Tablet coating is a process that applies a dry outer layer to tablets to confer benefits like masking taste or controlling drug release. There are several components to the coating process, including tablet properties, coating equipment and methods, and coating compositions. Common coating equipment includes standard coating pans, perforated pans, fluidized bed coaters, and various specialized systems like immersion tubes. Tablet properties like shape and surface smoothness influence the coating process. Coating is applied using spray systems while heated air facilitates drying.

1. PHR 221: Pharmaceutical Technology II
Course Teacher: Mohammad Nasir Uddin
Lecturer, Department of Pharmaceutical Sciences, NSU

2. Tablet Coating

3. Tablet Coating
Tablet coating is a process by which an essentially dry, outer layer
of coating material is applied to the surface of a dosage form in
order to confer specific benefits that broadly range from
facilitating product identification to modifying drug release from
the dosage forms.

4. Reasons for Tablet Coating……
 To mask the taste, odor or color of the drug
 To provide physical and chemical protection for the drug
 To control the release of the drug from the tablet
 To protect the drug from gastric environment of the stomach
with an acid-resistant enteric coating
 To incorporate another drug or formula adjuvant in the coating
to avoid chemical incompatibilities or to provide sequential
drug release
 To improve the pharmaceutical elegance by use of special
colors and contrasting printing

5. Components of Tablet Coating Process
Three primary components in tablet coating process….
 Tablet properties
 Coating process
 Coating equipment
 Parameters of the coating process
 Facility and ancillary equipment
 Automation in coating process
 Coating compositions

6. Tablet Properties
Tablets to be coated must possess following properties:
 Tablets must be resistant to abrasion and chipping.
 Tablets should have smooth surface for proper coating.
 The tablets must be in constant motion during the early drying
phase to prevent tablet agglomeration.
 The spherical shape of tablet is preferable for coating process.
This will allow the tablets to roll freely in the coating pan with
minimal tablet-to-tablet contact.

7. Coating Process
 Tablet coating is the application of a coating composition to a
moving bed of tablets with the concurrent use of heated air to
facilitate evaporation of the solvent.
 The distribution of the coating is accomplished by the movement
of the tablets are either perpendicular (coating pan) or vertical
(air suspension coater) to the application of the coating
composition.

8. Equipments for Tablet Coating
Standard (conventional)
coating pan
Perforated coating
pan
Fluidized bed (air
suspension) coater
Immersion
Sword System
Immersion Tube
System
Accela-Cota
System
Pellegrini Pan
System
Hi-Coater
Systems
Driacoater
System
Glatt Coater
System
Air Suspension
System

9. Standard (Conventional) Pan Systems
• It consists of a circular metal pan mounted somewhat angularly
on a stand. The pan is 8 to 60 inches in diameter and is rotated on
its horizontal axis by a motor.
• Heated air is directed into the pan and onto the tablet bed and
exhausted by means of ducts positioned through the front of the
pan.
• Coating solutions are applied by ladling or spraying the material
onto the tablet bed. Use of the atomizing systems to spray the
liquid coating material onto the tablets produces a faster, more
even distribution of the solution or suspension.

10. Standard coating pan

11. Pellegrini Pan System
• The first coating pan rotating on a
horizontal axis equipped with
tapered side walls and an integral
baffle system.
• It has a baffled pan and a diffuser
that distributes the drying air
uniformly over the tablet surface.

12. Immersion Sword System
• In this system, drying air is
introduced through a perforated
metal sword device that is
immersed in the tablet bed.
• The drying air flows upward from
the sword through the tablet bed.
Since the air is more intimately
mixed with the wetted tablets, a
more efficient drying environment
is provided.
• Coating solutions are applied by an
atomized spray system directed to
the surface of the rotating tablet
bed.

13. Immersion Tube System
• With this system, a tube is
immersed in the tablet bed.
• The tube delivers heated air and a
spray nozzle is built in the tip of
the tube.
• Coating solution is applied
simultaneously with the heated air
from the immersed tube.
• The drying air flows upward and is
exhausted by a conventional duct.

14. Perforated Pan Systems
• These equipments consist of perforated or partially perforated
drums that are rotated on their horizontal axis in an enclosed
housing.

15. Accela-Cota and Hi-coater Systems
• In both systems drying air is
directed into the drum, is passed
through the tablet bed and is
exhausted through the perforations
in the drum.
Accela-cota system
Hi-coater system

16. Driacoater System
• It introduces drying air through
hollow perforated ribs located
on the inside periphery of the
drum.
• The ribs dip into the bed as the
pan rotates.
• Drying air passes up and
fluidizes the tablet bed.
• Exhaust is from the back of the
pan.

17. Glatt Coater
• The Glatt coater is the latest
perforated pan coater to be
introduced in the industry.
• In the Glatt coater, drying air can be
directed from inside the drum
through the tablet bed and out an
exhaust duct; alternatively, with an
optional split chambered plenum,
drying air can be directed in the
reverse manner up through the drum
perforations for partial fluidization of
the tablet bed. Several airflow
configurations are possible.

18. Fluidized Bed Systems
• These are highly efficient drying systems.
• Fluidization of the tablet mass is achieved in columnar
chamber by the upward flow of drying air. The airflow is
controlled so that more air enters the center of the column,
causing the tablets to rise in the center. The movement of the
tablets is upward through the center of the chamber. They then
fall toward the chamber wall and move downward to re-enter
the air stream at the bottom of the chamber.
• Coating solutions are continuously applied from a spray nozzle
located at the bottom of the chamber or nozzles can also be
present at the upper region of the chamber.

19. Fluidized Bed Systems

20. Coating Process
Spray Application Systems
High pressure, airless Low pressure, air atomized

21. High Pressure, Airless System
• Liquid is pumped at high pressure (250 to 3000 pounds per
square inch gauge) through a small orifice (0.009 inch to 0.020
inch id) in the fluid nozzle which results in finely divided
spray.
• The degree of atomization is controlled by the fluid pressure,
the orifice size and the viscosity of the liquid.
• Because of the small orifice, suspended solids in the coating
composition must be finely milled or filtered to prevent orifice
blockage.

22. Low Pressure, Air Atomized System
• In this system, Liquid is pumped through a larger orifice (
0.020 inch to 0.060 inch id) at relatively low pressure (5 to 50
psig).
• Low pressure air (10 to 100 psig) contacts the liquid stream at
the tip of the atomizer and finely divided spray is produced.
• The degree of atomization is controlled by the fluid pressure,
the fluid cap orifice, the viscosity of the liquid, air pressure
and air cap design.