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Books About Coating:

Pharmaceutical Coating Technology

Pharmaceutical Unit Operations: Coating (Drug, Manufacturing Technology, Series V.3)

 
1] What is Film Coating? Film coating is the process whereby a tablet, capsule, or pellet is surrounded by a thin layer of polymeric material. 
 
2) Reasons for film coating include:
Appearance To change the color, for branding purposes or other aesthetic reasons
Stability To protect the active ingredient from moisture, light, and/or the acidic environment of the stomach
Taste/odor  Masking To provide an easy to swallow tablet without the bitter taste of many actives
Release characteristics Many film coating materials have functional properties which enable the creation of sustained or delayed (enteric) release dosage forms
 
3) The basic components of a film coating system are:
polymer
Solvent 
plasticizer
optional ingredients:
anti-tack agent
anti-foam agent
colorant
filler/extender
flavorant
surfactant

4] Film coatings are available based on the following polymeric materials:     

 

Cellulose

 

Cellulose Acetate Phthalate

 

Hydroxypropylmethylcellulose

 

Hydroxypropylcellulose

 

Hydroxypropylethylcellulose

 

Ethylcellulose

 

Methylcellulose

 

Microcrystalline Cellulose and Carrageenan

 

Methacrylic acid/methacrylate esters

 

Anionic and Cationic polymers of Methacrylic Acid

 

Copolymers of methacrylates

Copolymers of Acrylates and Methacrylates

Copolymers of Ethacrylate and Methylmethacrylate

Polyvinylacetate phthalate

Shellac

 

Most of these materials are available as the individual powders, but many are also available in premixed powder blends, powder concentrates and aqueous dispersions.

 

Dry powder concentrates for reconstitution combine polymer, plasticizer and if desired, pigment in a  single system for either aqueous or organic coating procedures, which reduces inventory handling and raw material testing.

 

Aqueous based coating systems including the aqueous dispersions have become popular in recent years since they are solvenet free and more environmentally friendly. Most polymers are now available for reconstitution in water, or as an aqueous dispersion. 

 

Points to consider in the preparation and use of coating solution/dispersions:

 

Ensure complete and uniform dissolution/dispersion of all coating  ingredients throughout the coating process

Maintain viscosity of coating solution/dispersion throughout the coating process

Keep fluid lines free of any aggregates of solid material throughout the coating process.

Limit the amount of air entrapment/foam creation during coating solution/dispersion preparation and throughout the coating process

 

Products for Immediate Release include:

Cellulose-based coating materials

Methacrylate-based coating materials

Products for Sustained Release include:

Cellulose-based coating materials 

Methacrylate-based coating materials

Products for Enteric coating include:

Cellulose-based coating materials

Methacrylate-based coating materials

Shellac

 

Need a supplier? Submit in Excipients Express!!!

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5) Coating Processes and Equipment 

The majority of tablet film coating is performed in perforated closed system pans. These provide the necessary controlled conditions of temperature and air flow which enable reproducible and efficient application of both appearance and functional coatings. In addition, they limit operator exposure.

In choosing a system for film coating, the following points should be addressed:

Adequate supply of process air for the volume of the pan.
Ability to maintain temperature within a narrow range (typically 30 to 70șC).
Ability to maintain dew point within a narrow range (typically 10 - 20șC).
Pan and spray system designed to be easily cleaned/sanitized.
Spray system fluid path should have a minimum of dead spaces, since many coating formulations are dispersions or suspensions.
Spray system atomization and fan air are easily controlled, preferably from the exterior of the pan.
Air flow bypass capability (especially if the pan is to be used for sugar coating.
Explosion prevention construction if flammable solvents are to be used.
Treatment of Inlet and Exhaust Air as required by GMP and environmental regulations. 
 

The pan should be equipped with appropriate sensors so that the following conditions can be monitored/controlled:

Pan rotational speed
Inlet air temperature
Inlet air dew point
Inlet air flow rate
Spray system atomization and fan air flow rate
Coating liquid spray rate
Exhaust air temperature
Product temperature

 

Equipment Suppliers for perforated pans:

Iriam

LB Bohle

Nicomac

O'Hara Technologies, Inc.

Thomas Engineering

Vector Corporation

Werner and Mathis

Equipment Suppliers for fluid bed coating systems:

Fluid Air, Inc.

Glatt  

LB Bohle

 

Contract Coating Services  

Kali Pharmaceuticals  

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Pformulate/01/02/2003