Fig. 6. A summary of how complexed drugs may be released from a delivery vehicle. (A) The intact complex may release directly from the particle into the bulk. This type of release is a function of the complex's solubility in the bulk, so hydrophobic sinks such as bile salt micelles or albumins in the bulk phase will provide more of a driving force than simply a buffer. (B) Salts lead to counterion competition and decomplexation, which is followed by release as the water-soluble drug is released into the bulk. (C) When counterions such as fatty acids are used, lowering the pH below their pKa will lead to protonation. The protonated counterions will no longer complex the drug, leading to release as in (B).
