Ternary inclusion complex formation and stabilization of limaprost, a prostaglandin E1 derivative, in the presence of α- and β-cyclodextrins in the solid state

Limaprost/α-cyclodextrin (CD)/β-CD ternary inclusion complex was prepared by freeze-drying a solution containing all three components. Under humid conditions, limaprost was more stable in the ternary α-/β-CD inclusion complex than in the binary α- or β-CD complex. Specifically, during storage at 30°C/75% relative humidity (R.H.) for 4 weeks, about 19% of limaprost degraded into 17S,20-dimethyl-trans-Δ(2)-prostaglandin A1 (referred as 11-deoxy-Δ(10)) in the β-CD complex, 8.1% degraded in the α-CD complex, and only 2.2% degraded in the α-/β-CD complex. The mechanism of limaprost stabilization in the presence of both CDs was investigated by Raman and solid-state NMR spectroscopy and powder X-ray diffractometry. The fast degradation of limaprost to 11-deoxy-Δ(10) in the β-CD complex was due to the rapid crystallization of β-CD from the complex, liberating the free amorphous drug, which is susceptible to degradation. The dissociation and crystallization of β-CD from the inclusion complex were suppressed by freeze-drying limaprost in the presence of both α- and β-CDs. In addition, the interaction between limaprost and the two CDs was reinforced by inclusion of different moieties of limaprost: α-CD predominantly included the alkyl ω-chain, whereas β-CD included the five-membered ring. Thus, a stable ternary inclusion complex was formed that included limaprost, maintaining the amorphous state of the complex and dramatically stabilizing the drug under humid conditions.

Febuxostat ternary inclusion complex using SBE7-βCD in presence of a water-soluble polymer: physicochemical characterization, in vitro dissolution, and in vivo evaluation

Febuxostat (FBX), a potent xanthine oxidase inhibitor, is widely used as a blood uric acid-reducing agent and has recently shown a promising repurposing outcome as an anti-cancer. FBX is known for its poor water solubility, which is the main cause of its weak oral bioavailability. In a previous study, we developed a binary system complex between FBX and sulfobutylether-β-cyclodextrin (SBE7-βCD) with improved dissolution behavior. The aim of the current study was to investigate the effect of incorporating a water-soluble polymer with a binary system forming a ternary one, on further enhancement of FBX solubility and dissolution rate. In vivo oral bioavailability was also studied using LC-MS/MS chromatography. The polymer screening study revealed a marked increment in the solubility of FBX with SBE7-βCD in the presence of 5% w/v polyethylene glycol (PEG 6000). In vitro release profile showed a significant increase in the dissolution rate of FBX from FBX ternary complex (FTC). Oral in vivo bioavailability of prepared FTC showed more than threefold enhancement in Cmax value (17.05 ± 2.6 µg/mL) compared to pure FBX Cmax value (5.013 ± 0.417 µg/mL) with 257% rise in bioavailability. In conclusion, the association of water-soluble polymers with FBX and SBE7-βCD system could significantly improve therapeutic applications of the drug.