Keywords: film layered tablets, effervescent tablets, enteric coated tablets
Tablets are sound dosage varieties usually containing active pharmaceutical element and excipients in natural powder, crystalline or granular form with or without diluents which is prepared either by moulding or compression process. They are simply sound, biconvex or toned in form and vary in size, condition and weight which is depends on the medicaments which are being used for preparation. Also, they are differing in hardness, disintegration; dissolution characteristics and width rely upon their expected use and method of manufacture. Tablets are the hottest solid dosage varieties because of their advantages and attractiveness increasing daily. Tablet usually is made up of filler, diluents, binders, lubricants, glidants, disintegrants, antiadherent, colouring agents and flavouring providers as excipients. [Ansel's Pharmaceutical Medication dosage Forms and Medicine Delivery Systems, Eighth Edition, Loyd V. Allen, Jr, Nicholos G. Popovich, Howard C. Ansel, 2005, pp-228-245]
Unit dosage varieties with accurate, secure medication dosage and great detail and a minimum of variability.
Most stable with respect to physical, chemical substance and microbiological characteristics.
Cheapest oral medication dosage form, easy to handle, use and perform with attractive and graceful appearance.
Cheap, easy to swallow and development does not require and additional control steps.
Provide cover of medicaments from atmospheric conditions like air, dampness and light, etc.
Provide prolonged stability to medicaments.
Low processing cost as compare to other sturdy dosage varieties and large level production can be done.
Administration of tiny dose of medication in accurate amount.
Unpleasant style can be masked by sweets coating.
Easy to separate into halves and quarters whenever small fraction dose is necessary.
Formulate as a particular release products such as enteric or delayed release products.
Packing and development is cheap and will not require more space for storage.
Drugs that are amorphous and low denseness identity are difficult to compress into tablet.
Hygroscopic drugs are not ideal for compressed tablets.
Drugs with low or poor drinking water solubility, sloe dissolution, high absorbance in GI tract may be difficult to formulate.
Sensitive to air drugs may necessitate special finish.
Cost of production may be increase because of covering and encapsulation to eliminate bitter and annoying taste.
Some tablet may cause problem in bioavailability.
Difficult to formulate liquid in tablet and swallowing is difficult specifically for children and unwell patients.
There are various kinds of tablets in line with the intended useful and manufacturing process.
Compressed tablets: Tablets can be made by compression of 1 or more dynamic pharmaceutical element with excipients by basic ways of tablet manufacturing. These kinds of tablets usually intended to provide raid medicine release and disintegration. Tablets are covered after compression.
Multiple compressed tablets: Multiple compressed tablets are ready by compressing the material more than once. These are known as multiple layered tablets or tablet within tablet. Layered are will depend on range of fills. Layered tablets are prepared by compaction of fill up material in pass away accompanied by additional of fill material and compression.
Delayed action or Enteric covered tablets: These kinds of tablets include a coating which avoid dissolution of tablets in Gastro Intestinal Trail (GIT) and disintegrate in intestinal fluids thus rendering delayed release features. Enteric coating is generally apply when drug substance is unstable in gastric substance and may demolished or could cause discomfort in gastric mucosa or even to extent absorption of drug from intestine. Normally finish materials blended with acid and acid operation or altered natural polymers. Most commonly used finish polymers are: Cellulose acetate phthalate (CAP), polyvinyl acetate phthalate (PVAP) and hydroxyl propyl methyl cellulose phthalate.
Sugar covered tablet: Compressed tablets may be coated with coloured or uncoloured sweets layer and the coater is normal water soluble and dissolve quickly after swallowing. Sugar coat protects drug from environment, remove bitter taste and odour, enhance the appearance of tablet and permit identifying information. Sugars covering has some disadvantages like increase layer of development, require knowledge for coating, increase size and weight.
Film coated tablets: Tablets are compressed with a slim covering of polymer which forms a pores and skin like film over tablet. The film is usually coloured, stronger and less huge. The coating is designed to rupture and expose of tablet at desired location within GIT. Mostly used polymers are Hydroxy propyl cellulose, Hydroxy ethyl and propyl methyl cellulose.
