Manufacture of Pharmaceutical Tablet Coatings

Pharmaceutical tablet coatings generally consist of a sugar or cellulose based binder, plasticizer, film forming agent and colorant. These ingredients are supplied in granulated or powder form for dispersion in aqueous or organic solvents at concentration varying from 10 - 20% depending on the desired coating properties and formula. In addition to enhancing the appearance and aiding identification of the product, tablet coatings perform a number of functions:

• To protect the tablet from moisture and other adverse conditions.
• To lubricate the tablet to ease swallowing.
• To disguise unpleasant tastes.
• To create a barrier between the active ingredient and the gastrointestinal tract.
• To control the release of drug into the body.

 

 

The Process

A typical method of dispersion is as follows:

• The water/solvent is charged into the mixing vessel, with the mixer positioned off center to create a vortex.
• The dry ingredients are added and drawn into the vortex.
• Mixing continues until the ingredients are fully dissolved.
• The finished coating is applied to the tablets by spraying in coating pans.

 

In order to achieve the above, a number of processing factors must be considered:

• The mixer must be capable of circulating the entire contents of the vessel to ensure uniformity.
• A wide range of colors are used in tablet coatings and batch sizes are generally small.
• Equipment must be easily cleaned and ideally adapted to be Cleaned-In-Place (CIP).
• The mixer must be capable of processing at ambient temperatures as some ingredients may be heat sensitive.