Bioequivalence study of two long-acting oxytetracycline formulations in sheep.

Two commercially available long-acting oxytetracycline hydrochloride formulations (Primamycin LA (Pfizer) and Terralent 20% LA (I.E. Ulagay)) were administered by the intramuscular route to 20 clinically healthy sheep at a dose of 20 mg/kg. The study was performed in a two-period crossover design. Plasma samples were analysed by high-pressure liquid chromatography. The mean maximum concentrations (C (max)) was 8.00 +/- 2.05 microg/ml and 8.61 +/- 1.42 micro/ml, respectively. The mean area under the concentration time curve (AUC) values were 154.95 +/- 50.37(microg h)/ml and 161.70 +/- 47.02(microg h)/ml, respectively. The 90%confidence intervals for the ratio of C (max) and AUC values for the test and reference product are with in the interval 70-143% for C (max) and interval 80--125% for AUC proposed by EMEA. It was concluded that Primamycin LA and Terralent 20% LA formulations are bioequivalent in their rate and extent of drug absorbtion.