Three canine media
Canine FaSSIF/FaSSGF is a powder that can be used to prepare three different canine biorelevant media for in vitro laboratory testing:
1.    Canine fasted state intestinal fluid (FaSSIFc)
2.    Canine fasted state gastric fluid pH 1.5 (FaSSGFc pH1.5)
3.    Canine fasted state gastric fluid pH 6.5 (FaSSGFc pH6.5)
These media are described in the Solubility Chapter <1236> of the US Pharmacopeia.
Two canine gastric fasted state media
There are two fasted state canine gastric in vitro media which reflect in vivo pHs of the canine stomach fluids. Often in preclinical in vivo studies, pentagastrin is administered which lowers the in vivo pH of the dog stomach fluid. This is important when testing basic drugs because low stomach pH can significantly influence the dissolution behaviour by increasing drug solubility.
Without administration of pentagastrin, the pH of canine in vivo fasted state gastric fluid can be significantly higher which is reflected by higher pH 6.5 of in vitro FaSSIFc.
Why are they used?
These in vitro media can be used either in preclinical development of new chemical entities or in veterinary drug product development to obtain dissolution profiles of formulations containing water insoluble drugs.
USP dissolution apparatus
Like all biorelevant test media, dissolution can be carried out using any USP dissolution apparatus. However, dissolution apparatus 2 is most commonly used.