In Vivo Animal Spices and Experimental Technique to Evaluate Sustained Release Granules

Establishment of a suitable animal model to evaluate sustained release (SR) formulations is very important because it reduces the development time of SR formulations. Beagle dogs are often used to evaluate prototype formulations since they can be directly administered powder, such as drug substance. However, the physiological condition of dogs is very different to that of humans. Therefore, the benefits of utilizing beagle dogs for the evaluation of modified release formulations such as sustained release formulations and enteric-coated formulations are doubtful. To clarify the best animal and/or experimental technique for the evaluation of modified release formulations, we investigated dipyridamole pharmacokinetics from prototype sustained release granules by utilizing beagle dogs, propantheline bromide-treated (PBT) beagle dogs, and miniature pigs. In normal dogs, the intestinal absorption and sustained release effect of dipyridamole decreased in the 20 mg sustained release granule. However, in PBT dogs, a sustained release effect was observed in the 45 mg sustained release granule, and its bioavailability was also maintained. Accordingly, PBT dogs could be the best to evaluate sustained release formulations such as tablets and granules, and the use of miniature pigs might be better to evaluate granules with equal to or less than 1 mm diameter.