Chewable tablet: These kinds of tablets have smooth surface, creamy bottom and usually flavoured and coloured mannitol, rapid disintegration which allow dissolving quickly in mouth. These types usually useful for administration of large dose to children and men and women.
Buccal tablets and sublingual tablets: Buccal and sublingual tablets are flat in form and intended to dissolve medication in buccal cavity or under the tongue for mucosa absorption. These techniques useful for drugs that are damaged by gastric fluid or poor absorption in GIT. Buccal tablets erode slowly but surely and sublingual tablets dissolve quickly and produce immediate effect.
Troches and Lozenges: These are intended to slowly dissolution typically for local impact but sometimes for systemic absorption. Troches and Lozenges are disc designed which contain active component and flavouring agent in hard candy or sugar platform.
Dental cones: oral cones are designed to put in place the empty outlet for avoidance of bacterial growth and sometime bleeding by formulated with coagulant. Teeth cones release gradually for long length of time.
Vaginal tablet: Genital tablets are ready by compression and designed to match snugly on clear plastic inserter devices in uncoated bullet molded or ovoid tablets that happen to be put into vagina for local effects with gradual dissolution. They contain anti bacterial effect and also known as vaginal inserts.
Implantation tablet: Implantation tablets are injected under your skin by giving a small surgical cut in to the skin. A special injector a hallow needle and plunger may necessitate for administration. Reason for these tablets is to extend drug impact from month to yr. These tablets are implanted intramuscularly or subcutaneous so they need to be sterile and stuffed in sterile pot. [Pharmaceutics - I, P. V. KASTURE, S. R. PARAKH, S. A. HASAN, S. B. GOKHALE, June 2008, pp-14-7, 21]
Effervescent tablet: Effervescent tablets prepared by compression of granular salts which release in contact with water.
Dispensing tablets: These kinds of tablets are no more use because that they had dangerous potential. They could be termed compounding tablets since it contain highly strong drug and pharmacist utilize it for ingredient prescription.
Hypodermic tablets: Hypodermic tablets are very soft moulded tablets that have soluble ingredient and used for extemporaneous parenteral prep by physician. They are no longer utilized since it is difficult to achieve sterility and option of stable water.
Tablet triturates: tablet triturates are almost never use now a days because they're obsolete. They can be small, cylindrical, molded which contain small amount of potent drug. They need to be commonly soluble in normal water and minimum amount amount pressure require during make. Triturates placed into pills or dissolved in water to provide exact potent medication.
Excipients are substance other that active component in formulation of tablet. The roles of excipients are to ensure tabletting procedure satisfactory and ensure that tablets of specified quality are ready. Depend on planned use; they are simply subcategorised in several groupings. However excipients have an impact on properties of tablets.
A little bit of powder requires developing ideal size tablet for easy handling. Normally tablet consider 50mg so some amount of bulk medicine requires to incorporation in formulation of tablet which enhance size of tablet. These powders known as diluents or fillers. The perfect dilute must have pursuing properties- cheap, chemically inert, satisfactory preference, good compactability and dilution capacity, biocompatible, good biopharmaceutical properties and non hygroscopic.
A single substance cannot fulfil each one of these requirements so different compound have gained use as diluents mainly carbohydrates and inorganic salts sometimes. The most frequent diluent is lactose because it own a sires of good properties like dissolves readily in drinking water, has a pleasurable flavour, non hygroscopic is rather non reactive and shows good compact capacity. Its main limitation is that many people have intolerance to lactose. Basically lactose is accessible in two forms crystalline and amorphous. Other glucose and sweets alcohols such as glucose, sucrose, and mannitol have been used as alternative fillers, usually in chewable tablets or lozenges for their pleasant tastes. Other important example of the filler can be an inorganic element, dicalcium phosphate dehydrate. It is insoluble in drinking water and also non hygroscopic but have hydrophilic property i. e. easily wetted by water. It also has good stream ability and for that reason it is employed mostly in immediate compaction. [Michael, Pharmaceutics: the design and manufacture of drugs. - 3rd ed. - Edinburgh : Churchill Livingstone, 2007. ] [ Leon Lachman, Herbert A. Lieberman and Joseph L. Kanig. (1991). the idea and practise of industrial pharmacy. 3rd addition: Varghese posting house. Web page no. 293- 303. ]
According to Michael, 2007, a disintegrant is added in formulation of tablet, which promotes drug dissolution and provide an effective surface, when comes in contact to liquid and reduces in small fragments. The process of disintegration for tablet occurs in main two steps
 Tablet wets by sold and pores it
 Reduces of tablet into small fragments such as aggregation of primary contaminants into small medication particles. Disintegrant advised in some mechanism such as bloating of debris, wetting effect, repulsion of particle and particle recovery.
