Enhanced Solubility of Ibuprofen by Complexation with β-Cyclodextrin and Citric Acid

The ability of β-CD to form inclusion complexes with ibuprofen (IBU) and at the same time to make a two-phase system with citric acid was explored in the present study for achieving improved solubility and dissolution rate of IBU. Mechanical milling as well as mechanical milling combined with thermal annealing of the powder mixtures were applied as synthetic methods. Solubility and dissolution kinetics of the complexes were studied in compliance with European Pharmacopoeia (ICH Q4B). β-CD and citric acid (CA) molecules were shown to interact by both ball milling (BM), thermal annealing, as well as BM with subsequent annealing. Complexes were also formed by milling the three compounds (β-CD, CA and IBU) simultaneously, as well as by a consecutive first including IBU into β-CD and then binding the formed β-CD/IBU inclusion complex with CA. As a result, ternary β-CD/IBU/CA complex formed by initial incorporation of ibuprofen into β-CD, followed by successive formation of a two-phase mixture with CA, exhibited notably improved dissolution kinetics compared to the pure ibuprofen and slightly better compared to the binary β-CD/IBU system. Although the addition of CA to β-CD/IBU does not significantly increase the solubility rate of IBU, it must be considered that the amount of β-CD is significantly less in the ternary complex compared to the binary β-CD/IBU.