Bioavailability study of oral liquid and tablet forms of α-difluoromethylornithine

The purpose of this study was to assess the bioavailability of two oral preparations of difluoromethylornithine (DFMO). The current preparation of DFMO is a liquid with a concentration of 0.2 gram/ml that must be drawn up into a syringe and dispensed into a small medicine glass. This form of DFMO causes wastage of the medication. The liquid form also makes compliance and blinding difficult. Recently, a new coated tablet preparation has become available from Ilex Oncology Services (San Antonio, TX). The coated tablets are 0.25 gram and are scored. The tablet form should increase compliance by making it much easier for the subject to take the medication. This report compares the bioavailability of both preparations with the goal of demonstrating equivalence of the preparations. Ten normal subjects entered the cross-over study in which the order in which they would receive the liquid or tablet preparation of DFMO was randomized. The study was designed with the objective of establishing the bioequivalence of a tablet preparation of DFMO at daily dose 0.5 gram/m² and a liquid preparation of DFMO at the same daily dose. The mean area under the time-by-concentration curves (μM x hours) for the liquid and tablet preparations was 368.2 and 370.4, respectively. The peak concentrations for the liquid and tablet preparations were 47.3 and 48.2 μM, respectively. No statistically significant differences were seen in these parameters, in time to peak concentration, or in serum half-life. The criterion for bioequivalence of the two preparations was satisfied.