Abstract
Pharmacokinetic analysis of the plasma concentration after low dose administration of (α-bromoisovaleryl) urea (mono (2-bromo-3-methylbutyryl) urea) to rats was carried out by the nonlinear least-squares curve fitting method, and the differences of bioavailability between the polymorphic forms of the drug (form I and form II) were studied. The area under the blood concentration curve (AUC) showed no significant dependence on the administration method (intravenous solution, intraduodenal solution, intraduodenal form I and intraduodenal form II). It was apparent that (α-bromoisovaleryl) urea is absorbed rapidly and completely in the intestine after the intraduodenal administration of the solution or of the crystalline forms in gelatin solution, and there was no significant difference in the extents of biogvailability. On the other hand, the absorption rate constants, obtained by pharmacokinetic analysis based on an assumed kinetic model consisting effectively of one first-order absorption process, showed significant differences between solution and crystal suspension and between the two crystalline forms. Thus, the rate of absorption of (α-bromoisovaleryl) urea appears to depend on the polymorphic form or the administration method, even though these factors do not influence the extent of bioavailability.
