Abstract
Conventional enteric coating requires the use of organic based polymers which are equally hazardous to the environment and operating personnel. Hot-melt coating avoids the use of solvents and is a safer and time-saving process. The present study was designed to assess the efficacy of hot-melt coating (HMC) as an enteric coating technique. Pellets prepared by extrusion spheronization were selected as the core formulation for a model of the gastric irritant drug diclofenac sodium (DFS) because of their innate advantages over single-unit formulations. Stearic acid (SA) and palmitic acid (PA) were evaluated as enteric hot-melt coating materials. HMC was carried out in a specially modified coating pan by applying SA and PA in molten state onto preheated pellets to achieve a coating level of 5-15 %w/w. Hot-melt coated pellets were evaluated for disintegration pH and in vitro dissolution in the pH range 1.2 to 6.8, along with basic micromeritics. SEM of coated pellets showed a uniform and smooth coating. These results indicated that HMC of both SA and PA exhibited very good enteric coating ability. The coated pellets showed negligible drug release in acidic pH. As the pellets were subsequently transferred to a higher pH level, a gradual increase in release of the drug from the pellets was observed with increasing pH of the dissolution media. The release was dependent upon coating extent, providing sustained enteric release as opposed to abrupt release with mixed release kinetics.
Highlights
Enteric-coated dosage forms are designed to resist the acidic environment of the stomach and disintegrate in the higher pH environment of the intestinal fluid
The application of the hot-melt coating of Stearic acid (SA) and palmitic acid (PA) resulted in further improvement of these properties
The pellets had very good uniformity as desired and all formulations were within the size range of 800 to 1000 μ after hot-melt coating and exhibited a shape approaching that of a sphere
Summary
Enteric-coated dosage forms are designed to resist the acidic environment of the stomach and disintegrate in the higher pH environment of the intestinal fluid. The main reasons for using an enteric coating are to protect the stomach wall from the harmful effect of the drug in a dosage form (Petroski, 1989) or to prevent degradation of the drug by gastric contents (Levine et al, 1990). Upon entering the higher pH environment of the duodenum, the coating is dissolved, and the drug becomes available for absorption. Such a coating provides protection for the gut mucosa when the drug is capable of producing gastric distress or nausea due to irritation. Enteric coating can be used to deliver the active ingredients that are optimally absorbed from a particular region of the intestine, e.g. to the upper part of the small intestine, so as to enhance the bioavailability of the drug
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