Adsorption of Amlodipine Besylate to Corn Starch and Microcrystalline Cellulose Suspended in Aqueous Solution

The adsorption of amlodipine besylate (AML) to microcrystalline cellulose (MCC) and corn starch suspended in aqueous solution was investigated herein. The adsorption of AML to experimental tools was assessed in a preliminary study, and the results obtained showed the adsorption of AML in water to glass, but not to polypropylene tools. Adsorption to glass tools was prevented by using 50% methanol solution. The adsorption isotherm of AML to MCC suspended in solution at 37˚C was the Langmuir type. Vmax, the adsorbed amount of drug per unit weight of MCC, and k, a constant, were 8.60×10−3 mmol/g MCC and 3.57 L/mmol, respectively. The adsorption isotherm of AML to corn starch suspended in solution at 37˚C was the Freundlich type. The Freundlich constants, k and 1/n were 0.729 and 3.57×10−3 mmol/g corn starch, respectively. The percent adsorption of AML to MCC and corn starch was lower in buffer and 0.9% NaCl solutions than in water. In buffer and 0.9% NaCl solutions, the percent adsorption to corn starch was higher than that to MCC. These results indicate that when the AML dissolution rate from orally disintegrating tablets in the mouth is the same, differences in the amount of corn starch in tablets affect the concentrations of solutions in the mouth due to adsorption. This difference may be detected by patients by a change in the taste of tablets.