Comparative Evaluation of Enteric Polymers (Eudragit L100-D55, HPMCAS-LF, And HPMCP HP-55) For Delayed-Release Duloxetine Hydrochloride Tablets

The objective of the present study was to comparatively evaluate different enteric polymers for the development of delayed-release duloxetine hydrochloride (duloxetine HCl) tablets. Duloxetine HCl is susceptible to degradation in gastric conditions, resulting in the formation of the toxic impurity α-naphthol; therefore, protection from gastric fluid is essential to ensure intestinal drug delivery. Four core tablet formulations were prepared by the direct compression method, and the formulation exhibiting rapid disintegration and optimal dissolution characteristics was selected for further coating studies. The selected core tablets were initially sub-coated with hydroxypropyl methylcellulose (HPMC K15M) to protect the drug core, followed by enteric coating using Eudragit L100-55, HPMCAS, and HPMCP polymers employing the ACG pan-coating technique. The prepared tablets were evaluated for pre-compression and post-compression parameters. Fourier transform infrared (FTIR) analysis confirmed the compatibility between duloxetine HCl and the selected excipients. In vitro dissolution studies demonstrated that all enteric-coated formulations effectively prevented drug release in acidic media, while enabling drug release in intestinal pH, with notable differences in release behavior among the polymers. Stability studies conducted at 0, 3, and 6 months indicated that the optimized formulation remained stable without any significant physical or chemical changes. The study concludes that the evaluated enteric polymers are suitable for delayed-release duloxetine HCl tablets, with comparative differences influencing release performance in intestinal conditions.