Lecture notes
What is tables and coating of tablets ?
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Tablets, coating, methods, process, machines, dyes, etc are included in this.
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11/5/2017Contents
• Characteristics, advantages and disadvantages.
• Types of tablets, excipients.
• Granulation methods and machinery involved.
• Tablet compression operation-single punch and rotary tablet
Tablets & Coating of Tablets presses.
Dr. Sarath chandran C, Ph.D
• Processing problems, evaluation, packaging.
Assistant Professor
• Types of coating-sugar coating, film coating, compression coating,
Department of Pharmaceutics
electrostatic and enteric coating.
Email: scshenoy@gmail.com
• Film forming materials, formulation of coating solution.
• Equipments for coating.
• Processing problems in coating, evaluation.
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• Oral route of is the most preferred mode of drug administration.
– At least 90% of all drugs used to produce systemic effects are • Liquid dosage forms are preferred under following conditions
administered by oral route.
• Solid dosage forms are preferred class of products for oral
– The liquid form is what public has come to expect for certain
administration.
types of products (Eg: Cough medicines).
– Tablets & capsules are unit dosage forms in which drug is
precisely placed.
– The product is more effective in liquid form (Eg: Many
– Liquid dosage forms, dose fixation/accuracy is difficult.
adsorbents and antacids).
– Liquid dosage forms are more expensive to ship.
– The possibility for breakage or leakage during transporting is – The drugs are used fairly common by young children or the
more in case of Liquid dosage forms.
elderly, who have trouble swallowing the solid oral dosage
– Liquid dosage forms occupy more space in Pharmacy shelf!! forms.
– Taste masking is difficult task in liquid dosage forms.
– Drugs are more stable in dehydrated state.
– Liquid dosage forms may entertain microbial growth faster.
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Advantages of tablets
• They may provide the greatest ease of swallowing with the
• They are unit dosage form and they offer the greatest least tendency for hang-up above the stomach, especially
capabilities of all oral dosage forms for the greatest dose when coated, provided that tablet disintegration is in not
precession and least content variability. excessively rapid.
• Their cost is lowest of all oral dosage forms.
• They are the lightest and most compact of all oral dosage • They lend themselves to certain special release profile
forms. products such as enteric or delayed release products.
• They are the easiest and cheapest to package and ship of all
oral dosage forms.
• They are better suited to large scale production than other
• Product identification is potentially the simplest and cheapest unit oral forms.
requiring no additional processing steps when employing an
embossed or monogrammed punch face.
• They have the best combined properties of chemical,
mechanical and microbiologic stability of all the oral forms.
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Disadvantages Ideal properties of tablets
• Some drugs resist compression into dense compacts, owing • It should be a elegant product having its own identity while
to their amorphous nature or flocculent, low density being free of defects such as chips, cracks, discoloration,
character. contamination.
• It should have the strength to withstand the rigors of
• Drugs with poor wetting, slow dissolution properties, mechanical shocks encountered in its production,
intermediate to large dosages, optimum absorption high in packaging, shipping and dispensing.
GIT or any combination of these factors may be difficult to • It should have the chemical and physical stability to maintain
formulate as tablet. its physical attributes over time.
• It must be able to release the medicinal agents in the body
• Bitter tasting drugs, drugs with an objectionable odor or drugs in a predictable and reproducible manner.
that are sensitive to oxygen or atmospheric moisture may • It must have suitable chemical stability over time so as not
require encapsulation or entrapment prior to compression or to allow alteration of medicinal agents.
may require coating causing hike in cost of production.
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Types and Classes of Tablets
• Tablets Administered by Other Routes
• Tablets Ingested Orally – Implantation Tablets.
– Compressed tablets or Standard Compressed Tablets. – Vaginal Tablets.
– Multiple Compressed Tablets.
– Delayed Action and Enteric Coated Tablets. • Tablets Used to Prepare Solutions
– Sugar and Chocolate coated Tablets. – Effervescent Tablets.
– Film- Coated Tablets. – Dispensing Tablets (DT).
– Chewable Tablets. – Hypodermic Tablets (HT).
– Controlled Release Tablets – Tablet Triturates (TT).
• Tablets Used in the Oral Cavity
– Buccal and Sublingual Tablets.
– Troches and Lozenges.
– Dental Cones.
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Tablets Ingested Orally
– Tablets of this category are prepared for one of the two reasons i.e., to
• Compressed Tablets or Standard Compressed Tablets separate physically or incompatible ingredients or to produce repeat
action or prolonged action tablets.
– Manufactures either by Wet granulation, Double compaction or Direct
compression. – The layered tablet is preferred to the compression-coated tablet;
– Tablets provide rapid disintegration and drug release. surface contact between layers is lessened and production is simpler
– Drugs (Water insoluble, especially of antacid and adsorbent category) and more rapid.
produce local effect in GIT area with definite level of aqueous solubility – In MCT, one of the layers will be able to produce a initial drug release
to cause absorption in the body. in stomach and the other layer may release the drug in intestinal
environment.
