Design and evaluation of double coated floating capsules based on gas formation

Abstract

The purpose of this work was to create double coated floating capsules using gas formation. Theophylline was used as a model drug. Theophylline and hydroxypropyl methylcellulose (HPMC) were physically blended and filled in hard capsules. Then, they were coated with a layer of a gas producing agent (NaHCO3) and a gas-entrapped membrane (i.e., EuRL30D, EuRS30D). The impact of types of gel-forming polymers, and gas-entrapped membrane's coating types and levels on floating characteristics and drug release from the floating capsules was investigated. Optimum formulations could float immediately and maintain buoyancy longer than 8 h. The increased viscosity of the high molecular weight HPMC in the floating capsules resulted in a delayed drug release, compared to the low molecular weight HPMC-containing capsules. The floating capsules coated with EuRS30D released the drug more slowly than those coated with EuRL30D. Due to EuRS30D demonstrated relatively low drug release, EuRL30D appeared to be a promising option for gas-entrapped membranes. Drug release was decreased as the gas-entrapped membrane's coating level was increased, resulting from a thicker film. The floating capsules with good floating abilities and sustained drug release were obtained in this investigation.