Influences of sodium carbonate on physicochemical properties of lansoprazole in designed multiple coating pellets.

Lansoprazole (LSP), a proton-pump inhibitor, belongs to class II drug. It is especially instable to heat, light, and acidic media, indicating that fabrication of a formulation stabilizing the drug is difficult. The addition of alkaline stabilizer is the most powerful method to protect the drug in solid formulations under detrimental environment. The purpose of the study was to characterize the designed multiple coating pellets of LSP containing an alkaline stabilizer (sodium carbonate) and assess the effect of the stabilizer on the physicochemical properties of the drug. The coated pellets were prepared by layer-layer film coating with a fluid-bed coater. In vitro release and acid-resistance studies were carried out in simulated gastric fluid and simulated intestinal fluid, respectively. Furthermore, the moisture-uptake test was performed to evaluate the influence of sodium carbonate on the drug stability. The results indicate that the drug exists in the amorphous state or small (nanometer size) particles without crystallization even after storage at 40°C/75% for 5 months. The addition of sodium carbonate to the pellet protects the drug from degradation in simulated gastric fluid in a dose-dependent manner. The moisture absorbed into the pellets has a detrimental effect on the drug stability. The extent of drug degradation is directly correlated with the content of moisture absorption. In conclusion, these results suggest that the presence of sodium carbonate influence the physicochemical properties of LSP, and the designed multiple coating pellets enhance the drug stability.