Combination of a hot-melt subcoating and an enteric coating for moisture protection of hygroscopic Sennae fructus tablets

Abstract

The objective of this study was to investigate the efficiency of moisture protection of hot-melt coatings solely and in combination with an enteric coating on hygroscopic tablet cores containing a spray-dried Sennae fructus extract. Tablet cores were subcoated with different hot-melt coating materials: medium chain tryglycerides, stearic acid, Precirol^® ATO 5, and Compritol^® 888 ATO, at varying amounts and coated with Eudragit^® L 30D-55 for enteric resistance. Subcoating penetration, tablet disintegration, dissolution times, tablet hygroscopicity, and tablet properties such as weight, height, diameter, and hardness were analyzed. 3 mg/cm² of tablet surface seemed to be sufficient if sustained release is not required. Thereby, hot-melt coating did not adversely affect the tablet properties with regard to subsequent processing steps. Compared to the tablet cores it was possible to reduce the moisture uptake by 85% at 75% relative humidity with tablets coated with a combination of Precirol^® ATO 5 and Eudragit^® L 30D-55. This combination was more efficient than high amounts of Eudragit^® L 30D-55. Hot-melt coating proved to be a suitable technique for the application of subcoating material to tablet cores serving as a barrier against water permeation into hygroscopic tablet cores without exceeding the required disintegration times.

Keywords:

• Sennae fructus
• spray-dried extract
• hot-melt coating
• enteric coating
• moisture-sensitive tablets
• hygroscopicity
• disintegration time

Acknowledgements

The authors gratefully acknowledge the technical support and supply of materials by roha arzneimittel GmbH and Dr. P. Berghöfer for his helpful discussions. V. Nguyen is thanked for her assistance with hygroscopicity measurements and R. Walters for her support and patients during microscopic imaging.

Disclosure statement

No potential conflict of interest was reported by the authors.