Swelling and drug release behavior of tablets coated with aqueous hydroxypropyl methylcellulose phthalate (HPMCP) nanoparticles

Abstract

Organic solvent-based enteric coating technology using hydroxypropyl methyl cellulose phthalate (HPMCP) has been developed for many years due to low water solubility of HPMCP. In this work, aqueous HPMCP nanoparticles (HPMCP-NPs) were prepared by neutralization emulsification method using HPMCP powder and ammonium hydroxide (NH 4OH) in the absence of any organic solvent and emulsifier. Tablets for enteric use were coated with HPMCP-NP dispersions having different degree of neutralization that was manipulated by ion-exchange process. Disintegration and dissolution behavior of coated tablets were investigated using UV-visible spectrophotometer based on USP method (pH 1.2 and at 37 °C) and simulated intestinal fluid (pH 6.8 and at 37 °C for 60 min), respectively. The ion-exchange process, which was directly achieved by the protonation of dissociated carboxylic acid group of the aqueous HPMCP-NPs, was introduced as a useful way to control the release rate of drug and hydrophobic nature of HPMCP coating layer with a view for pharmaceutical application. The drug release and swelling were increased with increase in conductivity of aqueous HPMCP-NPs. On the other hand, particle size and polydispersity were decreased with increase in degree of neutralization.