Most common types of disintegrants in tablets are maize, potato and corn starch. the attention of starch is up to 10% required but today normally improved starch or revised cellulose are used which are very high bloating disintegrants. So it's requires typically 1-5% by weight which aid particle-particle repulsion.
However, disintegrants can be blended with other elements such as granules to increase effective disintegration of the tablet into smaller fragments.
Leon Lachman et al, 1991, suggested that other band of disintegrants may function by producing gas, normally skin tightening and, in touch with normal water. This types of disintegrants used in effervescent tablets and normally not in tablets that should be swallowed as a solid. The liberation of skin tightening and is attained by the decomposition of carbonate salts or bicarbonate in touch with acidic water. The acidic pH is obtained by adding citric acid and tartaric acid. [ Michael, Pharmaceutics: the design and make of medications. - 3rd ed. - Edinburgh : Churchill Livingstone, 2007. 3. Leon Lachman, Herbert A. Lieberman and Joseph L. Kanig. (1991). the idea and practise of industrial pharmacy. 3rd addition: Varghese posting house. Page no. 293- 303]
Binder is put into the tablet or filler mixture to ensure that tablets and granules have sufficient mechanised strength. There are many ways to add it in powder-
Mixed with powder before moist granulation which completely or partially dissolves during agglomeration process by agglomeration water.
Mixed with other element as a dried out powder solution before compaction process
As a remedy used as agglomeration liquid during damp granulation.
Typically 2-10% of binders or dry binders are being used in formulation. Most traditions common binders are starch, sucrose and gelatine but now most frequent are polyvinylpyrrolidone and cellulose derivatives which have improved adhesive properties. Types of dry out binders are microcrystalline cellulose and crosslinked polyvinylpyrrolidone. Solution binders are most reliable therefore it is integrated in granules.
The role of the Glidant is to improve the flow potential of the powder. Glidants are used in formulation for immediate compaction nonetheless they are also used in granulation process before tabletting which ensure flow ability of tablet mass for broadband production. Customarily talc has been used as glidant about 1-2% attention in formulation but nowadays the most commonly used glidant is colloidal silica added in suprisingly low percentage about 0. 2% by weight. [ Michael, Pharmaceutics: the look and produce of drugs. - 3rd ed. - Edinburgh : Churchill Livingstone, 2007. 3. Leon Lachman, Herbert A. Lieberman and Joseph L. Kanig. (1991). the idea and practise of professional pharmacy. 3rd addition: Varghese posting house. Web page no. 293- 303]
The function of lubrication is to ensure low lubrication between stable and the pass away wall structure during tablet creation and ejection. High friction during tabletting can result in a series of problems such as inadequate tablet quality and may even stop development. Lubrication is most important including in almost all of production.
