Classification of Tablet coating

Classification of Tablet Coating

Tablet coating is classified mainly into two types:

  • 1. Sugar coating
  • 2. Film coating
    • Sub division:
    1. Non-enteric coating
    2. Enteric coating

A. Sugar Coating

The major ingredient used in sugar coating is sugar, which may be substituted by other materials like sorbitol. Other additives used are as follows:

  1. Fillers: contains calcium carbonate, talc and titanium dioxide.
  2. Coloring agents: FD&C approved dyes and lakes.
  3. Film formers: Acacia, gelatin and cellulose derivatives.
  4. Anti-adherents: Talc and surfactants.
  5. Flavouring agents: Fruit and chocolate flavors.

Different stages of sugar coating

1. Seal coating:

  • Seal coating approach is used to cover (encapsulate) the core tablet with a layer of water-resistant polymer, preventing aqueous solvent from penetrating the core tablet during the primary coating phase.
  • The core tablets are placed into the coating pan, subjected to dedusting, mainly with cellulose acetate phthalate solution spraying, and drying before being finished.
  • The asbestos-free talc is applied on the seal-coated pills, and they are rotated for 3 to 5 minutes.
  • The machinery is turned off, and the tablets are dried for an hour while the exhaust is turned on and cool air is supplied.
  • Ingredients: Mainly Cellulose acetate phthalate, shellac, acetone and ethanol .

2. Sub-coating:

  • This Sub-coating process is done to advance the bond between seal coat and the sugar coat by means of water-soluble polymer.
  • The tablets are rotated and the sub-coating solution (like: acacia) is sprayed over the tablets after which the tablets are rotated for 15 min. with purified talc (if necessary)
  • Ingredients includes: Acacia, puri.water gelatin, Powder sugar cane.

3. Syruping:

The next three steps comprise this process :

  • Grossing:
    • The exhaust is turned “ON” before the pills are introduced. A 120 °F or such temperature of warm air is passed.
    • Sub-coating agents are present in the solution that is sprayed. The tablets are rolled for 15 to 30 minutes after coating.
    • Ingredients: Sub-coating agent, coloring agent, sugarcane powder and puri. water.
  • Heavy syrup:
    • In this step, the tablet gains the most weight. At a constant temperature and relative humidity, a syrup comprising a coloring ingredient and sugar cane powder is sprayed slowly and uniformly onto the tablets.
    • To ensure tackiness, the pills are totally dried.
    • Ingredients: Sugarcane powder, coloring agent and syrup.
  • Regular syrup:
    • In this step, distilled water is used to dissolve the colouring agent and sugar cane powder, which is then sprayed onto the tablet at a predetermined temperature.
    • The entire batch is then left overnight with the pan’s lid snugly shut.
    • Ingredients: Puri. water, colouring agent, and powdered sugarcane.
  • Polishing:
    • The coated tablets are rotated and the solution of polishing agents (like: bees wax) are sprinkled gradually and homogeneously, and after the process the tablets are rotated for a period of 30 min. by passing cold air in the machine.
    • Ingredients: White beeswax, carnauba wax, ethanol and acetone.

Advantages of Seal coating

  1. Patients generally accept sugar-coated pills.
  2. The raw resources are affordable and widely accessible.

Disadvantages of Seal coating

  1. The cost of packaging and delivery goes higher as a result of the finished product’s increased weight and size (up to 40% of the weight of its core tablet).
  2. It is a very tedious and time-consuming operation.
  3. No engraving or monogramming of the tablet is allowed.
  4. A highly trained coating operator is required.

B. Film Coating

The composition of a coating solution is explained in below Table,

Tablet Coating-Film Coating

Advantages of Film Coating

  • Reduction in coating time and material cost.
  • No significant rise in tablet weight.
  • Seal coating is not required.
  • No. of coating steps is less.
  • It resists cracking and chipping.

Disadvantages of Film Coating

  • It has a high risk of flammability hazards.
  • It will add concern over environmental pollution.

Methods of tablet coating

Methods of tablet coating are as follows:

  1. Pan coating
  2. Air suspension coating
  3. Dip coating
  4. Compression coating

Related: Enteric coated tablets


  • Tablet Coating – an overview | ScienceDirect Topics
  • Book: Arun S. Mujumdar (2015). Handbook of Industrial Drying. CRC Press, Taylor and Francis Group, New York.
  • Book: PHARMACEUTICAL ENGINEERING-Principles and Practice Unit Operations Abridged with PCI Syllabus of B. Pharmacy by C.V.S. Subrahmanyam, J. Thimmasetty, Mrs Sarasija Suresh and Mrs V. Kusum Devi

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