Preparation and Evaluation of Poly-γ-glutamic Acid Hydrogel Mixtures with Amlodipine Besylate: Effect on Ease of Swallowing and Taste Masking

The purpose of the study was to prepare a poly-γ-glutamic acid hydrogel (PGA gel), to evaluate physicochemical properties, its ease of swallowing using texture profile analysis (TPA) and its taste-masking effects on amlodipine besylate (AML) using the artificial taste sensor and human gustatory sensation testing. Using TPA, 0.5 and 1.0% (w/v) PGA gels in the absence of drug were within the range of acceptability for use in people with difficulty swallowing according to permission criteria published by the Japanese Consumers Affairs Agency. The elution of AML from prepared PGA gels was complete within an hour and the gel did not appear to influence the bioavailability of AML. The sensor output of the basic bitterness sensor AN0 in response to AML mixed with 0.5 and 1.0% PGA gels was suppressed to a significantly greater degree than AML mixed with 0.5 and 1.0% agar. In human gustatory sensation testing, 0.5 and 1.0% PGA gels containing AML showed a potent bitterness-suppressing effect. Finally, ¹H-NMR spectroscopic analysis was carried out to examine the mechanism of bitterness suppression when AML was mixed with PGA gel. The signals of the proton nearest to the nitrogen atom of AML shifted clearly upfield, suggesting an interaction between the amino group of AML and the carboxyl group of PGA gel. In conclusion, PGA gel is expected to be a useful excipient in formulations of AML, not only increasing ease of swallowing but also masking the bitterness of the basic drug.