Lubrication can manage mainly two mechanism, fluid lubrication and boundary lubrication. In fluid lubrication, water is achieved between die surface and tablet surface which separates the moving surfaces of the solids from each other and reduces the friction. While in boundary lubrication, it is considered as a surface sensation, as here moving surface is segregated by a very thin layer of lubricants. Such boundary lubricants are Stearic acid salts, mainly Magnesium Stearate which is most generally use due to its superior lubrication properties. Besides minimizing friction, lubricants may also causes undesired changes such as minimizing tablet strength with bonding between the particles during compaction. Because of hydrophobic properties of lubricants, tablet disintegration and dissolution are often retarded by the addition of lubricants. Thus, least amount of lubricants are utilized, i. e. concentrations of 1% or below, often 0. 25-0. 5%. to avoid these unwanted effects, more hydrophilic substances have been recommended as alternatives to the hydrophobic lubricants. For example, surface active real estate agents and polyethylene glycols and sometimes a combination of hydrophilic and hydrophobic substances might also be utilized. [M. E Aulton, Pharmaceutics, The Technology of Dosage Form Design, Second Model, 2002, pp. 408-412]
Antiadherent are substance which reduce adhesion between powder and punch faces which prevent sticking of contaminants to punches. The sticking is principally influenced by moisture content of the powder. Such adherence especially prone to happen if the tablet punches have marking or icons which lead to a build of slender layer of natural powder on the punches which will lead to a unequal and matt tablet surface with unclear markings or icons. Some lubricants such as Magnesium Stearate also have antiadherent properties. However, other substances with limited capability to reduce friction can also act as antiadherent such as talc and starch. [M. E Aulton, Pharmaceutics, The Science of Dosage Form Design, Second Release, 2002, pp. 408-412]
Sorbents are substances which has capacity to sorbing some quantities of fluid into dried state. So oil and oil-drug alternatives can be designed into combination of powder and compacted into tablets. Most commonly used sorbents are Microcrystalline Cellulose and Silica. [M. E Aulton, Pharmaceutics, The Technology of Dose Form Design, Second Release, 2002, pp. 408-412]
Flavouring providers are included into a formulation to remove unpleasant tastes of bitter medication or even to make tablet more pleasant or mask. This is achieved by covering or by adding some drug debris. Most of Flavouring real estate agents are thermolabile so it cannot be added in process which entail heating. They are simply blended with granules as alcoholic solution.
The try to add colourant is to assist identification of tablet, improve looks of tablet and patient conformity. Mostly, colourant are added during finish of tablet but some of colourant may be added in formulation prior to compaction. Colourant may be added as an insoluble powder or dissolved in granulation water and the second option technique may produce color deviation by migration of soluble dye during drying level.
Three types method of tablet preparation-
 Direct compression method
 Moist granulation
 Dry granulation
Some chemicals have free streaming and cohesive properties so they are really enable to compress directly in a tablet machine without granulation of computer. Some chemicals lacking of these features so some excipients like filler, disintegrants agencies, lubricants and glidants are being used to impart these features for production of tablets by immediate compression.
Figure (A) Steps of immediate compression tableting
Some precaution must be taken during immediate compression to avoid air entrapment which cause capping, splitting, or laminating of tablets. Pressured feeders or induced feeders are used to reduce air entrapment, make filling up powder more thick and amenable to compaction.
Capping also may be brought on by punches that aren't perfectly clean and flawlessly even or by too much fines granulation. Some aged or improperly stored tablets also may display splitting and other physical deformations.
Granulation is process where primary powder allergens are made to form large and these kind of multi particle called granules. In pharmaceutical industry, granules are of help in creation of tablets and capsules in runs of particle size between0. 2 to 0. 5mm.
Granulation helps prevent segregation of constituents of natural powder, improve flow ability of natural powder, improve compaction characteristics of combination and reduce dangerous dust.
Wet granulation is widely used method for development of compressed tablets such as flowing steps-
In this task, specified levels of active ingredient, diluents or fillers, and disintegrating agents are combined by mechanical natural powder blender or mix until uniform.
Most trusted fillers are lactose, microcrystalline cellulose, starch, powdered sucrose, and calcium mineral phosphate. Choices of filler be based upon the knowledge of make, cost and compatibility with formulation. On the list of fillers, lactose is most preferred due to its solubility and compatibility, and microcrystalline cellulose, due to its easy compaction compatibility and consistent uniformity of source.
