Combined effect of cosolvent and cyclodextrin on solubilization of nonpolar drugs

Ping Li, Luwei Zhao, Samuel H. Yalkowsky

Research output: Contribution to journalArticlepeer-review

68 Scopus citations


Solubility enhancement has broad implications in parenteral formulation design. A simple mathematical model has been developed to describe the combined effect of cosolvency and complexation on nonpolar drug solubilization. The total drug solubility is determined by the summation of three drug species present in the solution: free drug [D], drug-ligand binary complex [DL], and drug-ligand-cosolvent ternary complex [DLC]. The proposed model established the dependencies of these three species upon the intrinsic drug solubility, [D(u)], the cosolvent solubilizing power, σ, the binary and ternary intrinsic complexation constants, K(b)(int) and K(t)(int), and the cosolvent destabilizing powers for the binary and the ternary complexes, ρ(b) and ρ(t). A nonpolar solute, Fluasterone, is used to evaluate the newly generated equation. The model explains the decline in drug solubility produced by low cosolvent concentrations as well as the increase in the solubility produced by high cosolvent concentrations that are observed at all cyclodextrin concentrations.

Original languageEnglish (US)
Pages (from-to)1107-1111
Number of pages5
JournalJournal of pharmaceutical sciences
Issue number11
StatePublished - Nov 1999

ASJC Scopus subject areas

  • Pharmaceutical Science


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