Preparation of HPMC/Pectin-Coated Systems for Oral Colon delivery

Purpose The project here presented concerns the preparation of coated systems in which the targeted release in the colon is ensured by the combination of the degradation of the coat, by enzymes present in this region (microbiological approach) and the time required for the erosion and dissolution of the coating layer (time-dependent approach). To achieve such a release, the systems will require a coat composed primarily of a biodegradable polymer (pectin) and hydrophilic swellable polymers (HPMC). Methods Tablets containing 65mg of acetaminophen as the model drug were prepared with a rotary press (concave punches, diameter and curvature radius 5mm). The viscosity of the coating solutions was measured using a rotating viscosimeter on a range of shear stress 0-500/s. High- and low-methoxylated pectins (Cesapectin LM32, HMSS) were tested alone and in mixture with low viscosity HPMC (Methocel E50). Spray coating processes were carried out employing a 10 L coating pan equipped with a two-fluid nebulizer. Release tests on coated systems were performed in an adapted disintegration apparatus (DT6, Logica Progetti) placing one single unit in each basket rack (800mL, 37.0±0.5°C, n=6). Purified water, phosphate buffer 6.8 and HCl 0.1N were employed as dissolution media. Enzymatic degradation was simulated in vitro by the addition of 1mL pectinase (Pectinex). Fluid samples were withdrawn automatically at fixed times and acetaminophen was quantified spectrophotometrically. Results Based on the viscosity studies and on preliminary tests performed on the preparation of isolated films, the concentration for each aqueous HPMC/pectin solution was chosen for the spray coating process. The operating conditions were selected in order to achieve the desired final product in terms of yield and morphological characteristics. Samples were collected and characterized at increasing coating levels. The systems were capable of retarding the release of acetaminophen by increasing lag time proportionally to the applied coating layer and depending on its composition. Conclusion The assessment of the release profile of acetaminophen from HPMC/pectin-coated tablets indicates the possibility of controlling the release based on the coating levels and composition of the layer added to the cores.