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Tablets SHUBHRAJIT MANTRY Asst.Prof Kottam Institute of Pharmacy . A.P

Slide 2:

Introduction Advantages and disadvantages of compressed tablets Types of tablets Tablet Ingredients Tablet granulating technique Tablet compression machine Tableting methods Evaluation of Tablet Scope

Slide 3:

Tablet is defined as a solid unit dosage form of medicament or medicaments containing with or without excipients and are prepare by moulding method or by compression method. According to the Indian Pharmacopoeia Pharmaceutical tablets are solid, flat or biconvex dishes, unit dosage form, prepared by compressing a drugs or a mixture of drugs, with or without diluents.

Slide 4:

The advantages of the Tablet dosage form are: 1. They are unit dosage form and offer the greatest capabilities of all oral dosage form for the greatest dose precision and the least content variability. 2. Cost is lowest of all oral dosage form. 3. Lighter and compact. 4. Easiest and cheapest to package and strip. 5. Easy to swallowing with least tendency for hang-up. 6. Sustained release product is possible by enteric coating. 7. Objectionable odour and bitter taste can be masked by coating technique. 8. Suitable for large scale production. 9. Greatest chemical and microbial stability over all oral dosage form. 10. Product identification is easy and rapid requiring no additional steps when employing an embossed and/or monogrammed punch face.

Slide 5:

Disadvantages of Tablet dosage form are: 1. Difficult to swallow in case of children and unconscious patients. 2. Some drugs resist compression into dense compacts, owing to amorphous nature, low density character. 3. Drugs with poor wetting, slow dissolution properties, optimum absorption high in GIT may be difficult to formulate or manufacture as a tablet that will still provide adequate or full drug bioavailability. 4. Bitter testing drugs, drugs with an objectionable odor or drugs that are sensitive to oxygen may require encapsulation or coating. In such cases, capsule may offer the best and lowest cost.

Slide 6:

Different types of Tablets (A) Tablets ingested orally: 1. Compressed tablet, e.g. Paracetamol tablet 2. Multiple compressed tablet 3. Repeat action tablet 4. Delayed release tablet, e.g. Enteric coated Bisacodyl tablet 5. Sugar coated tablet, e.g. Multivitamin tablet 6. Film coated tablet, e.g. Metronidazole tablet 7. Chewable tablet, e.g. Antacid tablet (B) Tablets used in oral cavity: 1. Buccal tablet, e.g. Vitamin-c tablet 2. Sublingual tablet, e.g. Vicks Menthol tablet 3. Troches or lozenges 4. Dental cone

Slide 7:

(c) Tablets administered by other route: 1. Implantation tablet 2. Vaginal tablet, e.g. Clotrimazole tablet (D) Tablets used to prepare solution: 1. Effervescent tablet, e.g. Dispirin tablet (Aspirin) 2. Dispensing tablet, e.g. Enzyme tablet (Digiplex) 3. Hypodermic tablet 4. Tablet triturates e.g. Enzyme tablet (Digiplex)

Slide 8:

Single layer tablet

Slide 9:

Chewable tablets Chewable tablets are to be chewed and thus mechanically disintegrated in the mouth. Advantages of chewable tablets: Provide quick and complete disintegration of the tablet and thus obtain a rapid drug effect - Easy administration, especially for infants and elderly people.

Slide 10:

Effervescent tablets Effervescent tablets are dropped into a glass of water before administration during which CO2 is liberated . Advantages of effervescent tablets: 1- To obtain rapid drug action, for example analgesics and antacids. 2- To facilitate drug intake, for example vitamins

Slide 11:

Sublingual and Buccal tablets They are used for drug release in mouth followed by systemic uptake of the drug. A rapid systemic drug effect can thus be obtained without first-path liver metabolism. Sublingual tablets are placed under the tongue.

Slide 12:

Buccal tablets are placed in the side of the check for absorption through oral mucosa.

