Fabrication of delayed release hard capsule shells from zein/methacrylic acid copolymer blends

Hard capsule shells with an inherent delayed release action are useful for oral administration of active ingredients, which are acid-labile and/or enzymatically degradable in the gastric environment, without the need of film coating. The objective of this study was to fabricate delayed release hard capsule shells by the dip coating method. The film coating formulations comprised blends of zein and methacrylic acid copolymer (Eudragit® L100–55), with and without the addition of the plasticizer, polyethylene glycol 1000.

The rheology parameters (loss modulus (G’), storage modulus (G”) and loss tangent (tan δ, G”/G’)) of the film coating solution were measured to investigate the processability. Central composite design was used to investigate the main, interaction and quadratic effects of the proportion of methacrylic acid copolymer, solid content of the film formers and level of polyethylene glycol 1000 on the capsule wall thickness and mechanical strength. Multiple response optimization was further conducted, and the design space was established. The in vitro drug release in simulated gastric and intestinal fluids of three different formulations in the design space was compared. The results showed that the tan δ value after the gelation point should be < 0.9 in order to form a thin and sturdy capsule shell.

The gelation time and viscosity of the coating solution were related to the thickness of the capsule shell. The study showed that drug release from the capsule with a specified thickness and mechanical strength can be modulated by varying the ratio of zein to methacrylic acid copolymer. The delayed drug release profile was achieved through the capsule shell fabricated from zein to methacrylic acid copolymer at the ratios of 75:25 and 83.2:16.8, with 10% polyethylene glycol 1000.

Download the full article as a PDF here or read it here

Materials: Zein (α-zein, 14.0% of total nitrogen, Tokyo Chemical Industry Co., Ltd., Tokyo, Japan), methacrylic acid copolymer type C, or methacrylic acid/ethyl acrylate 1:1 copolymer (Eudragit® L100–55, Evonik Röhm GmbH, Darmstadt, Germany, supplied by Jebsen & Jessen Ingredients, Ltd., Bangkok, Thailand), polyethylene glycol with average molecular weight of 1000 (Merck, Darmstadt, Germany), magnesium nitrate hexahydrate (Merck, Darmstadt, Germany), pepsin (632 units/mg solid, Sigma-Aldrich, Missouri, USA) and pancreatin (1x USP specification, 25 units of protease activity, Merck, Germany) were used as received. Ethanol (95%v/v, pharmaceutical grade, Liquor Distillery Organization, Chachoengsao, Thailand) and deionized water were used as solvent. Diltiazem hydrochloride (Piramal Enterprises Ltd., Telangana, India, given by Siam Bheasach, Co., Ltd., Thailand) was used as a model drug in the in vitro drug release test. Other reagents used for assay and drug release studies were of analytical grade.

Article information: Yada Vattanagijyingyong, Poj Kulvanich, Jittima Chatchawalsaisin, Fabrication of delayed release hard capsule shells from zein/methacrylic acid copolymer blends, European Journal of Pharmaceutical Sciences, Volume 171, 2022. doi.org/10.1016/j.ejps.2022.106124.