Biological availability and in vitro dissolution of oxytetracycline dihydrate tablets.

1 The concentration of oxytetracycline in plasma was studied by microbiological assay after oral administration of four different preparations of oxytetracycline dihydrate tablets. 2 There were statistically significant differences in biological availability between the four preparations, as assessed by the peak plasma level, the area under the plasma concentration-time curve, or the cumulative fraction of the dose excreted in urine at 405 minutes. In contrast, differences between the subjects were not statistically significant. 3 The differences in biological availability were not predictably related to the in vitro dissolution of the tablets.