Slide 13:

Lozenges They are tablets that dissolve slowly in the mouth and so release the drug dissolved in the saliva. Lozenges used for - Local medications in the mouth or throat, e.g. local anaesthetics, antiseptics and antibiotics. Hard candy lozenges , e.g. Halls®

Slide 14:

In addition to the active or therapeutic ingredient(s), tablets contain a number of inert materials. The latter are known as additives or excipients . They may be classified according to the part they play in the finished tablet. Group-I : Contains those which help to impart satisfactory processing and compression characteristics to the formulation. This includes: diluents, binders, glidants and lubricants . Group-II : Helps to give additional desirable physical characteristics to the finished tablet. This includes: disintegrants, colours, and in the case of chewable tablets, flavors and sweetening agents . Group-III: In the case of controlled-release tablets, polymers or waxes or other solubility-retarding materials. TABLET INGREDIENTS

Slide 15:

In addition to active ingredients, tablet contains a number of inert materials known as additives or excipients. Different excipients are: 1. Diluents 2. Binder and adhesive 3. Disintegrants 4. Lubricants and glidants 5. Colouring agents 6. Flavoring agents 7. Sweetening agents

Slide 16:

1. Diluent: Diluents are fillers used to make required bulk of the tablet when the drug dosage itself is inadequate to produce the bulk. Secondary reason is to provide better tablet properties such as improve cohesion, to permit use of direct compression manufacturing or to promote flow. A diluent should have following properties: 1. They must be non toxic 2. They must be commercially available in acceptable grade 3. There cost must be low 4. They must be physiologically inert 5. They must be physically & chemically stable by themselves & in combination with the drugs. 6. They must be free from all microbial contamination. 7. They do not alter the bioavailability of drug. 8. They must be color compatible.

Slide 17:

Commonly used tablet diluents 1. Lactose-anhydrous and spray dried lactose 2. Directly compressed starch-Sta Rx 1500 3. Hydrolyzed starch-Emdex and Celutab 4. Microcrystalline cellulose-Avicel (PH 101and PH 102) 5. Dibasic calcium phosphate dehydrate 6. Calcium sulphate dihydrate 7. Mannitol 8. Sorbitol 9. Sucrose- Sugartab, DiPac, Nutab 10. Dextrose

Slide 18:

2. Binders and Adhesives: These materials are added either dry or in wet- form to form granules or to form cohesive compacts for directly compressed tablet Example: Acacia, tragacanth- Solution for 10-25% Conc. Cellulose derivatives- Methyl cellulose, Hydroxy propyl methyl cellulose, Hydroxy propyl cellulose Gelatin- 10-20% solution Glucose- 50% solution Polyvinylpyrrolidone (PVP)- 2% conc. Starch paste-10-20% solution Sodium alginate Sorbitol

Slide 19:

Superdisintegrants: Swells up to ten fold within 30 seconds when contact water. Example: Crosscarmellose- cross-linked cellulose, Crosspovidone- cross-linked povidone (polymer), Sodium starch glycolate- cross-linked starch. These cross-linked products swell upto 10n fold with in 30 seconds when in contact with water. A portion of disintegrant is added before granulation and a portion before compression, which serve as glidants or lubricant. Evaluation of carbon dioxide in effervescent tablets is also one way of disintegration 3. Disintegrants: Added to a tablet formulation to facilitate its breaking or disintegration when it contact in water in the GIT. Example: Starch- 5-20% of tablet weight. Starch derivative – Primogel and Explotab (1-8%) Clays- Veegum HV, bentonite 10% level in colored tablet only Cellulose Cellulose derivatives- Ac- Di-Sol (sodium carboxy methyl cellulose) Alginate PVP (Polyvinylpyrrolidone), cross-linked

Slide 20:

4. Lubricant and Glidants: Lubricants are intended to prevent adhesion of the tablet materials to the surface of dies and punches, reduce inter particle friction and may improve the rate of flow of the tablet granulation. Glidants are intended to promote flow of granules or powder material by reducing the friction between the particles. Example: Lubricants- Stearic acid, Stearic acid salt - Stearic acid, Magnesium stearate, Talc, PEG (Polyethylene glycols), Surfactants Glidants- Corn Starch – 5-10% conc., Talc-5% conc., Silica derivative - Colloidal silicas such as Cab-O-Sil, Syloid, Aerosil in 0.25-3% conc. Reducing friction between the particles To improve the flow properties of the granulations To reduce the friction during tablet ejection between the walls of the tablet and the walls of the die cavity

Slide 21:

5. Coloring agent: The use of colors and dyes in a tablet has three purposes: (a) Masking of off color drugs (b) Product Identification (c) Production of more elegant product All colorants used in pharmaceuticals must be approved and certified by the FDA (food & Drug Administration ). Dyes are generally listed as FD&C (food, Drug & Cosmetic Dyes) dyes and D&C (Drug & Cosmetic Dyes). Example: FD & C yellow 6-sunset yellow FD & C yellow 5- Tartrazine FD & C green 3- Fast Green FD & C blue 1- Brilliant Blue FD & C blue 2 - Indigo carmine D & C red 3- Erythrosine. D & C red 22 – Eosin Y

