Candesartan cilexetil (CC) occurs in a slightly negatively charged form, and the trend for enhancing CF permeability was confirmed, similarly to ASC and NX. Furthermore, there was a significant decrease in the partition coefficient. This may have been because CC is a very lipophilic and large molecule, which may have displaced CF from the membrane by its presence in the membrane during co-permeation. Consequently, the partition coefficient of CF was significantly reduced.