Tablet dosage forms is a dosage form in solid form ,each tablet consists of a unit dose of one or more active ingredients medicament . Tablets dosage form is intended for oral administration. where as some tablets are swallowed whole or after being chewed, some are dissolved dispersed in water before taken internaly, and some are retained in the mouth where the active ingredient is liberated
eg. Glyceryl trinitrate Sublingual tablets which is given in emergency for angina pectoris .
Drugs which are intended for administration by other routes, for example, in the form of implants and pessaries, may also be presented in the form of tablets these formulations may require special formulations, method of manufacture or form of presentation appropriate to the particular use they may not comply with all the requirements of official monograph of tablets.
Tablets are manufactured by method of compression of uniform volumes of powders or granules by compressing under high pressures and using punches and dies punches and dies requires special treatments to bare the pressure . The granules to be compressed contains of one or more medicaments, with or without excipients , substances such as diluents, binders, disintegrating agents, lubricants, glidants and substances capable of modifying the behaviour of the medicaments in the digestive tract. Such substances must be innocuous and therapeutically inert in the quantities present.
Because of their composition, method of manufacture and intended use, tablets present a variety of characteristics and consequently there are several categories of tablets.
Unless otherwise stated in the individual monograph of respective pharmacopoea , tablets are uncoated. Where coating is permitted the monograph states "The tablets may be coated". Where the monograph directs coating the statement reads "The tablets are coated". Unless otherwise directed, tablets may be coated in one of different ways.
General characteristics of Tablets dosage form : Tablets are usually solid, circular cylinders, the end surfaces of which are flat or convex and the edges of which may be bevelled. Tablets dosage form may exist in other shapes like triangular, rectangular, etc also. Tablets dosage form may have lines or break-marks and may bear a symbol or other markings. Tablets dosage form are sufficiently hard to withstand handling without crumbling or breaking.
Uncoated Tablets dosage form: Uncoated tablets may be single layer tablets resulting from a single compression of granules or multi-layer tablets consisting of parallel layers obtained by successive compression of granules of different compositions colour. No treatment is applied to such Tablets dosage form after compression. Any added substances are not specifically intended to modify the release of their active ingredient(s) in the digestive fluids.
The addition of colouring or flavouring agents to uncoated tablets other than multi-layer tablets is not official unless permitted in the individual monograph. Uncoated Tablets dosage form have the general characteristics of tablets. When a broken section of an uncoated tablet is examined under a lens, either a relatively uniform texture (single-layer tablets) or a stratified structure (multi-layer tablets) is seen; there are no signs of coating.
Coated Tablets dosage form: Coated tablets are tablets covered with one or more layers of mixtures of various substances such as resins, gums, inactive and insoluble fillers, sugars, plasticisers, polyhydric alcohols, waxes,. Coating may also contain medicaments. In compression-coated tablets, the coating is applied by compressing around the tablets granules prepared from tablet excipients such as lactose, calcium phosphate, etc. Substances used as coatings are usually applied as a solution or suspension in conditions in which evaporation of the vehicle takes palce. When the coating is thin, the tablets are described as film-coated.
Coated Tablets dosage form may contain flavouring and or one or more colouring agents permitted under the Drugs and Cosmetics Rules,
Coated tablets have a smooth, usually polished and often coloured, surface; a broken section examined under a lens shows a core surrounded by one or more continuous layers of a different texture.
Enteric-coated Tablets dosage form: Enteric-coated tablets (Gastric-resistant tablets) are tablets covered with one or more layers of coatings intended to resist the gastric fluid but to release their active ingredients in the intestinal fluid. For this purpose substances such as cellulose acetate phthalate and anionic copolymers of methacrylic acid and its ethers are used for providing tablets with a gastric-resistant coating or for covering either granules or particles with gastric-resistant coating.
Enteric-coated tablets have the characteristics of Coated Tablets dosage form.
eg-Diclofenac sodim tablets
Diclofenac sodium is a acidic drug and is better absorbed through lower inestine so it has to be formulaed as enteric coated tablets.
Dispersible Tablets dosage form: Dispersible tablets are uncoated tablets that produce a uniform dispersion in water and may contain permitted colouring matter and flavouring agents.
However addition of saccharin or its salts is not permitted in the preparation meant for paediatric use
Modified-release Tablets dosage form: Modified-release tablets (Sustained-release tablets) are coated or uncoated tablets containing auxiliary substances or prepared by procedures that, separately or together, are designed to modify the rate or the place at which the active ingredient is released.
Soluble Tablets dosage form: Soluble tablets are uncoated tablets that dissolve in water. The solution produced may be slightly opalescent due to added substances used in the manufacture of the tablets.
Effervescent Tablets dosage form: Effervescent tablets are uncoated tablets generally containing acidic substances and either carbonates or bicarbonates which react rapidly in the presence of water to release carbon dioxide. They are intended to be dissolved or dispersed in water before administration.