Slide 22:

6. Flavoring agents: For chewable tablet- flavor oil are used 7. Sweetening agents: For chewable tablets: Sugar, mannitol. Saccharine (artificial): 500 time’s sweeter than sucrose Disadvantage: Bitter aftertaste and carcinogenic Aspartame (artificial) Disadvantage: Lack of stability in presence of moisture

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Slide 26:

Absorption of drug form tablets

Slide 39:

TABLETING PROCEDURE Filling Compression Ejection

Slide 40:

TABLET COMPRESSION MACHINES Tablets are made by compressing a formulation containing a drug or drugs with excipients on stamping machine called presses. Tablet presses are designed with following basic components: Hopper : for holding and feeding granulation to be compressed. Dies : that define the size and shape of the tablet. Punches : for compressing the granulation within the dies. Cam tracks : for guiding the movement of the punches. Feeding mechanisms : for moving granulation from the hopper into the dies. Ejector blade : To remove the prepared tablets.

Slide 42:

Upper and Lower Collar Collar locker SINGLE PUNCH MACHINE

Slide 45:

Multi-station rotary presses The head of the tablet machine that holds the upper punches, dies and lower punches in place rotates As the head rotates, the punches are guided up and down by fixed cam tracks, which control the sequence of filling, compression and ejection. The portions of the head that hold the upper and lower punches are called the upper an lower turrets The portion holding the dies is called the die table The pull down cam (C) guides the lower punches to the bottom, allowing the dies to overfill The punches then pass over a weight-control cam (E) , which reduces the fill in the dies to the desired amount

Slide 46:

A swipe off blade (D) at the end of the feed frame removes the excess granulation and directs it around the turret and back into the front of the feed frame The lower punches travel over the lower compression roll (F) while simultaneously the upper punches ride beneath the upper compression roll (G) The upper punches enter a fixed distance into the dies, while the lower punches are raised to squeeze and compact the granulation within the dies After the moment of compression, the upper punches are withdrawn as they follow the upper punch raising cam (H) The lower punches ride up the cam (I) which brings the tablets flush with or slightly above the surface of the dies

Slide 47:

The tablets strike a sweep off blade affixed to the front of the feed frame (A) and slide down a chute into a receptacle At the same time, the lower punches re-enter the pull down cam (C) and the cycle is repeated

Slide 50:

EVALUATION OF TABLET 1. General Appearance: The general appearance of a tablet, its identity and general elegance is essential for consumer acceptance, for control of lot-to-lot uniformity and tablet-to-tablet uniformity. The control of general appearance involves the measurement of size, shape, color, presence or absence of odor, taste etc. 2. Size & Shape: It can be dimensionally described & controlled. The thickness of a tablet is only variables. Tablet thickness can be measured by micrometer or by other device. Tablet thickness should be controlled within a ± 5% variation of standard value. 3. Unique identification marking: These marking utilize some form of embossing, engraving or printing. These markings include company name or symbol, product code, product name etc. 4. Organoleptic properties: Color distribution must be uniform with no mottling. For visual color comparison compare the color of sample against standard color. 5. Hardness and Friability: Tablet requires a certain amount of strength or hardness and resistance to friability to withstand mechanical shakes of handling in manufacture, packaging and shipping. Hardness generally measures the tablet crushing strength

Slide 52:

6.Friability: Friability of a tablet can determine in laboratory by Roche friabilator. This consist of a plastic chamber that revolves at 25 rpm, dropping the tablets through a Distance of six inches in the friabilator, which is then operate for 100 revolutions. The tablets are reweighed. Compress tablet that lose less than 0.5 to 1.0 % of the Tablet weigh are consider acceptable.

