Studies On The Enhancing Effects Of Dimenthyl-β-cyclodextrin And Chitosan On Oral Bioavailability Of BMCP25

BMCP25 with poor aqueous solubility is a novel synthetic benzimidazole derivative which has anti-hepatitis B virus (HBV) activity. The purpose of the study is to develop the pharmaceutical formulation for enhancing oral bioavailability of BMCP25. BMPC25 was complexed to 2,6-di-O-methyl-beta-cyclodextrin (DM-β-CD). The enteric-coated capsules of BMCP25 with excipients were obtained. We investigated the enhancing effects of DM-β-CD and chitosan on oral bioavailability of BMCP25 in rats and rabbits.We established an accurate, sensitive and rapid high-performance liquid chromatography (HPLC) method to detect the concentration of BMCP25. The preformulation studies of BMCP25 include the solubility in water, other physical and chemical properties of BMCP25, for instance, the oil-water partition coefficient or the crystal surface of the drug are necessary. The inclusion complex of BMCP25/DM-β-CD was prepared in several moral ratio by kneading method and characterized. The dissolution test of BMCP25/DM-β-CD solid complexes were investigated. The dissolution profiles of BMCP25 and DM-β-CD Solid complexes shown dissolution rates were improved obviously, but the dissolution of BMCP25 alone was hardly detected and the solubility in water of BMCP25 was also significantly increased. Appropriate amount of inclusion complex and chitosan were filled in enteric-coated capsules by physical mixing method at the same equivalent. The prepared capsules consistent with the requirements of the 2010 edition of Chinese Pharmacopoeia standards, including content differences and disintegration.HPLC analysis was used to determine the plasma BMCP25 concentrations in rats or rabbits with a Diamonsil(?) C18 (250 mm×4.6μm,5μm) column and a mobile phase of methyl cyanides-water- formic acid (96/4/0.002) at a flow rate of 1 mL/min. UV detector was set at 216 nm. The detection limit of BMCP25 in both types of samples was 50 ng/mL. Linearity was observed over the concentration range 0.08-10μg/mL (R2=0.9999) in rat plasma and 0.05-10μg/mL (R2=0.9992) in rabbit plasma. The method recovery of quality control samples was 91.2-104.1%(rat) and 96.2-105.0%(rabbit). The relative standard deviations of intra-day were both less than 9.1% and the inter-day precision was less than 9.8% (rat) and less then 9.1%(rabbit). The samples were stable in both rat and rabbit plasma. The results obtained including linearity, linear range, recovery, precision, and accuracy were considered to meet the requirement for the analysis of biological samples. Male Sprague-Dawley rats were received a single dose of BMCP25 intravenous injection, BMCP25 and BMCP25/DM-β-CD solid complexes oral administration. New-Zealand White rabbits were subjected to BMCP25 intravenous injection, BMCP25 and the enteric-coated capsules. Blood samples were determined by HPLC and the profiles of BMCP25 concentrations in plasma vs time were obtained. The pharmacokinetic parameters were calculated using the Thermo Kinetica(?) software. the plasma concentration of BMCP25 could not be detected when the rats were oral gavaged BMCP25. The oral bioavailability of BMCP25 with DM-β-CD showed (16.84±5.88)% in rats. The oral bioavailability of BMCP25 with DM-β-CD and chitosan showed (46.52±9.62)% in rabbits.Using the Ussing Chamber technique, we investigated the enhancing effects of DM-β-CD and chitosan on the permeation of three drug transport markers (fluorescein and rhodamine123) across rat intestinal epithelium. The apparent permeability coefficient (Papp) of fluorescein was increased by 5% chitosan, with enhancemet ratio of 4.33. Under the influence of 10 mM DM-β-CD, the efflux ratio (ER) of rhodamine123 was decreased to 1.43. It had been shown that a synergistic effect between 10 mM DM-β-CD and 5% chitosan allowed a significant increase in Papp of fluorescein with enhancemet ratio of 8.89 (p<0.05) and lowered ER of rhodaminel23 from 3.62 to 1.19 (p<0.05). The association between DM-β-CD and chitosan would induce enhancing effect over the intestinal permeability of paracellular drugs and P-gp substrates. These results suggested that the enhancing effect of DM-β-CD and chitosan on the oral bioavailability of BMCP25 is due not only to solubilizing effect by DM-β-CD but also to a synergistic effect between DM-β-CD and chitosan on the permeation of BMCP25 from intestinal epithelial.