Solvent-free formulations suitable for use as film coatings are described. Coatings are applied by spraying molten mixtures onto tablcts in a conventional coating pan. The ewects of a series of 17 additives on two representative basic formulations are evaluated. Results are presented relative to appearance, disintegration. friability, and uniformity. Desirable characteristics imparted by the additives may be easily selected from tables and used in the formulation of subsequent coating compositions. The concentration of shellac in the basic formulations was found to govern the rapidity of disintegration of the coatings regardless of additives. Of the additives evaluated, only castor oil, cocoa butter, and isopropyl myristate improved the basic formulations.
Keyphrases 0 Tablet coating-solvent-free shellac polyethylene glycol 4000 formulations, effects of 17 additives, molten mixture spraying 0 Shellac-polyethylene glycol 4000 solvent-free tablet film coatings-formulation, effects of 17 additives. molten mixture spraying Film coatings -formulation of solvent-free shellac - polyethylene glycol 4ooo films for molten mixture spraying of tablets. effect of 17 additives The use of coatings on tablets and pills is well documented. For example, "Remington's Pharmaceutical Sciences" lists a bibliography of 322 references pertaining to the subject (I). Those familiar with thc art of tablet coating are acquainted with the reasons for coating and advantages and disadvantages of the application methods.
Until recently, sugar coating was overwhelmingly preferred and it still provides tablets of exceptional esthetic qualities. But for reasons of economy, both with respect to labor and material costs, other methods have gained popularity. Film-type coatings, in particular, offcr reduced labor and material costs, are thin enough that embossed emblems are retained, mask tastes and odors, offer improved stability over sugar coatings, provide increased resistance to abrasion, and provide increased luster when compared to compressed tablets
Unfortunately, it is necessary that most newer film coatings be applied with the film-forming material dissolved or suspended in volatile solvents such as acetone, chloroform, and alcohol. While these solvents evaporate quickly and make it possible to completc the coating operation in a short period, they also have many disadvantages. These solvents evaporate quickly, necessitating the use of large quantities which are either lost completely during the drying cycle or are partially recovered with expensive recovery systems. Elaborate precautions are somctimcs ncccssary to protect against their inherent toxicity. The associated hazards of explosion and firc from local conccntrations of vapors also must not be ignored. Furthermore, it is sometimes necessary to alternate the coating applications with drying cycles, since the use of solvent tends to dissolve portions of the coating already applied, resulting in sticking and clumping of tablets in the coating pan.