Jonkman J H, Hunt C A
Pharm Weekbl Sci. 1983 Apr 29;5(2):41-8. doi: 10.1007/BF01960074.
The lipophilicity of some highly ionized drugs at physiological pH is very low. Gastro-intestinal absorption of such compounds cannot be explained by the 'pH-partition' hypothesis. Ion pair formation between a drug and an endogenous counter ion alone resulting in an electrically neutral and potentially more lipophilic species has been proposed as a mechanism to explain the observed, though deficient, absorption of ionic drugs. The concept of ion pair formation between an ionic drug and an exogenous counter ion has been the rationale for attempts to improve penetration of biological membranes and, specifically, result in increased absorption from the gastro-intestinal tract. The validity of the 'ion pair absorption hypothesis' is re-evaluated in the context of a conceptual review of relevant literature.
一些在生理pH值下高度离子化的药物的亲脂性非常低。此类化合物的胃肠道吸收无法用“pH分配”假说来解释。有人提出，药物与内源性抗衡离子单独形成离子对，从而产生电中性且可能更具亲脂性的物质，以此作为一种机制来解释离子型药物虽不充分但已观察到的吸收现象。离子型药物与外源性抗衡离子形成离子对的概念，一直是试图改善生物膜通透性、特别是提高胃肠道吸收的理论依据。本文在对相关文献进行概念性综述的背景下，重新评估了“离子对吸收假说”的有效性。
