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• Asif Hasan Niloy

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INDUSTRIAL PHARMACY

Tablet coating

COATING: Coating is a process by which a thin-film polymer is applied on granules or tablets to confer specific benefits. It is applied to a wide range of oral dosage forms. REASON FOR COATING: 1. Protecting the drug from its surrounding environment in order to improve stability. 2. Masking unpleasant taste and odor. 3. Improving product identity 4. Improving product appearance. 5. Reducing the risk of interaction between incompatible components. 6. To control release. 7. Modifying drug release, as in enteric coated, repeat action, sustained release products. MAIN COATING PROCESS:

BRAND NAME OF COATING MACHINES:

 Sugar coating

 Accela cota.

 Film coating

 Hi-couter

 Compress coating

 Driacoater

 Microencapsulation

 Glatt coater

CORE TABLET: The tablet which is coated is called core tablet. Sugar Coating Successive application sucrose based solution to coat a tablet by using suitable coating equipment. The sugar coating process follows six main steps: 1. Sealing or water proofing: Objective: To provide moisture barrier into the tablet core. Without it, tablets would absorb excess moisture, leading to tablet softening or disintegration and affecting the physical and chemical stability of the finished product. Common materials used as a sealant include – Shellac, Zine, Cellulose acetate phthalate (CAP), Hyroxylpropylcellulose, Hyroxypropylmethylcellulose etc 2. Sub coating: it causes a rapid buildup tablet size and round of the tablet edges. Gelatin, gum acasia, calcium carbonate is the example.

Md. Asif Hasan Niloy

5th Semester

24 BATCH

|

1

Tablet coating Course Instructor: MD.SELIM HOSSAIN

3. Smoothing: It is done to make elegant of the sub-coating. Smoothing usually can be accomplished by the application of a simple syrup solution (approximately 60-70 % sugar solid). This syrup generally contains pigments, starch, gelatin, acacia or opacifier if required. 4. Coloring: gives the tablet its color and finished size. The types of coloring materials used can be divided into two categories – water soluble dyes or water insoluble pigments. 5. Polishing: produces the gloss. Characteristics of the tablet. Polishing is achieved by applying the mixture of waxes like beeswax, carnubawax, candelila wax or hard paraffin wax to tablets in polishing pan. Film Coating Film coating can be defined as the polymer based thin film over the core tablet. It is the more common contemporary and thus commonly used process for coating oral solid dosage forms. Components: A. Polymer: The ideal characteristics of film coating polymers are – (1) Solubility: High water solubility is desired for film coating polymers. (2) Viscosity: Low viscosity is required for trouble free processing. (3) Permeability: Should be water impermeable. Polymer should have low permeability against water, oxygen if environmental protection is desirable. (4) Mechanical Properties: Should have enough strength to with stand the stress encounter during normal handling, packaging, transportation and storage of the tablet. Widely used polymers in the industries: 1. Cellulose derivatives. 2. Hydroxy propyl methyl cellulose (polar) 3. Methyl cellulose.

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4. Hydroxy propyl cellulose (HPC) 5. Carboxy methyl cellulose (CMC)

Md. Asif Hasan Niloy

5th Semester

24 BATCH

Industrial Pharmacy

Tablet coating Course Instructor: MD.SELIM HOSSAIN

6. Providon 7. Co-polymer of methacrylic acid derivatives (commercial name: Eudragit) B. Plasticizer: (1) Used to maintain elasticity. (2) Usually decrease thin brittleness. (3) It is effective in low concentration. Examples: Polyethylene glycol (PEG 400) Diethyl phthalate Coconut oil. C. Colorants: Usually water soluble colorants are used. Example: Iron oxide (Red, Yellow, Black) Titanium oxide (white) D. Solvents: Water or organic solvents are used to dissolve the components of coating formulation. The solvent act as a carrier for bringing the polymer over the tablet. The solvent is removed by drying. Water based coating formulation are prepared over organic based coating formulation because of two reasons. a. Organic solvents are toxic and b. Organic solvents are environmentally hazardous. Enteric Coating This technique is used to protect the tablet core from disintegration in the acid environment of the stomach. The coating we readily dissolve at the intestinal pH and liberate the drug from the tablet. Reasons: 1. Prevention of acid attack on API. E.g. enzymes. 2. To protect the stomach from the irritant effect from certain drugs like sodium salicylate. 3. To facilate absorption of a drug. 4. To deliver drugs intended for local actions in the intestine 5. To provide a delayed-release component for repeat action tablet.

