The basic principle of tablet coating is relatively simple where the application of the coating substance on a moving bed of the tablet with simultaneous use of hot air to evaporate the solvent.
The pharmaceutical solid dosage form consists of tablets, capsules, pellets, granules, sachets, caplets, powders, and pills, of which the tablet is the most commonly prescribed and used dosage form. The tablets come in different types and are coated for several causes such as to mask the unpleasant taste, odor, and color of the API, to provide physical and chemical protection to the medicine, and to control the release rate of the drug.
What is a tablet-coating?
The coating is a highly advanced technique commonly used in pharmaceutical industries which is applied in several solid oral dosage forms such as tablets, capsules, and other solid dosage forms. Tablet coating is a method by which a thin layer of coating material is applied to the surface of a dosage form to get particular advantages.
Principle of tablet coating:
The tablet dosage forms are rotated continuously in a packed rotating-drum and coating material is automatically sprayed between the rotation according to process and parameters, at the same time hot air is supplied under negative pressure. The hot air enters through the core layers of the tablet so that the coating medium sprayed on the surface of the tablet cores will dry rapidly and uniformly, consequently creating a solid and smooth surface of the tablet.
Different types of tablet coating:
According to the nature and properties of different types of tablets, there are different types of coatings are used in pharmaceutical production.
1. Sugarcoating
2. Enteric coating
3. Film coating
4. Gelatin coating
5. Compression coating
6. Some other types of tablet coatings include dip coating, electrostatic coating, and rotary-die coating, etc.
Basic requirements of tablet coating:
- To ensure a uniform, smooth coating, tablets should be dust-free.
- Typically tablets to be coated are compressed with the punches and die set. This helps the applied coating material to easily cover the tablet.
- Core tablets have to be more rigid than uncoated tablets since they will have to withstand additional processing tasks.
- The material or solvent to be coated on the tablets needs to be inert.
Primary components involved in tablet coating:
The primary components involved in tablet coating are as follows.
1. Properties of the tablet
2. Coating process
3. Equipment used in coatings
4. Coating process parameters
5. Facility and ancillary apparatus
6. Automation in the process of coating
7. Coating composition
Objectives of tablet coating:
- The major objectives of tablet coatings are as follows.
- To mask the unpleasant taste and odor of the tablet
- To increase patient compliance
- To increase the mechanical strength of the dosage form
- To provide physical and chemical protection for medicine and protect the drug from external environmental conditions such as air, moisture, and light
- To include incompatible drugs together in a single tablet
- To protect the drug from release in the gastric environment of the stomach
- To make it easy to swallowing of large dosage forms
- To modify and/or control drug release from tablets by making a delayed-release and sustained-release products
Different types of tablet coating equipment:
Depending on the working principle, there are three types of equipment are used in the tablet coating.
1. Standard coating pan
2. Perforated coating pan
3. Fluidized-bed coater
Tablet coating defects:
Coated tablets face many problems compared to uncoated tablets, as they go through different stages during the coating process. Some common tablet coating defects are as follows.
- Blistering
- Blooming
- Blushing
- Chipping
- Color variation
- Cracking
- Infilling
- Orange Peel
- Picking and sticking
- Pitting
- Roughness
Steps involved in tablet coating:
Generally, the coating process involves the following steps:
- Batch identification and selection of recipe
- Loading or dispensing
- Warming
- Spraying
- Drying
- Cooling
- Unloading
Advantages of tablet coating:
- The major advantage of tablet coating is that it masks the unpleasant odor, taste, and color of the active pharmaceutical ingredients (API) and controls the drug release profile.
- It increases the stability of the product.
- The coating can also enhance the mechanical integrity.
- The coating creates a smooth finish on the tablet and makes it easy to swallow, especially for adults and children.
Disadvantages of tablet coating:
- The major disadvantage of tablet coating is that the process of coating is tedious and time-consuming, which makes it costly.
- Tablet coating can interfere with the pharmacodynamic properties of the formulation.
- Compared to other processes, it is a complex process, so a skilled person is needed to handle the instruments.
Commonly asked questions on tablet coating are as follows.
How many types of tablet coating are there?
Tablet coating has three major types such as sugar coating, film coating, and enteric coating, etc.
Why do we coat tablets?
The tablets are coated for several reasons such as it can control the release rate, protect the product from environmental conditions, and make the tablet easier to swallow, etc.
What is the difference between coated and uncoated tablets?
The major difference between coated and uncoated tablets is that the coated tablets have a thin layer of coating material is applied to the surface, whereas uncoated tablets don't require a special process after compression and are designed to provide rapid disintegration in the gastric fluid.
Which tablet coating is thin and dissolves rapidly?
The sugar coating on the surface of the tablet is finely coated and dissolves easily after swallowing.
What is tablet coating made from?
Tablet coating processes can include any mixtures of purified water, polymer, plasticizer, cellulose derivatives, colorants, polyvinyl, opacifiers, solvent, vehicle gums, and sugar, etc.
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