Sustained Release of Flufenamic Acid from a Drug-Triacetyl-β-Cyclodextrin Complex

Triacetyl-β-cyclodextrin (TA-β-CyD), a hydrophobic cyclodextrin derivative that is insoluble in water, was used to form a complex with flufenamic acid (FA). Complexes of FA with TA-β-CyD (FA-TA-β-CyD) at various molar ratios (1 : 1, 1 : 2, 1 : 3) were prepared by a kneading method, using ethanol as a solvent. FA-TA-β-CyD complex formation was demonstrated by differential scanning calorimetry and powder X-ray diffractometry. The release rate of FA from the FA-TA-β-CyD complexes was measured in both the Japanese Pharmacopoeia XII 1st fluid pH 1.2 and isotonic phosphate buffer pH 6.8. The release rate of FA from the FA-TA-β-CyD complexes in the isotonic phosphate buffer pH 6.8 was significantly retarded compared to the release rate of FA from the FA-glucose mixture. After 1 h, 100% of the drug was released from the FA-glucose mixture and 10-25% was released from the complexes. When either the powder of the FA-glucose mixture or the FA-TA-β-CyD mixture was administered directly into the intraduodenal lumen in rats, the plasma concentration of FA reached a maximum level within 40 min after administration. On the other hand, when the FA-TA-β-CyD complexes were administered into the intraduodenal lumen, the plasma concentration of FA did not show a sharp peak, but remained at a plateau level (10-18 μg/ml) for 6-8 h. An increased mean residence time of FA following FA-TA-β-CyD complexes administration was observed; however, the AUC0-10 for the FA-TA-β-CyD complexes showed no significant difference from that for the FA-TA-β-CyD mixture. These results indicate that TA-β-CyD may serve as a hydrophobic carrier in sustained-release preparations of FA.The drug-TA-β-CyD complexes may therefore be useful in oral administration to achieve prolonged action and reduced side effects.