DEFINITION TYPES AND STANDARD TESTS:
Tablets are unit, solid dosage forms, containing one or more active ingredients for oral administration. Tablets also contain additives like binders, diluents, disintegrating agent lubricants, glidents and other material for coating of tablets. Some material to form complex with active ingredients for controlled release of active ingredients after administration are also added in formulations. Organoleptic agents like, Permitted colouring, Flavouring and Sweetening agents are also added where ever required. Tablets are swallowed whole with water, milk or other suitable liquids, some are chewed and swallowed, some are dissolved or dispersed in water before administration and some are retained in mouth release of drug. Pessaries and Implants administrated by other than oral routes are also presented in tablet form, but these requires special requirements for formulation, Method of manufacturing and presentation for particular use they may not comply with all the requirements of the tablets.
There are several categories of tablets; Major types of tablets are given below:
1) Core Tablets or Uncoated Tablets: These are single or double layer, uncoated tablets are compressed tablets. No other treatment is applied to such tablets. The addition of colouring or flavouring agents to uncoated tablets other than multilayer tablets is not official unless permitted in the individual monograph of Official Books and Pharmacopoeias.
2) Coated Tablets: One or more layer of mixture of various substances such as, resin, gum and insoluble fillers, sugars, plasticizers, polyhydric alcohols, waxes etc. are applied to the core tablets. Some special cases coating may also contain active ingredients.
Film Coated Tablets: When the coating is thin the tablets are described as film-coated.
Sugar Coated Tablets: When sugar solutions with other additives are used for coating. Coating is called as sugar coating.
Coated tablets may contain flavouring and or one or more permitted colouring agents.
Coated tablets have a smooth, usually polished and often coloured surface. A broken section examined under a lens shows a core surrounded one or continuous layer of a different texture.
3) Enteric Coated Tablets: Enteric coated tablets are tablets covered with one or more layers of coating intended to resist the gastric fluid but to release their active ingredients in the intestinal fluid. For this CAP (Cellulose Acetate Phthalate) and anionic copolymers of methacrylic acid and its ethers are used for providing tablets with a gastric resistant coating.
4) Dispersible Tablets: Dispersible tablets are uncoated tablets that produce a uniform dispersion in water and may contain permitted colouring and flavouring agents.
5) Modified Release Tablets: These are sustained release, coated, uncoated tablets containing other additives and prepared by procedure that, separately or together, are designed to modify the rate or the place at which the active drug is released.
6) Soluble Tablets: These are uncoated tablets that are dissolved in water.
7) Effervescent Tablets: These are uncoated tablets generally containing acidic substances and either carbonate or bicarbonates which react rapidly in the presence of water to release carbon-di-oxide. They are dissolved or dispersed in water before administration.
8) Lozenges and Sublingual Tablets: These are tablets for use in mouth and are usually uncoated and formulated to be chewed or to effect a slow release and local action of active ingredients (Lozenges) or the release and absorption of the active ingredients under the tongue (Sublingual tablets) e.g. Nitro-glycerine tablets for Angina Pectoris.
1. Description: Tablets are usually solid right circular cylinders, the end surfaces of which are flat or convex and edges may be bevelled. They may have lines or break lines or break mark and may bear a symbol or other marking. They may exit in other shapes like triangular, rectangular etc. For safe handling they should be sufficiently hard.
2. Uniformity of Container Content: The average number of the contents of the content of 10 containers is not less than the labelled amount and the number in any single container is not less than 98% and not more than 102% of the labelled amount.
3. Content of Active Ingredients: Limit 90 to 110%. (samples of 20 tablets)
4. Uniformity of Weight: Not more than two of the individual weights deviate from the average weight by more than % shown below and none deviates by more than twice that %.
Above is the % deviation for average and not for individual weight, for individual weight 2% deviation may be considered or fixed after validation.
5. Uniformity of Content: This is applicable to tablets that contain less than 10mg or less than 10% of active ingredients. This test is not applicable for Multivitamin and Trace element tablets. The tablets comply with the test if not more than one of the individual valves obtained from 10 containers is outside the limits 85% to 115% of average value and none is outside the limits 75% to 125% of average values.
a) Uncoated Tablets: Tablets should disintegrate within 15 minutes by using water as medium.
b) Film Coated Tablets: Tablets should disintegrate within 30 minutes by using water as medium and adding disc to each tube. (Water Temperature.37°± 2°C)
c) Other Coated Tablets: Tablet should disintegrate within 60 minutes by using water is medium and adding disc to each tube. (Water Temperature.37°± 2°C)
d) Enteric Coated Tablets: Tablets should not shows sign of disintegration for 120 minutes in Acidic Medium (0.1m hydrochloric acid) without disc and tablets should disintegration within 60 minutes in mixed phosphate buffer medium (pH6.8) with addition of disc.(Temperature.37°± 2°C).
e) Dispersible and Soluble Tablets: Disintegrate within 3 minutes using water as medium at 24 to 26°C temperature.
f) Effervescent Tablets: Limit – within 5 minutes in Beaker containing water at 20 to 30°C.
7. Uniformity of Dispersion:
This test is applicable for dispersible tablets. Place 2 tablets in 100ml 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 micron meter (Sieve No.22).
8. Dissolution Test:
Testing stages and Acceptance limits as per IP 1996:
9. Hardness Test: Limit not less than 4 kg per cm.sq.
10. Friability Test: Limit not more than 2% by using friabilator.
11. Identification, Assay and Other Special Tests: Shall comply with specifications.