Disintegrating agencies include croscarmellose, corn and potato starches, sodium starch glycolate, sodium carboxymethylcellulose, polyvinyl polypyrrolidone (PVP), cation exchange resins, alginic acid and other materials which swell or increase on exposure to moisture and really helps to breakup tablets in gastrointestinal track (GIT). Mainly croscarmellose and sodium starch glycolate are being used for their high drinking water uptake and quick action. Mainly up to 5-10% of starch is suited to formulation, but up to about 20% may be used to facilitate more rapid tablet disintegration. The quantity of disintegrant is not necessarily used but sometime it added in planning of granulation and sometime half of it added to tablet development which called double disintegration of tablet. One portion of disintegrant assist break up of tablet into bits and other portion breakup portions into particles.
A liquid binder is currently put into the powder to facilitate adhesion of powder particles. A damp mass resembling dough is developed and used to get ready the granulation. A good binder is very important for hardness of tablet and will not hinder the discharge of medication from the tablet.
Most trusted binders are povidone, an aqueous prep of corn starch (10-20%), methyl cellulose (3%), carboxymethylcellulose, and microcrystalline cellulose. Some drugs may be adversely afflicted by an aqueous binder then non-aqueous alternatives or dried up binder can be utilized. The amount of binders is an integral part of operation which retains integrity of tablet after compression. However, attention must be exercised not to over or underwet natural powder often underwet can effect too hard granules for proper tablet formulation and overwet can end result too smooth and tend to crumble in under wetting. After getting desired dump mass a colorant or flavorant may be added to prepare a granulation with an added features.
The Dump Mass is pressed through 6 or 8 mesh size to prepare granules. This technique may be done by hand or by special equipment which prepares granules by extrusion process. The final product are distributed on large little bit of paper in trays and dried out.
Granules may be dried in special drying cupboards which is thermostatically manipulated at constantly record the time, temperature and dampness. Fluid bed drier and holder drier are commonly used for during process.
After drying, the granules are exceeded through a display of a smaller clutter than that used to prepare the original granulation. How big is granules depends upon how big is the punches to be utilized. Usually 12 to 20 mesh sizes are used for granulation. Sizing of the granules is essential so that the die cavities for tablet compression may be completely or quickly crammed by the free streaming granules. Voids or air places left by too large a granulation cause production of unequal tablets.
After dry screening process, a dry out lubricant is propagate over the granulation through an excellent mess display screen which contributes to prep of compressed tablets. Being among the most commonly used lubricants are talc, magnesium stearate, calcium stearate, stearic acid, and sodium stearyl fumarate in runs of 0. 1% to 5%. Lubricants improve movement property of granules form hooper ti pass away, prevent adhesion during compaction, reduce friction between pass away and punch and offer a sheen final product.
Figure (B) Tablet compression by moist granulation [Pharmaceutics - I, P. V. KASTURE, S. R. PARAKH, S. A. HASAN, S. B. GOKHALE, June 2008, pp-14-7, 21]
High shear mixture granulation
Fluid foundation granulation
In this method, powder mixer is compressed in large pieces and subsequently broken down or sized into granules. In this method, either active ingredient or diluent must have cohesive properties. This technique is basically applied to materials which can't be prepared by wet granulation because of moisture degradation properties or thermo-mobile properties of granules. It really is carried out by two steps:
After weighing and the mixing up of elements, the powder mixture is slugged or compressed into large toned tablets about one in. in diameter. Slugs are than split up side or mill and transferred through a display of desired chaos for sizing and sometimes lubricant are added and made by compression.
Instead of slugging, natural powder compactors enable you to increase the thickness of a natural powder by pressing it between rollers at 1 lot to 6 tons of pressure. The small material is split up, measured, and lubricated, and tablets are prepared by compression. Widely used binding providers are methyl cellulose or hydroxylmethyl cellulose (6-12%) which produces good hardness and friability of tablet.
Figure (C) Tablet compression by Dry Granulation [Pharmaceutics - I, P. V. KASTURE, S. R. PARAKH, S. A. HASAN, S. B. GOKHALE, June 2008, pp-14-7, 21]
There will vary types of tabletting machines which are being used in the productivity but similar in basic function and procedure. Each of them compress tablet formulation within metal expire cavity by the pressure exerted by the movement of two material punches, lower punch and an higher punch.
