represented by area under the curve (AUC24), to the minimal inhibitory concentration (AUC24:MIC). The current pharmacokinetic study examined whether the prevailing antimicrobial resistance could be overcome by doubling the recommended conventional dose. Using reported MIC data for South Africa and elsewhere, modelling indicated the presence of a large degree of resistance. In general, doubling the dose only overcame resistance of 2 bacterial species in South Africa.