Tablets dosage form for Use in the Mouth: Tablets for use in the mouth are usually uncoated tablets formulated to be chewed or to effect a slow release and local action of the active ingredient (lozenges) or the release and absorption of the active ingredient under the tongue (sublingual tablets). Chewable tablets and lozenges may contain flavouring agents
eg.Drugs which are requred to give effect in mouth , lozenges for mouth ulcers ,deodarant
WHAT ARE THE BASIC STANDARD REQUIREMENTS OF TABLET DOSAGE FORM
Uniformity of container contents for tablets dosage form:
Tablets comply with the test for contents of packaged dosage forms, content of active ingredients: Determine the amount of active ingredient(s) by the method described in the Assay and calculate the amount of active ingredient(s) per tablet. The result lies within the range for the content of active ingredient(s) stated in the monograph. This range is based on the requirement that 20 tablets, or such other number as may be indicated in the monograph, are used in the Assay. Where 20 tablets cannot be obtained, a smaller number, which must not be less than 5, may be used, but to allow for sampling errors the tolerances are widened in accordance standards in pharmacopoea . The requirements of standards in pharmacopoea apply when the stated limits are between 90 and 110%. For limits other than 90 to 110%, proportionately smaller or larger allowances should be made.
Uniformity of weight of tablets: This test is not applicable to coated tablets other than film-coated tablets and to tablets that are required to comply with the test for uniformity of content for all active ingredients.
Weigh 20 tablets selected at random and calculate the average weight. Not more than two of the individual weights deviate from the average weight by more than the percentage shown in Table 2 and none deviates by more than twice that percentage.
weight variation limits
Average weight of tablet =Percentage deviation
80 mg or less =10 %
More than 80 mg but less then 250 mg= 7.5 %
250 mg or more =5 %
Uniformity of content of tablets : This test is applicable to tablets that contain less than 10 mg or less than 10% w/w of active ingredient. For tablets containing more than one active ingredient carry out the test for each active ingredient that corresponds to the aforementioned conditions.
The test for Uniformity of content should be carried out only after the content of active ingredient(s) in a pooled sample of the tablets has been shown to be within accepted limits of the stated content.
The test for Uniformity of content is not applicable to tablets containing multivitamins and trace elements.
Determine the content of active ingredient(s) in each of 10 tablets taken at random using the method given in the monograph or by any other suitable analytical method. The tablets comply with the test if not more than one of the individual values thus obtained is outside the limits 85 to 115% of the average value and none is outside the limits 75 to 125% of the average value. If two or three of the individual values are outside the limits 85 to 115% of the average value and none is outside the limits 75 to 125%, repeat the determination using another 20 tablets. The tablets comply with the test if in the total sample of 30 tablets not more than three of the individual values are outside the limits 85 to 115% and none is outside the limits 75 to 125% of the average value.
Disintegration test for Tablets dosage form: This test is not applicable to modified-release tablets and tablets for use in the mouth. For those tablets for which the dissolution test for tablets and capsules, is included in the individual monograph, the test for Disintegration is not required.
Uncoated Tablets: Comply with the disintegration test for tablets and capsules,. Unless otherwise directed in the individual monograph, use water as the medium and add a disc to each tube. Operate the apparatus for 15 minutes unless otherwise directed.
Coated Tablets: Comply with the disintegration test for tablets and capsules,. Unless otherwise directed in the individual monograph, use water as the medium and add a disc to each tube. Operate the apparatus for 30 minutes for film-coated tablets and for 60 minutes for other coated tablets unless otherwise directed in the individual monograph. For coated tablets other than film-coated tablets, if any of the tablets have not disintegrated, repeat the test on a further 6 tablets, replacing the water in the vessel with 0.1M hydrochloric acid. The tablets comply with the test if all 6 tablets have disintegrated in the acid medium.
Enteric-coated Tablets: Comply with the disintegration test for tablets and capsules,. If the tablet has a soluble external coating, immerse the basket in water at room temperature for 5 minutes. Suspend the assembly in the beaker containing 0.1M hydrochloric acid and operate without the discs for 120 minutes, unless otherwise stated in the individual monograph. Remove the assembly from the liquid. No tablet shows signs of cracks that would allow the escape of the contents of disintegration, apart from fragments of coating. Replace the liquid in the beaker with mixed phosphate buffer pH 6.8, add a disc to each tube and operate the apparatus for a further 60 minutes. Remove the assembly from the liquid. The tablets pass the test if all six have disintegrated.
Dispersible and Soluble Tablets: Disintegrate within 3 minutes when examined by the disintegration test for tablets and capsules, using water at 24o to 26o, unless otherwise stated in the individual monograph.
Effervescent Tablets: Place one tablet in a 250-ml beaker containing water at 20o to 30o; numerous gas bubbles are evolved. When the evolution of gas around the tablet or its fragments has ceased the tablet shall have disintegrated, being either dissolved or dispersed in the water so that no agglomerates of particles remain. Repeat the operation on a further 5 tablets. The tablets comply with the test if each of the 6 tablets disintegrates in the manner prescribed within 5 minutes, unless otherwise stated in the individual monograph.
Uniformity of dispersion of tablets : This test is applicable only to Dispersible Tablets.Place 2 tablets in 100 ml of water and stir gently until completely dispersed. A smooth dispersion is obtained which passes through a sieve screen with a nominal mesh aperture of 710 m m (sieve number 22).