By K . Madhuri Ist M.Pharmacy pharmaceutics TABLETS By K . Madhuri Ist M.Pharmacy pharmaceutics UNDER THE GUIDANCE OF DR. A.SEETHA DEVI M.PHARM., PHD.,

INTRODUCTION Tablet is a solid unit dosage form for oral administration.Tablets are the most popular among all the dosage forms. About two third drugs prescribed are in solid dosage form and tablets include half of them. Tablets are obtained by compression of uniform volumes of powders or granules by applying high pressure and using punches and dies.

DEFINITION Tablet is defined as a compressed unit solid dosage form containing medicaments with or without excepients. or Tablet represent unit dosage form in which one usual dose of the drug has been accura tely placed.

ADVANTAGES Cost is lowest of all oral dosage forms. Lighter and compact. Greatest dose precision and the least content variability. Easy to swallowing with least tendency for hang-up. Easiest and cheapest to package and ship.

DISADVANTAGES Difficult to swallow for children or unconscious patients. Some drugs resist compression in to dense compacts. Drugs with poor wetting , slow dissolution properties, may be difficult to formulate a tablet. Bitter taste drugs , drugs with an objectionable odor . In such cases , the capsule may offer the best and lowest cost approach.

PROPERTIES OF TABLETS Should be an elegant product. Should have the strength. Should have the chemical and physical stability. Must be able to release the medicament. Must have a suitable chemical stability over time so as not to allow alteration of the medical agent.

A . TABLETS INGESTED ORALLY 1 . COMPRESSED TABLETS 2 . MULTICOMPRESSED TABLETS

4 . Sugarcoated tablets 5 . Film coated tablets

B . Tablets used in oral cavity 2 . Troches or lozenges 1 . Sublingual tablet

Tablets administered by other routes: Implantable tablets : These are designed for subcutaneous implantation in animals or man. To provide a constant drug release rate. Small , cylindrical or rosette-shaped forms. Length is not more than 8mm. Vaginal tablets : These are designed to undergo slow dissolution and release in the vaginal cavity. Ex : Clotrimazole tablets.

Tablets used to prepare solutions: 1 . Effervescent Tablets 2 . Hypodermic Tablets

3 . Dispensing tablets 4 . Tablet triturates

Techniques for granulation Direct compression : Blending the dry powdered ingredients together , and then compressing in to tablets. Wet granulation : A pharmaceutical glue called a binder is put in to water or a solvent system and is sprayed or metered in to powders. Dry granulation : Use mechanical force to densify and compact powders together which forms dry granules.

Wet granulation Wet granulation is a process of using a liquid binder to lightly agglomerate the powder mixture. The amount of liquid has to be properly controlled, will cause over-wetting will cause the granules to be too hard and under-wetting cause them to be too soft and friable . Aqueous solutions have the advantage of being safer to deal with than solvent-based systems but may not be suitable for drugs which are degraded by hydrolysis.

In this process , powder is fed to a product container and then moistened or sprayed with molten material in order to increase the cohesive forces. The liquid can be water or an organic solvent , if necessary with binder. At the same time , the ingredients are mixed together vigorously.

Dry granulation Dry granulating, also called Slugging, Chilsonating or Roller compaction, involves the pressing of mixed powders into an object to be reground into a precise powder. This action increases particle density, improves powder flow and captures fines. Powders can be compacted using a tablet press; this is called Slugging. Once slugging is completed or powders are compacted on a Chilsonator or Roller Compactor, they are milled.

The dry granulating method is used over other technologies for one or more reasons : Granulating materials which are sensitive to heat and or moisture. Produce a uniform particle size range. Improve flow properties. Control dust. Control bulk density. Produce uniform blends. Control particle hardness. Improve wetting or dissolution rates.

Direct compression In early days, most of the tablets require granulation of the powdered Active Pharmaceutical Ingredient (API) and Excipients. At the availability of new excipients or modified form of old excipients and the invention of new tablet machinery or modification of old tablet machinery provides an ease in manufacturing of tablets by simple procedure of direct compression.