Slide 53:

7.Drug Content and Release: (I) Weight Variation test (U.S.P.): T ake 20 tablet and weighed individually. Calculate average weight and compare the individual tablet weight to the average. The tablet pass the U.S.P. test if no more that 2 tablets are outside the percentage limit and if no tablet differs by more than 2 times the percentage limit. (II) Content Uniformity Test: Randomly select 30 tablets. 10 of these assayed individually. The Tablet pass the test if 9 of the 10 tablets must contain not less than 85% and not more than 115% of the labeled drug content and the 10 th tablet may not contain less than 75% and more than 125% of the labeled content. If these conditions are not met, remaining 20 tablet assayed individually and none may fall out side of the 85 to 115% range . (III) Disintegration Test (U.S.P.): The U.S.P. device to test disintegration uses 6 glass tubes that are 3” long; open at the top and 10 mesh screen at the bottom end. To test for disintegration time, one tablet is placed in each tube and the basket rack is positioned in a 1-L beaker of water, simulated gastric fluid or simulated intestinal fluid at 37 ± 2 0 C such that the tablet remain 2.5 cm below the surface of liquid on their upward movement and not closer than 2.5 cm from the bottom of the beaker in their downward movement. Move the basket containing the tablets up and down through a distance of 5-6 cm at a frequency of 28 to 32 cycles per minute. Floating of the tablets can be prevented by placing perforated plastic discs on each tablet. According to the test the tablet must disintegrate and all particles must pass through the 10 mesh screen in the time specified. If any residue remains, it must have a soft mass. Disintegration time: Uncoated tablet: 5-30 minutes Coated tablet: 1-2 hours

Slide 55:

8. Dissolution Test (U.S.P.): Two set of apparatus: Apparatus-1: A single tablet is placed in a small wire mesh basket attached to the bottom of the shaft connected to a variable speed motor. The basket is immersed in a dissolution medium (as specified in monograph) contained in a 100 ml flask. The flask is cylindrical with a hemispherical bottom. The flask is maintained at 37±0.5 0 C by a constant temperature bath. The motor is adjusted to turn at the specified speed and sample of the fluid are withdrawn at intervals to determine the amount of drug in solutions. Apparatus-2: It is same as apparatus-1, except the basket is replaced by a paddle. The dosage form is allowed to sink to the bottom of the flask before stirring. For dissolution test U.S.P. specifies the dissolution test medium and volume, type of apparatus to be used, rpm of the shaft, time limit of the test and assay procedure for. The test tolerance is expressed as a % of the labeled amount of drug dissolved in the time limit.

Slide 59:

TABLET COATING Tablet coatings perform one or more of the following functions. They may: mask the taste of unpalatable drugs, protect the drug from deterioration due to light, oxygen or moisture, separate incompatible ingredients, control the release of medicament in the gastrointestinal tract, and provide an elegant or distinctive finish to the tablet. The materials used for coating may largely comprise sucrose (sugar coating), water-soluble film-forming polymers (film coating) or substances which are soluble in the intestinal secretions but not in those of the stomach (enteric coating). These types of coating can all be applied by the pan or fluid-bed processes; the compression coating technique is suitable for sugar and enteric coatings, but not for film coating.

Slide 62:

Standard Coating Pan Immersion-tube system Glatt Immersion sword system Pellegrini pan system STANDARD COATING PAN

Slide 63:

PERFORATED PANS Accela cota system Hi-coater system

Slide 64:

PERFORATED PANS (continue…) Dria coater pan Glatt coater

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Slide 66:

Types of coating processes Three main types are used in the pharmaceutical industry today; - Film coating - Sugar coating - Compression coating

Slide 67:

1- Film coating (the most popular today) It involves the deposition, usually by spraying method, of a thin uniform film of a polymer formulation surrounding a tablet. Materials polymers solvents plasticizers colorants

Slide 68:

TYPES OF FILM COATING Immediate release Modified release

Slide 69:

PLASTICIZERS Internal plasticizers : Chemical modification of the polymer that alters the physical properties. Degree of substitution Type of substitution Chain length. External plasticizers : They are non-volatile or the other polymer, which when include with primary polymeric film former, changes the Flexibility Tensile strength, or Adhesion properties of the resulting film.

Slide 70:

Concentration Of Plasticizer Expressed As - The amount of polymer being plasticized. Recommended Level of Plasticizer : 1 to 50% by weight of the film former. EXAMPLES Castor oil; propylene glycol of 200 and 400 series; and surfactants eg; Tweens; Spans; and organic acid esters. Water- soluble plasticizer : PEG, propylene glycol. Organic- soluble plasticizer : castor-oil and Spans.

Slide 71:

COLORANTS Colorants may be soluble in the solvent system or suspended as insoluble powders. Used to provide distinctive color and elegance to a dosage form. To achieve proper distribution of suspended colorants in the coating solutions requires the use of fine-powdered colorants (< 10 microns ). Most of colorants are synthetic DYES or LAKES OF DYES approved by the FD&C and D&C.

