Basics Of Tablet Coating

Tablet coating is an essential step to be followed once a good tablet has been made. Coating of tablets is an important task because of its multiple benefits. Coating tablets will help in strengthening the tablet, control its release, improve its taste, color it, make it easy to handle and pack, and also protect it from moisture. In this article, tablet coating basics are described. There are numerous ways with which tablets can be coated but, sugar coating is amongst the earliest methods. This tablet coating process is still used in confectionery industry.

 

Different types of tablet coating methods include wurster coating, fluid-bed coating and dry coating. The most common method of applying coating to pharmaceutical tablets is called the film coating. Film coating is a combination of solids and liquids. Earlier liquid component was usually a volatile solvent like alcohol or any quick drying substance like methylene chloride. Though solvent based coatings performed well in all aspects, but they created trouble in handling, operator safety, recovery and odor. They often made the finished tablets smell like solvent, which gives an undesirable effect.

Before coating a tablet it is important to ensure that the tablet is of high quality and tough, so that it does not get damaged when coated and dried. The coating process becomes much simple if the tablet is consistent. Solvent based coatings have been replaced by water based(also known as aqueous) coatings. Water based coatings have resulted in making the coating process much more complexed.  Coating must be applied and water must be removed before the finish of the tablet gets hampered. Latest tablet coating machine include components like tablet coating pan, spraying system, air handling unit, dust collector and other controls. Coating pan is a drum with holes which rotates inside the cabinet.

Tablet coating is a complex process, wherein spraying, coating distribution and drying occur at same time. Some important points which one must know before starting the pill coating process are described below