Tablet coating1

PHR 221: Pharmaceutical Technology II

Course Teacher: Mohammad Nasir Uddin

Lecturer, Department of Pharmaceutical Sciences, NSU

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.

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

Reasons for Tablet Coating……

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

Components of Tablet Coating Process

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.

Tablet Properties

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.

Equipments for Tablet Coating

Standard (conventional)

coating pan

Perforated coating

panFluidized bed (air

suspension) coater

Immersion

Sword System

Immersion Tube

System

Accela-Cota

System

Pellegrini Pan

System

Driacoater

System

Glatt Coater

System

Hi-Coater

Systems

Air Suspension

System

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.

Standard coating pan

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.

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.

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.

Perforated Pan Systems

• These equipments consist of perforated or partially perforated

drums that are rotated on their horizontal axis in an enclosed

housing.

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

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.

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.

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.

Fluidized Bed Systems

Coating Process

Spray Application Systems

High pressure, airless Low pressure, air atomized

High Pressure, Airless System

• Liquid is pumped at high pressure (250 to 3000 pounds persquare inch gauge) through a small orifice (0.009 inch to 0.020inch id) in the fluid nozzle which results in finely dividedspray.

• 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 coatingcomposition must be finely milled or filtered to prevent orificeblockage.

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.