INTRODUCTION TO PHARMACEUTICAL TABLET COATING:
In our last post on Tablet Compression, we did discuss a brief history of Pharmaceutical Tablets. As you may be aware, the tablets and pills are said to exists for more than thirty five centuries, however, may not be in the exact Or similar shape of the tablets Or pills as we currently use. Also, one of the theory suggests that the first reference to medicinal pills was found in ancient Egypt. 'Katapotia' was the popular name used for such medicinal pills in ancient Greece, which indicated that those pills were prepared for swallowing purpose, so as to gain the medicinal benefits.
One can imagine that such pills Or tablets formed manually would certainly be of odd shape Or may be of much bigger in size as compared to today's tablets and pills. Therefore, it must have been extremely challenging to consume (swallow) those medicinal pills and tablets. Needless to mention that the efforts must have been made to make it easy to swallow and hence the concept of coating the tablets Or pills with an easy going, easy tasting Or soft-greasy type and non harmful material must have originated.
Today, with advancement of science and technology, we find tablets with precise shape and mass with various types of coatings that makes the consumption easy and enjoyable.
POPULAR REASONS BEHIND COATING THE PHARMACEUTICAL TABLETS:
As against the ancient and medieval times, today there are a number of reasons for coating the Pharmaceutical Tablets. Some of them can be listed as under:
# To arrest and hold the bitter taste of the tablet inside the sweet coat
# To arrest and hold the unpleasant odor of the tablet inside the sweet coat
# To protect the tablet Or pill from the damage that can be caused during manual handling
# To avoid damage to the surface of the tablet Or pill due to any unwanted substance such as water, oil Or any other chemicals
# To protect the tablet from light or specific kind of rays of lights
# To provide overall protection to the tablet Or pill
# To avoid early disintegration of the tablet Or pill (say in mouth or throat itself before reaching further).
# To make it easily differentiable and for brand building purpose
THEORY BEHIND THE PROCESS OF COATING THE PHARMACEUTICAL TABLETS:
While the purpose of the coating is to offer protection and to increase the time required for the disintegration of the Tablet Or Pill, it has always been true to make the coat as precise and thin as possible, so that neither it makes the tablet Or pill useless, Nor does it alter its medicinal properties Or cause any harm to the consumer.
Keeping this in mind, the pharmaceutical Or nutraceutical Or Herbal medicine manufacturers need to overcome the challenges as under:
# Coating layer has to be uniform across all the tablets Or pills
# Coating layer has to be uniform within the surface of a tablet Or pill
# Coating layer should be so precise that it should melt Or dissolve at the right place (example say in gastrointestinal track or stomach etc) and at the right time.
# Coating layer should be harmless and under no condition should the coating material change its properties Or form any sort of bonding with the tablet mass
# Coating layer also brings an aesthetic appearance to the tablet. If not coated properly, sometimes the color variation makes it look non pleasing.
The popular types of coatings include sugar coating, film coating, enteric coating, controlled release coating, other Or specialized coating such as electrostatic coating, dip coating, compressed coating etc.
Let's discuss the commonly used equipments for coating purposes as follows:
COATING PAN:
Coating Pan is the most simplest and most commonly used coating equipment in the industry. Coating Pans varies in sizes ranging from 12" diameter (lab model) to 72" diameter (commercial model).
WORKING PRINCIPLE:
The Tablets Or Pellets or other items (to be coated) are added to the coating pan which is kept rotating at a low rpm. The coating solution is sprayed on the rotating items with the help of the spraying system while the pan is under rotation. A constant flow of hot air is applied over the mass so as to dry the film of coat faster.
MAJRO COMPONENTS OF A COATING PAN:
1. Coating Pan Or Bowl: It is an ellipsoidal pan which is meant to rotate across an axis which is tilted (ie at an angle of 45 degrees with the horizontal and the vertical plane) with the help of an AC motor. The speed of rotation is kept very low, so that the coating is effective without any damage to the tablets Or pellets.
2. Hot Air Blower: An attached Hot Air Blowing device is provided which contains an external centrifugal air blower driven by a high rpm AC motor, an inline set of electrical air heaters, set of inline air filters, a connecting duct (SS316 Or SS304) etc. The utility is to blow the hot air over the coating surface for drying it faster.
3. Spraying System: The Spraying system consist of a small agitated solution tank, a peristatic pump (AC motor driven), telescopic stand, Spray Gun and pneumatic fittings. The utility of the system is to spray the coating solution inside the coating pan with a regulated and constant speed.
4. Mountings: The system is mounted on a SS304 Or MS + Epoxy Painted stand, with Motor and Gear Drive supported (for coating pan).
5. Dust Extractor and Exhaust Blower: The exhaust assembly including the Dust Collector, Blower, Cyclone separator etc are optional.
6. Operating Panel: Either a Flame Proof Or Non-Flame Proof operating Panel with motor on-off and speed regulator controls are provided. The system can be optionally consists of a PLC and HMI too.
AUTO COATER:
Autocoater is a sophisticated and an automated version of a typical Coating Pan. As the name suggests, the manual steps involved in the operation of a Coating Pan are automated in this equipment.
FLUID BED COATER:
Unlike a Coating Pan Or an Auto- Coater, the Fluid Bed Coater works on the principle of Fluidization, where, the granules or pellets to be coater are fluidized in a FBP ie a Fluid Bed Processor. The coating solution is then sprayed into the FBP which forms a deposit on the external surface of each fluidized particle Or granule. The fluidization velocity and the spraying force is so maintained that we get the uniform coating on the granules and pallets.
Lets discuss a comparative Merits and Limitation of all these three equipments in the upcoming blog post.
Meanwhile, please feel free to contact incase of any queries, questions Or suggestions on this Or any other topic at shg.techo@gmail.com
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