Capping means incomplete and complete parting of the very best or bottom crowns of your tablet from main body of an tablet. While lamination is term used to describe the parting of both or more distinctive levels. Some reasons which are in charge of these problems are the following:
Air is entrapped among the particles through the compression process and does not escape until compression pressure is released.
Die wall membrane pressure triggers enough inner stress to cause a crack which is due to clear plastic deformation of the particles during compaction.
Sometimes credited to deep concave or bevelled border punches.
Development of 'wear band'. This problem can reduced or eradicated by slowing tabletting rate, granules with sufficient moisture, pre-compression, using smooth punches, correct modification punches. [Porter, S C, 1981, Tablet finish, Drug Plastic Indu, May 46, June 44, Aug 40, Sept 50]
This is very important in process control measurement. If anything that can transform the expire filling process can transform tablet weight, it triggers weight deviation because the weight of the tablet being compressed depends upon the amount of the granulation in the die prior to compression. Some causes of deviation are large granules, poor combining of granules with lubricants and glidants, poor granulation move from hopper, dual impression and punch deviation.
Picking is the term used to spell it out the surface materials from tablet that is sticking with being removed from the tablet's surface by way of a punch. It concerns when punching tips have engraving or embossing
Sticking is usually described adhesion of tablet materials to die wall. Because of that, lower punch cannot move widely and additional push must conquer friction between pass away wall and the tablet. These problems can be fixed by design large lettering, adding polishing agent such as colloidal silica or additional lubricants. Some low melting point substances such as polyethylene glycol could also cause sticking at the heat of compression. Such Remedies are addition of high melting point materials and therefore increasing size of tablet.
Mottling is term used unequal syndication of colour on a tablet with light and dark areas. It's due to colour difference of medicine with excipients or drugs whose degradation product is colored. Such problems might be resolved by using colorants but it can cause mottling at the top of surface when granulation goes through drying. To overcome problems, it require to change solvent system, binder system and by reducing temperature.
Tablet layer is program of layer of material to the surface of tablet with some intentional benefits. It is also intended for improved release applications.
Main three types of covering are-
Coating of tablets are for pursuing purposes-
 Safeguard from environment, light and moisture
 To eliminate bitter tastes of some tablets and for easy swallowing of tablets
 Colour layer mask differences in appearance which effect on patient compliance
 Rapid recognition by maker, pharmacist and patient
 Functional films can enable sustained and enteric protection
 Improve looks (elegance), masks and minor difference in natural material appereance
 Enhance strength, reduce dust and mix contamination
This is newer and widely used for tablet coating. Most of newly launched layered products are film coated rather than sugars coating.
Film coating involves covering of tablet by slender film covering of coating water (polymer). Coating water is sprayed in a rotating tablet foundation or foundation fluidised tablet which contains plasticizer, polymer, colourant and solvent. The drying condition permits removal of solvent and leaves a slim level around each tablet. Sometimes aqueous solution or organic solutions are used to reduce eradication of volatile organic and natural compound, health insurance and safety and cost lowering purposes. Film covering polymer should have following properties-
 Maximum solubility to help in dissolution of last product. High soluble for immediate release and low soluble for controlled release.
 Perfect viscosity allowing and hassle free spraying of solution.
 Maximum permeability to maximize shelf life of tablet planning plus some tuned to provide an effective barrier air and water vapour.
 Good mechanical strength to hold up against the impact and abrasion experienced in normal handling which avoids cracks and defects.
Cellulose derivatives like Hydroxypropylmethylcellulosa (HPMC), methylcellulose, hydroxypropylcellulose (HPC) and Methacrylate amino ester copolymer are available polymer for film layer.
Sugar coating will involve the successive program of sucrose based solutions to tablet cores in suited equipment. Some levels in development of sugar layered tablets are-
 Sealing of tablet core- provide normal water proofing key from covering process and shellac, cellulose acetate phthalate are usually used in closing process.
 Sub coating- it is the actual start of sugars coating which provides necessary build-up to roundup the tablet edge. Bulking agents such as calcium mineral carbonate or talc added in sucrose solution with gum.
