Abstract
The objective of this study was to determine whether a correlation exists between in vitro release and oral bioavailability of diltiazem (DTZ) in the delayed-release preparations. O-Carboxymethyl- O-ethyl-β-cyclodextrin (CME-β-CyD) was used as a delayed-release carrier. In vitro release rates were measured by a pH-changeable dissolution testing apparatus controlled by personal computer. Taking into account the physiological pH of gastrointestinal fluids, various release patterns of DTZ were generated by changing pH of the dissolution medium. For in vivo testing animal model, the gastric pH of fasting beagle dogs was controlled to obtain high acidity level (less than pH 2.0) and low acidity level (higher than pH 6.0) by the treatments of tetragastrin and omeprazole, respectively. The in vitro release rate of DTZ from tablets of its CME-β-CyD complex was accelerated with increasing pH of the dissolution medium. The in vivo absorption of DTZ after oral administration of the CME-β-CyD complex was retarded in the high gastric acidity dogs, while the fast absorption of DTZ was observed in the low gastric acidity dogs. In the CME-β-CyD complex, a good in vitro-in vivo correlation was observed for both gastric pH controlled dogs. The present results suggest that CME-β-CyD can serve as delayed-release carrier for water-soluble drugs.
Published Version
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