A simple and sensitive determination method for (α-bromoisovaleryl) urea in plasma was developed by using gas-liquid chromatography with an electron capture detector, (α-Bromoisovaleryl) urea was extracted from plasma with ethyl ether and ethanol in a ratio of 5 : 1 (volume); the recovery was 97.5%. The plasma concentrations were determined by the internal standard GLC-ECD method without further clean-up by column chromatography. The detection limit was about 0.5 μg/ml in 0.1 ml plasma. In order to determine the effect of polymorphism (form I, form II, and form III) of (α-bromoisovaleryl)-urea on the bioavailiabilities, plasma levels in rats after intraduodenal administration were investigated. The areas under the blood concentration curves (AUC) and the mean dissolution times (MDT) were calculated to determine the extent of bioavailability and the rate of bioavailability, respectively. The results indicated that the polymorphic states of (α-bromoisovaleryl) urea did not show significantly different bioavailabilities.