Slide 72:

LAKES : derived from dyes by precipitating with carriers. Eg ; alumina or talc. Lakes contains 10 to 30 % of the pure dye content. For very light shade, concentration : less than 0.01 %. For dark shade, concentration : more than 2.0 % Examples Inorganic materials: iron oxides Natural coloring materials :Anthocyanins, caramel, carotenoids, chlorophyll, indigo, flavones, turmeric, and carminic acid. Various concentrates promoted as achieving less lot-to-lot color variation Opalux – Opaquant color concentrate for sugar coating. Opaspray- Opaque color concentrate for film coating. Opadry – Complete film coating concentrate

Slide 73:

Enteric Coating

Examples of enteric coated OTC products :

Examples of enteric coated OTC products Enteric coated aspirin E.g. Micropirin ® 75mg EC tablets Enteric coated peppermint oil E.g. Colpermin ®

Slide 76:

- Typically, tablets are sugar coated by panning technique, using traditional rotating sugar-coating pan with a supply of drying air (thermostatically controlled). - The pan is automatically rotated, allowing tablets to tumble over each other while making contact with the coating solutions which are gently poured or sprayed, portion wise onto the tablets with warm air blown to hasten drying. Each coat is applied only after the previous coat is dried.

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Slide 79:

SUGAR COATING Seal coating Sub coating Syrup coating Color coating Polishing printing

Slide 80:

1- Sealing (Waterproofing) This involved the application of one or more coats of a waterproofing substance in the form of alcoholic spray, such as pharmaceutical Shellac (traditionally) or synthetic polymers, such as CAP. ( Unless a modified-release feature needs to be introduced, the amount of the sealing coat applied should be carefully calculated so that there is no negative effect on the drug release characteristics in case of immediate release product.) (WHY Sealing?) a- Sugar-coatings are aqueous formulations which allow water to penetrate directly into the tablet core and thus potentially affecting product stability and possibly causing premature tablet disintegration. b- Application of many coats of partially or completely water-insoluble polymers in this step, enables sugar-coated product to exhibit modified-release pattern (extendedrelease or delayed "enteric"- release characteristics).

Slide 81:

2. Subcoating - Large quantities of sugar-coatings are usually applied to the tablet core (typically increasing the tablet weight by( 50- 100%) WHY? In order to round off the tablet edge. Much of this material build-up occurs during this stage and is achieved by adding a bulking agent such as Calcium carbonate, to the sucrose solution. - Antiadherents e.g. Talc may be added after partial drying to prevent sticking of the tablets together.

Slide 82:

3- Smoothing The subcoating stage results in tablets with rough surfaces. To facilitate the color application (which requires smooth surface), subcoated tablets are smoothed out by a thick sucrose syrup coating. 4 - Coloring Color coatings usually consist of thin sucrose syrup containing the requisite coloring materials. (water-soluble dyes or water-insoluble pigments may be used) This step must be done into a clean pan deprived of any residues from the previous operations.

Slide 83:

5- Polishing After the coloring step, the tablet surfaces tend to be smooth but somewhat dull in appearance. To achieve glossy finish, final stage involving application of waxes (beeswax carnuba wax) is employed. 6- Printing Different tablets could be identified by manufacturer' logo,product name, dosage strength or other appropriate code.For sugar-coated tablets, such identification could be only achieved by printing process using special edible inks.

Example of sugar coated tablets :

Example of sugar coated tablets Brufen® POM Available in 200mg and 400mg strength Premarin® POM Conjugated oestrogens 625mcg (maroon) and 1.25mcg (yellow) Colofac ® P Mebeverine hydrochloride 100mg Round, white, sugar coated Kalms ® GSL 45mg Hops powder,90mg Gentian powdered extract, and 135mg Valerian powdered extract

Summary of Polymers used in pharmaceutical formulations as coating materials.:

Summary of Polymers used in pharmaceutical formulations as coating materials. Polymer Trade name Application Shellac EmCoat 120 N Marcoat 125 Enteric Coatings Taste/Odor Masking Cellulose acetate Aquacoat CPD® Sepifilm ™ LP Klucel ® Aquacoat ® ECD Metolose ® Enteric Coatings Taste masking Sustained release coating Sub coat moisture and barrier sealant pellet coating Polyvinylacetate phthalate Sureteric ® Enteric Coatings Methacrylate Eudragit® Enteric Coatings Sustained Release Coatings Taste Masking Moisture protection Rapidly disintegrating Films

Slide 87:

3- Compression Compression-coating of tablets Although less popular, it gained increased interest in recent years for creating modified-released products involves the compaction of granular materials around preformed tablet core using specially designed tableting equipment. Compression coating is a dry process.