Among the tehniques used to prepare tablets , direct compression is the most advanced technology. It involves only blending and compression. Thus offering advantages particularly in terms of speed production. Because it requires fewer unit operations , less machinery , reduced number of personnel , considerably less processing time along with increased product stability.

Limitations Stratification – poor content uniformity. Interaction. Large dose drugs (30%). Static charge.

Different punches

PROCESSING PROBLEMS OF TABLETS Capping and Lamination Picking and Sticking Mottling Weight variation Hardness variation Drug instability Double impression

CAPPING AND LAMINATION Partial or complete separation of the top or bottom crowns of a tablet from its main body. Lamination: Separation of tablet into two or more distinct layers.

Reasons: Air entrapment among the particles or granules . Over drying of granules. Deep concave punches. Incorrect setup at the press. Remedies: Use of sufficient amount of binder. Use of proper amount of fines . Use of sorbitol, methylcellulose, or PEG 4000. Use of flat punches. Maintaining the compression machine in a proper condition.

PICKING AND STICKING

Picking: Adhering to and removal of tablet material by the punch surface. sticking: Adhering of tablet material to die wall. Reason: Improperly dried granulation Inclusion of high quantity of low melting point substances, either active ingredients or additives such as stearic acid, Polyethylene glycol. Use of punches with improper faces.

Remedies: allowing the granulation to dry sufficiently. Adding an adsorbent i.e., silica aerogel, aluminium Decreasing the moisture content of the granulation, hydroxide, and MCC.

MOTTLING Mottling is an unequal distribution of color on a tablet, with appearance of light and dark areas on it. Reason: Use of drug whose color differs from that of the tablets excipients. Use of drugs whose degradation products are colored. Migration of dye to the surface of granulation during drying. Improper mixing of dye in direct compression formulations.

Remedies: WEIGHT VARIATION: Reasons: Changing the solvent system, reducing the drying temperature. Dye should be mixed properly. WEIGHT VARIATION: Weight of a tablet being compressed is determined by the amount of granulation in the die prior to compression. Reasons: Granule size and size distribution before compression: Variations in the sizes of granules.

Disadvantages of poor flow: Arching or bridging Rat holing The process of die filling process depends on uniform flow of granules from the hopper. Disadvantages of poor flow: Arching or bridging Rat holing Arching is segregation of fine particles at the neck of hopper. Rat-holing is segregation at sides of the hopper. Remedies to overcome poor flow: Using of high amount of glidants such talcum, colloidal silica. Using of induced die-feeders. but these may cause reduction in granule size.

HARDNESS VARIATION: Poor mixing: Remedy: Punch variation: Remedy: Improper distribution of lubricants and glidants. Remedy: Carry out mixing for 3min, but excess mixing during lubricant addition results in granule friability. Punch variation: Unequal length of lower punchs. Remedy: Using of tooling set with uniform dimensions. HARDNESS VARIATION: Hardness depends upon weight of material and the space between upper and lower punches at the movement of compression.

DRUG INSTABILITY: DOUBLE IMPRESSION: If granules are not properly dried, and if drug is moisture sensitive then drug become unstable. DOUBLE IMPRESSION: This problem arises when either lower or upper punches having the monogram. In tablet compression machines, the lower punch is free and rotates before the tablet is pushed off, resulting in double impression.

Evaluation of tablets Weight variation Content uniformity General appearance Size and shape Unique identification markings Organoleptic properties Hardness Friability Drug content and release Weight variation Content uniformity Disintegration test Dissolution test

REFERENCES: Pharmaceutical Dosage forms: TABLETS VOLUME 1 The Theory and Practice of Industrial Pharmacy by LEON LACHMAN, HERBERT A.LIEBERMAN, JOSEPH L.KANIG BENTLEY’S Textbook of Pharmaceutics. Edited by E.A.RAWLINS