The lansoprazole fast-disintegrating tablet (LFDT) is a new formulation developed as a rapidly disintegrating tablet containing enteric-coated microgranules. Three issues were considered in the development of LFDT. The first issue is damage to the enteric layer during the compression process, because the enteric-coated microgranules are compressed with a tablet press. In our previous study, 1) it was clarified that sufficient flexibility of the enteric layer was achieved by the optimized combined ratio of methacrylic acid copolymer dispersion to ethyl acrylate-methyl methacrylate copolymer dispersion and adding the optimized concentration of triethyl citrate to reduce the damage during the compression process. The second issue is the taste of LFDT. Since patients take LFDT after disintegration in the mouth, it was thought important to formulate LFDT with a pleasant taste. The third issue is the stability of lansoprazole in LFDT, because lansoprazole is incompatible with many excipients.The purpose of this study was to develop enteric-coated microgranules with an improved taste and the stabilization of lansoprazole. Since triethyl citrate has an unpleasant bitter taste and is an oily liquid, 2) it was anticipated that it would affect the taste of the enteric-coated microgranules and the stability of lansoprazole. Tabata et al. 3) reported that the degradation content of lansoprazole should be proportional to the product of the degradation rate constant and the total solubility of lansoprazole and suggested that lansoprazole in enteric dosage form would be unstable when it coexisted with a liquid and would be easy to dissolve. We studied the effects of triethyl citrate on the unpleasant bitter taste and stability of lansoprazole in enteric-coated microgranules and also attempted to formulate enteric-coated microgranules by masking the unpleasant bitter taste and improving the stability of lansoprazole. ExperimentalMaterials Lansoprazole was synthesized at Takeda Chemical Industries, Ltd. Commercial lansoprazole capsules were obtained in-house at Takeda Chemical Industries, Ltd.Lactose monohydrate-microcrystalline cellulose spheres (Nonpareil 105T, mean particle size 150-180 mm) and low-substituted hydroxypropyl cellulose (LH-33, hydroxypropoxy groups 5.0-6.9%) were kindly supplied by Freund Industrial Co., Ltd., and Shin-Etsu Chemical Co., Ltd., respectively. Methacrylic acid copolymer dispersion (Eudragit ® L30D-55) and ethyl acrylate-methyl methacrylate copolymer dispersion (Eudragit ® NE30D) were purchased from Rölm GmbH. Low-substituted hydroxypropyl cellulose (LH-32, hydroxypropoxy groups 7.0-9.9%) and hydroxypropyl methylcellulose 2910 (TC-5 EW) were purchased from Shin-Etsu Chemical Co., Ltd. Mannitol and polysorbate 80 were purchased from Merck Japan Ltd. Magnesium carbonate (Tomita Pharmaceutical Co., Ltd.), hydroxypropyl cellulose (HPC-SSL, Nippon Soda Co., Ltd.), talc (Matsumura Industrial Co., Ltd.), titanium dioxide (Freund Industrial Co., Ltd.), citric acid (A. D. M. Faryast, Ltd.), glyceryl monost...