Use of the pentagastrin dog model to explore the food effects on formulations in early drug development.

The ability to extrapolate dosage performance from in vitro to in vivo situations has an important role in early drug development. In parallel, the Beagle dog has come to represent a useful animal model for extrapolation to humans especially when drugs formulated for humans are to be tested. In this article, the pentagastrin-induced Beagle dog model was validated internally to show that in the colony the dogs were generally responsive to known doses of pentagastrin that produces effects similar to gastrin in the stomach, i.e., increasing gastric acid production and lowering gastric pH. The effect was observed with a short time course, maximum pH lowering was observed between 0.5 and 1h with return to baseline at 2-4h. The dog stomach pH is a better representative of the human fasted stomach with this pretreatment. The ultimate goal was to use these animals in a food effect studies to predict the behavior of formulations in humans. The results for 4 compounds were provided in the dog and a clear relationship between the effect of food in the dog and the effect of food in humans was observed. While the directionality (positive or negative) of the effect could be adequately predicted, the extent of the effect could not be predicted for all the tested formulations of the 4 compounds. The data will be used to generate a database of known compounds from which a correlation can be drawn to make future predictions using the pentagastrin dog model.

Improved antibacterial activities of coumarin antibiotics bearing 5',5'-dialkylnoviose: biological activity of RU79115.

A new series of coumarin inhibitors of DNA gyrase B bearing a N-propargyloxycarbamate at C-3' of various 5',5'-dialkylnoviose, including RU79115, were synthesised and their antibacterial activities have been delineated. Introduction of dialkyl substituents at 5'5'-position of noviose leads to coumarin analogues with improved in vitro and in vivo antibacterial activity.

Determination of the enantiomers of a novel 20,21-dinoreburnamenine derivative in rat plasma and brain by high-performance liquid chromatography using a chiral stationary phase.

A high-performance liquid chromatographic method with solid-phase extraction was developed for the assay of the enantiomers of a novel 20,21-dinoreburnamenine derivative (RU 49041) in rat plasma and brain using a chiral stationary phase (Nucleosil Chiral 2) and ultraviolet detection. The limit of detection was 10 ng/ml (or ng/g) in both tissues and the intra-assay precision was satisfactory (plasma, ca. 5%; brain, ca. 1%). The pharmacokinetic profiles of the two enantiomers were determined following oral administration of the racemate (10 mg/kg). The results show that their pharmacokinetics are very different: whereas both enantiomers appear in the brain, only the 3 alpha,16 beta-enantiomer is detected in plasma.