Md. Asif Hasan Niloy

5th Semester

24 BATCH

Industrial Pharmacy

33

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Tablet coating Course Instructor: MD.SELIM HOSSAIN

Example: 1. Shellac but it is now avoid because it is responsible for growing of microorganism. 2. Cellulose acetate phthalate (CAP) 3. Polyvinyl acetate phthalate (PVAP) 4. Eudragit. All of this components have - COOH group, which is acidic in nature. For this reason drugs not release in stomach. In intestine drugs releases because stomach is basic in nature. Difference between sugar coating and film coating tablet. Subject

Sugar coating tablet

Film coating tablet

1. Appearance

Round with high degree

Return original coat of the

of polish coating.

tablet.

30 to 50%

2 to 3%

3. Logo/Break line

Not possible.

Is possible.

4. Stages

Multi stage process.

Single stage process.

5. Batch coating time

8 hours or longer

1.5 to 2 hours

6. Sustain or control

Usually not possible

Easily possible.

2. Weight

increase

due

coating

to

materials

release 7. Coating

of

granules

Possible

but

not

Possible and applied effectively

beneficial for industries.

in case of film coating.

Problems encountered with coating –  Twinning: Two tablets stick together, usually after becoming aligned along flat surfaces. Most common in capsule shaped tablets. Causes – Coating suspension cannot be evaporated. Remedy – Drying properly.

Md. Asif Hasan Niloy

5th Semester

24 BATCH

Industrial Pharmacy

44

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Tablet coating Course Instructor: MD.SELIM HOSSAIN

Reducing spray rate. Increasing pan speed.  Orange peel: It is surface defect resulting in film being rough or nonglossy. Appearance is similar to that of orange. Reasons – Inadequate spreading of the coating solution before drying. Remedy – Use additional solvents to decrease the viscosity of the solution.  Picking and Sticking: It is defect where isolated areas of film are pulled away from the surface when the tablet sticks together and then part. Picking does not occur alone it must have another tablet to be struck with which called sticking. Causes– Inefficient drying. Higher rate of application of coating solution. Over wetting Remedy – Use optimum and efficient drying conditions. Reduce liquid application rate.  Blistering: It is local detachment of film from the substrate forming blister Reason: Entrapment of gases in or underneath the film due to overheating either during spraying or at the end of the coating run. Remedy: Use mild drying conditions.  Colour variation: A defect which involves variation in colour of the film. Reason: Improper mixing Uneven spray pattern Insufficient coating. Remedy: Use of lake dyes eliminates dye migration.  Cracking: Small, fine cracks observed on the upper and lower central surface of tablets, or very rarely on the sidewall are referred to as cracks. Reason: Use of higher molecular weight m Higher internal stresses in the film.

Md. Asif Hasan Niloy

5th Semester

24 BATCH

Industrial Pharmacy

55

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Tablet coating Course Instructor: MD.SELIM HOSSAIN

Remedy: Use low molecular weight polymers and adjust the plasticizer and pigment types and concentration to minimize the internal stress Facilities for coating: (1) System of producing tablet bed movement: It must be good for moving a tablet easily. (2) Spraying system for coating solution: Use atomizer to spray cooling solution. (3) Hot air system: To remove the solvent, hot air is used. (4) Exhaust system: This is needed to expel out the evaporated solvent along with the used air and dust particles.

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Md. Asif Hasan Niloy

5th Semester

24 BATCH

Industrial Pharmacy