Correlation of surface characteristics with ease of production and in vitro release of sodium salicylate from various enteric coated microcapsules prepared by pan coating

Development and Comparison of Various Coated Hard Capsules Suitable for Enteric Administration to Small Patient Cohorts

Pharmaceutical technology offers several options for protecting substances from acidic environments, such as encapsulation in enteric capsules or dosage form with enteric coating. However, commercial enteric capsules do not always meet limits for pharmacopeial delayed release, and the coating process is generally challenging. Preparing small enteric batches suitable for clinical use is, therefore, an unsolved problem. This experiment offers a simple coating process of DRcaps^TM capsules based on hypromellose (HPMC) and gellan gum to achieve small intestine administration. In addition, DRcaps^TM capsules were compared to hard gelatin capsules to evaluate the suitability of the coating method. Both capsules were immersed in dispersions of Eudragit^® S 100, Acryl-EZE^®, and Cellacefate at concentrations of 10.0, 15.0, and 20.0% and dried. Coated capsules were evaluated by electron microscopy, disintegration, and dissolution test with a two-step pH change (from 1.2 to 6.8, then to 7.5) to simulate passage through the digestive tract. DRcaps^TM capsules coated with Eudragit^® S and Cellacefate achieved acid resistance. While samples coated with Eudragit^® S released their contents within 360 min at pH 6.8 (small intestine), regardless of polymer concentration, capsules with 15.0 and 20.0% coatings of Cellacefate released content at pH 7.5 (colon) within 435 and 495 min, respectively.

Effect of Alkali Treatment on Properties of Native Shellac and Stability of Hydrolyzed Shellac

The objective of this study was to investigate the effect of alkali treatment on properties of shellac. The native shellac was treated with sodium hydroxide for 15, 30, and 60 min to obtain hydrolyzed shellac. All types of shellac, namely native and hydrolyzed shellac at various times of treatment, were then prepared in films as free acid and ammonium salt forms by using ethanol and ammonium hydroxide solution, respectively. The results showed that alkali treatment caused an increase in acid value and a decrease in ester value. This is due to higher free carboxylic and hydroxyl groups caused by ester bond breaking. The longer the alkali treatment the higher impact of bond breaking, therefore, causing an increase in acid value, solubility at pH 7, strain, a decrease in ester value, water vapor permeability coefficient, and stress. The films were then kept at 40 degrees C, 75% RH for a period of three months. The aging effect led to an esterification of free carboxylic and hydroxyl groups, resulting in the significant change of acid value, ester value, and insoluble solid for both native and hydrolyzed shellac films in acid form. On the other hand, all types of shellac films in ammonium salt form exhibited a reasonable stability in physicochemical and mechanical properties as all films were protected from the esterification due to the formation of ammonium salt at the carboxylic binding site. It could be concluded that alkali treatment could produce hydrolyzed shellac with higher solubility in the intestine, the stability was yet in dilemma unless the shellac was in an ammonium salt form. The result obtained could, thus, provide a guideline in the use of shellac.

In vitro and in vivo evaluation of cellacephate microcapsules of sodium salicylate prepared by pan coating

Within various organic solvent based coating systems examined, one containing cellacephate and hydrogenated castor oil as cofilm formers was found to produce microcapsules of sodium salicylate by pan coating with optimum enteric properties, as determined by in vitro evaluation by scanning electron microscopy and dissolution studies. Scintiscans showed that such microcapsules packed in an outer hard gelatin capsule shell lodged temporarily in the oesophagus and tended to form aggregates on liberation in the stomach of the dog. Because of their rapid clearance from the stomach, single dosage with these microcapsules only prolonged appearance of the plasma peak by about 1.5 h in comparison to a conventional form. The microcapsules showed no decrease in bioavailability and only slight faecal blood loss during acute toxicity testing for gastrointestinal bleeding.