Effect of sugar-modified beta-cyclodextrins on dissolution and absorption characteristics of phenytoin

Inclusion complexes of phenytoin (DPH) with 6-O-alpha-D-glucosyl (G1)- and 6-O-alpha-D-maltosyl (G2)-beta-cyclodextrins (beta-CyDs) were prepared in a molecular mixing ratio of 1:1. The advantages of these preparations in terms of dissolution characteristics and the oral absorbency of DPH were evaluated in comparison with the known solid dispersions of polyvinylpyrrolidone K-30 and sodium deoxycholate (DC-Na). The results of a phase-solubility study indicated that G1- and G2-beta-CyDs provided higher solubility for DPH than 2-hydroxypropyl (HP)-beta-CyD. Irrespective of inclusion ability, the DPH/beta-CyD complexes allowed faster dissolution rates than those of the known dispersions in JP 1st and 2nd mediums. The dissolution behavior of the DPH/DC-Na dispersion was considerably different between the 1st and 2nd mediums. The complexation by the sugar-modified derivatives yielded a higher stability of dissolved DPH in the JP 2nd medium than that yielded by K-30 or DC-Na. The safe estimation of carriers themselves indicated that G1- and G2-bet-CyDs did not damage the small intestine, while 10 mM DC-Na showed some damage. Compared with the DPH/K-30 dispersion, the preparations with the sugar-modified beta-CyDs were more effective in enhancing the absorbability of DPH after oral administration. These results clearly suggest that complexation with G1- and G2-beta-CyDs are useful forms for the oral delivery of DPH. The advantage of these complexes is that they produce an increased level of DPH available for gastrointestinal absorption. Additionally, G2-beta-CyD is recommended as a safe and potent additive for DPH.