Slide 90:


Coating Problems:

Coating Problems picking/chipping roughness sticking film cracking/peeling

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Slide 93:

TABLETTING DEFECTS An ideal tablet should be free from any visual defect or functional defect which is often difficult to achieve mainly because of the complexities of tablet presses; and/or the greater demands of quality. Visual defects are due to inadequate fines or inadequate moisture in the granules ready for compression or due to faulty machine setting whereas Functional defects are due to faulty formulation. However, these defects may be attributed to the following factors: Tableting Process Excipient Machine

Slide 94:

The defects related to Tableting Process are as follows: i) CAPPING: due air-entrapment in the granular material. ii) LAMINATION: due air-entrapment in the granular material. iii) CRACKING: due to rapid expansion of tablets when deep concave punches are used. The defects related to Excipientare as follows: iv) CHIPPING: due to very dry granules v) STICKING ] vi) PICKING ] ------ due to more amount of binder in the wet granules vii) BINDING ]

Slide 95:

The defect related to Machine: Ix) DOUBLE IMPRESSION: due to free rotation of the punches, which have some engraving on the punch faces The defect related to more than one factor: viii) MOTTLING: due to any one or more of these factors: Due to a colored drug, which has different color than the rest of the granular material? (Excipients-related); improper mixing of granular material (Process-related); dirt in the granular material or on punch faces; oil spots by using oily lubricant.

Slide 96:

CAPPING ‘ Capping ’ is the term used, when the upper or lower segment of the tablet separates horizontally, either partially or completely from the main body of a tablet and comes off as a cap, during ejection from the tablet press, or during subsequent handling. Reason : Capping is usually due to the air–entrapment in a compact during compression, and subsequent expansion of tablet on ejection of a tablet from a die.

Slide 99:

LAMINATION / LAMINATING Definition: Lamination’ is the separation of a tablet into two or more distinct horizontal layers. Reason: Air–entrapment during compression and subsequent release on ejection. The condition is exaggerated by higher speed of turret.

Slide 101:

CHIPPING Definition: ‘Chipping’ is defined as the breaking of tablet edges, while the tablet leaves the press or during subsequent handling and coating operations. Reason: Incorrect machine settings, specially mis-set ejection take-off.

Slide 103:

CRACKING Definition: 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 : It is observed as a result of rapid expansion of tablets, especially when deep concave punches are used .

Slide 105:

STICKING / FILMING Definition: ‘ Sticking’ refers to the tablet material adhering to the die wall. ‘Filming’ is a slow form of sticking and is largely due to excess moisture in the granulation. Reason : Improperly dried or improperly lubricated granules.

Slide 107:

PICKING Definition: Picking’ is the term used when a small amount of material from a tablet is sticking to and being removed off from the tablet-surface by a punch face. The problem is more prevalent on the upper punch faces than on the lower ones. The problem worsens, if tablets are repeatedly manufactured in this station of tooling because of the more and more material getting added to the already stuck material on the punch face. Reason: Picking is of particular concern when punch tips have engraving or embossing letters, as well as the granular material is improperly dried.

Slide 110:

BINDING Definition: ‘Binding’ in the die, is the term used when the tablets adhere, seize or tear in the die. A film is formed in the die and ejection of tablet is hindered. With excessive binding, the tablet sides are cracked and it may crumble apart. Reason: Binding is usually due to excessive amount of moisture in granules, lack of lubrication and/or use of worn dies.

Slide 113:

MOTTLING Definition: ‘Mottling’ is the term used to describe an unequal distribution of colorant a tablet, with light or dark spots standing out in an otherwise uniform surface. Reason: One cause of mottling may be a coloured drug, whose colour differs from the colour of excipients used for granulation of a tablet.

Slide 115:

DOUBLE IMPRESSION Definition: ‘Double Impression’ involves only those punches, which have a monogram or other engraving on them. Reason: At the moment of compression, the tablet receives the imprint of the punch. Now, on some machines, the lower punch freely drops and travels uncontrolled for a short distance before riding up the ejection cam to push the tablet out of the die, now during this free travel, the punch rotates and at this point, the punch may make a new impression on the bottom of the tablet, resulting in ‘Double Impression’. If the upper punch is uncontrolled, it can rotate during the short travel to the final compression stage and create a double impression.

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