2017 Volume 22 Issue 1 Pages 107-114
Drugs are exposed to drastic pH changes following oral administration, for instance, from pH 1 in the stomach to pH 6 in the small intestine for healthy subjects. In the case of poorly soluble basic drugs, which exhibit pH-dependent solubility in the range of pH 1–6, supersaturation may occur, inducing higher absorption. Therefore, it is preferable to simulate the effect of various pH changes in the gastrointestinal tract for oral formulation studies. The results of in vivo studies with humans or animals may not accurately show how pH changes can effect drug dissolution and absorption in reality. In the present study, we constructed a new in vitro experimental system that can reflect the changes induced by dramatic shifts in pH. Albendazole (ABZ) was selected as a lipophilic weak basic model drug. Supersaturation of ABZ was induced by pH changes in a dynamic condition, which led to a higher permeation than that observed under the constant pH condition. This changeable pH dissolution/permeation system can simulate the effects of drastic pH shifts without the need for humans or experimental animals.