 Smoothing - it increases tablet size to predetermined dimension by syrup solution. This solution is made up of pigments, starch, gelatine, acacia or opacifier.
 Colouring- dyes or pigments
 Polishing- tablets have to be polished to achieve final style by waxes like beeswax, carnubawax or hard paraffin.
Press coating consists of compaction of granules materials around primary of tablet with the use of compressing equipment like Manesty Drycota. Today press finish is used directly into separate incompatible put core and layer layer. This process requires some health care and large or irregularly size agglomerate of granules could cause central to tilt in pass away. Down sides of process arise from complexities of device found in compression equipment. [M. E Aulton, Pharmaceutics, The Technology of Dosage Form Design, Second Model, 2002, pp. 441-448]
According to Biju et al 2004, [BIJU, S. S. ; SAISIVAM, S. ; RAJAN, M. G. ; MISHRA, P. R. Dual layered erodible microcapsules for revised release of Diclofenac sodium. Eur. J. Pharm Biopharm. , v. 58, n. 1, p. 61-67, 2004. ] enteric polymer approach is safe and widely used in medication products. Enteric covering prefers small intestine so it prevents the disintegration of tablet in the acidic environment of stomach and release into small intestine for some reasons such as
Prevention of acid attack on effective constituents at low pH
Protect abdominal from irritation from drug
Facilitate absorption of medicine which is preferentially utilized distal to tummy.
Most widely used enteric layer polymers are Cellulose acetate phthalate, Polyvinyl acetate phthalate, suited acrylic derivatives and Hydroxypropyl methyl cellulose phthalate because they're clear of carboxylic acid group and various pH solubility account. They may be almost insoluble at low pH and boosts solubility at specific pH such as pH 5. 2 for cellulose acetate phthalate. Enteric finish can be done for both sugar and film covering.
Peters et al, 1993[PEETERS, R. ; KINGET, R. Film-forming polymers for colonic medication delivery: I Synthesis and physical and chemical properties of methyl derivatives of Eudragit S. Int. J. Pharm. , v. 94, n. 1-3, p. 125-134, 1993. ] explained that there are amount of polymers are available that happen to be insoluble at low pH but dissolve at pH around or below 7. Shellac ia natural enteric polymer which is gastric amount of resistance. Hydroxypropyl methyl cellulose was initially polymer in contract to ethyl cellulose which can be used a book enteric coating brokers for acid security since it is normal water soluble and leach of film finish which diffuses medication more rapidly than ethyl cellulose. [ Kokubo et al, 1997, Gunder, Lippold, 1995]. [ KOKUBO, H. ; OBARA, S. ; MINEMURA, K. ; TANAKA, T. Development of cellulose derivatives as novel enteric layer realtors soluble at pH 3. 5-4. 5 and higher. Chem. Pharm. Bull. (Tokyo), v. 45, n. 8, p. 1350-1353, 1997. , GUNDER, W. ; LIPPOLD, B. H. ; LIPPOLD, B. C. Release of drugs from ethyl cellulose microcapsules (diffusion pellets) with pore formers and pore fusion. Eur. J. Pharm. Sci. , v. 3, n. 12, p. 203-214, 1995. ] A continuous technology finish is use to drinking water instead of organic and natural solvents to reduce environmental and protection dangers so Baudoux et al 1990, [BAUDOUX, M. ; DECHESNE, J. P. ; DELATTRE L. Film Covering with Enteric Polymers from Aqueous Dispersions. Pharm. Technical. Int. , v. 12, n. 11, p. 18-26, 1990. ] explained that water based technology has been widely used rather than organic and natural system.
After production, tablets must be evaluated to check on qualitative and quantitative analysis and chemical, physical and bioavailability properties. Because of this, evaluation is classified in three different categories.
Size and shape
Unique id markings
Organoleptic properties such as coloring, odour and flavor.
Brittle fracture index
Active drug content in tablet
Dissolution and disintegration
These evolution lab tests are specific standard in each pharmacopeia. Specification may be vary to 1 country from other. All products have regulatory aspects which must be complied for that particular product.