• Multiple Compressed Tablets
– Gastric emptying rate may affect the drug-plasma profile.
– Two classes of MCT i.e., Layered Tablets and Compression Coated
Tablets.
– Both may be two or three component system. i.e., 2 or 3 layered
tablets (Tablet within the Tablet or Tablet within the Tablet within the
Tablet).
– They undergo initial light compression followed by heavy final
compression.
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• Repeat-Action Tablets • Delayed- Action and Enteric Coated Tablets
– Depends upon uncontrolled and unpredictable gastric – DA tablet release the drug at delayed rate after it passes from part of
emptying. GIT to another.
– MCT and Sugar coated tablets may be used. – The enteric coated (EC) is the best example.
– All EC tablets are type of DA tablets but all DA tablets are not EC.
– The core tablet is usually coated with shellac or an enteric
– The coatings used are primarily mixed acid functionality and acid ester
polymer so that it will not release its drug load in stomach. functionality with synthetic or modified natural polymers.
– The second dose of the drug is then added in the sugar – Cellulose Acetate Phthalate (CAP) used commonly.
coating, either in solution in the sugar syrup or as part of – Polyvinyl Acetate Phthalate and Hydroxypropyl methylcellulose
the dusting powder added for rapid coat build up. Phthalate are also used.
– Automated spray sugar coating may be employed.
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– These polymers being acid esters, are insoluble in gastric – Enteric coatings are employed for number of therapeutic, safety and
media that have a pH of up to about 4, they are intended medical reasons.
to hydrate and begin dissolving as the tablets leave – Drugs which causes gastric irritation when directly exposed to gastric
stomach, enter duodenum (pH4-6) and move further mucosa may be EC.
along the small intestine, where the pH increases to a – Drugs which may cause nausea and vomiting when released in to
stomach or destroyed in the stomach may be EC.
range of 7-8.
– When drug has to be released undiluted and in highest concentration
possible within intestine or altering the pharmacokinetics and
– The ionization of the residual carboxyl groups on the bioavailability EC may be an option.
chain and subsequent hydration. The presence of
esterases in the intestinal fluid that break down ester
linkages of polymer chains may also play some role, as
may surface activity effects of bile salts and other
components in bile that enter the upper small intestine via
the bile duct.
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• Sugar and Chocolate Coated Tablets
– CCT are nearly a thing of past and are too easily mistaken
with candies by the children(SCT suffer same
disadvantage).
– It produces glossy, elegant and easy to swallow tablets.
– It allows the separation of incompatible ingredient
between the core and coating, which is widely utilized to
develop the multivitamin and mineral combination tablets.
– The formulation of CCT/SCT is time consuming process
with lots of skill requirement.
– It may almost double the weight of tablet.
– As per latest trends, water soluble polymers are often
incorporated in sugar solution, automated spray coating is
used along with high drying- efficiency side vented coating
pans are used.
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• Film- Coated Tablets – With less preference for organic solvents, aqueous based
– It contains one or two polymers, possibly a surfactant to procedures are gaining attraction.
facilitate spreading along with a organic solvent.
– Hydroxypropyl cellulose, Hydroxypropyl methylcellulose
– Film coating is faster process (1-2 Hrs) in comparison dissolved in water with suitable plasticizer can develop
with SC (1-2 Days). immediate release film coating.
– The colloidal dispersion of ethylcellulose in water also
make it possible to produce slow or controlled release film
coatings without the use of organic solvents.
– A 30% ethylcellulose dispersion is marketed under the
trade name Aquacoat by the FMC Corporation.
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• Advantages of FCT over SCT • Chewable Tablets (CT)
– FCT has better mechanical strength of the coating based – CT are intended to be chewed in the mouth prior to swallowing and
on elasticity and flexibility of the polymer coating. are not intended to be swallowed intact.
– CT can be administered easily by children and elderly who face
– With little increase in tablet weight, thin FC can retain the difficulty to swallow whole tablet.
debossed markings on tablet. – Bitter or foul tasting drugs are not good candidates for CT.
– Avoidance of sugar can benefit diabetic patients. – Antacids may be formulated as CT, as most of the antacid dosage are
– Less likely mistaken as a candy. larger which results in larger tablets to swallow.
– The antacid gives better acid neutralization, if its chewed well prior to
• Disadvantages of FCT against SC swallowing. This activity of antacid is related to its particle size.
– Difficult to produce FCT with the same elegance.
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• Controlled Release Tablets
– Low cost controlled and sustained release tablets are available.
– Sustained release tablets offer following advantages
• Metered particle emptying from the stomach.
• Utilization of a plurality of coating.
• Several release profile for various population of coating, permitting
immediate release fraction followed by sustained release.
– Theo-Dur containing Theophylline from Key Pharmaceuticals, Inc.
– Oros containing Indomethacin from Alza corporation is producing zero
order sustained release with osmotic pressure principle.
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