TABLETS

TABLETS

The oral route of drug administration is the most important method of administering drugs for systemic effect. Nevertheless, it is probable that at least 90% of all drugs are used to produce systemic effect are administered by the oral route.

Tablet is the very popular dosage form administered orally and also other routes

DEFINITION:

Tablet is the solid unit dosage form-containing medicament with or without diluents prepared either by compression or by moulding.

TYPES AND CLASSES OF TABLETS:

Tablets are classified by their route of administration or function as follows.

1.       Tablets ingested orally

All over 90% of the tablets manufactured today are ingested orally.

o        Compressed tablets or standard compressed tablets.

o        Multiple compressed tablets.

o        Repeat-Action tablets.

o        Delayed-Action and Enteric coated tablets.

o        Sugar-and chocolate-coated tablets.

o        Film-coated tablets.

o        Chewable tablets.

2.       Tablets used in the oral cavity

o        Buccal and sublingual Tablets.

o        Troches and Lozenges

o        Dental cones.

3.       Tablets Administered by other Routes

o        Implantation Tablets.

o        Vaginal Tablets.

4.       Tablets used to prepare solutions

o        Effervescent Tablets.

o        Dispensing Tablets.

o        Hypodermic Tablets

o        Tablet Triturates.

POTENTIAL ADVANTAGES OF TABLETS

1.       They offer greatest dose precision and the least content variability.

2.       Their cost is lowest of all oral dosage forms.

3.       They are the lightest most compact of all oral dosage forms.

4.       They are in general easiest and cheapest to package and ship of all oral dosage forms.

5.       Product identification is potentially the simplest.

6.       They may provide the greatest ease of swallowing.

7.       They lend themselves to certain special release profile products, such as Enteric or Delayed-release products.

8.       They are better suited to large-scale production than other unit oral forms.

9.       They have the best-combined properties of chemical, mechanical and microbiologic stability of all the 10. Oral forms.

DISADVANTAGES OF TABLETS

·         Some drugs resist compression into dense compact owing to their amorphous nature or flocculent, low-density character.

·         Drugs with high doses are difficult to formulate as tablets.

·         Bitter tasting drugs and drugs with objectionable odour or drugs that sensitive to oxygen or atmospheric moisture m ay require special processing like coating or encapsulation which may increase the cost of the dosage form.

·         Drugs with poor wetting and slow dissolution properties are difficult to convert into tablets.

GRANULATION TECHNIQUES

1.      Dry manufacturing methods:

a.       Direct compression.

b.       Compression granulation.

                                                               i.      Slugging method.

                                                             ii.      Roller compression.

2.      Wet granulation method:

TABLET DESIGN AND FORMULATION

Regardless of how tablets are manufactured, Conventional oral tablets for ingestion
usually contain the same classes of components in addition to the active ingredients, which
are one more agents functioning as

·         Diluents

·         Binders and Adhesives

·         Disintegrants

·         Lubricants

·         Antiadherants

·         Glidants

·         Colors, Flavours and sweeteners

All non-drug component of a formula termed Excipients or Additives or Adjuants.

IDEAL PROPERTIES OF TABLET EXCIPIENTS:

·         They must be non-toxic.

·         They must be commercially available in an acceptable grade.

·         Their cost must be acceptably low.

·         They must not be contraindicated by themselves.

·         They must be physiologically inert.

·         They must be physically and chemically stable by themselves and in combination with the active ingredients and other tablet components.

·         They must free of any unacceptable microbiologic load.

·         They must be coloring compatible.

·         They must not have deleterious effect on the bioavailability of the drugs in the products

DILUENTS:

Diluents are fillers designed to make up the required bulk of the tablet when the drug dosage itself is inadequate to produce this bulk, and also to provide better tablet properties such as improved cohesion, to permit us direct compression manufacturing, or to promote flow

Ex: Lactose, Dire4ct compressible starches, dibasic calcium phosphate dehydrate, microcrystalline cellulose. Mannitol, Sorbitol, Dextrose, Hydrolyzed starches. Etc.

BINDERS AND ADHESIVES:

These materials are used either dry or in liquid form during wet granulation to glue the powder together and form granules or to promote cohesive compact for direct compressed tablets.

Ex: Acacia, Cellulose derivatives, Gelatin, Polyvinylpyrrolidon (PVP) Starch paste, Sodium alginate, Tragacanth, Etc.

DISINTEGRANTS:

A disintegrant is added to most of the formulations to facilitate a breakup or disintegration of the tablet when it contacts water in the gastrointestinal tract. Disintegrants may function by drawing water into the tablet, swelling, and causing the tablet to burst apart.

Ex: Starch, Veegum HV, Bentonite, Alginates, and cellulose. Etc.

LUBRICANTS:

Lubricants are intended to reduce the friction during the tablet ejection between the walls of
the tablet and the walls of the die cavity in which the tablet is formed.

Ex: Stearic acid, Stearic acid salts, Talc, Polyethylene glycols. Etc.

ANTIADHERENTS:

Antiadherents have the purpose of reducing sticking or adhesion of any of the tablet
granulation or powder to the faces of the punches or to the die wall.

Ex: Magnesium stearate, Talc, starch Etc.

GLIDANTS;

Glidants are intended to promote flow of the tablet6t granulation or powder materials by
reducing friction between the particles.

Ex: Silica derivatives, Talc, Cornstarch. Etc.

COLOURS, FLAVOURS AND SWEETENERS:

These are the optional components used for the special purposes. The use of colours and dyes in tablet making has served three purposes: disguising of off-colour drugs, product identification, and production of more elegant product. Flavours are usually limited to chewable tablets or other tablets intended to dissolve in the mouth. The use of sweeteners is primarily limited to chewable tablets.

Ex: FD & C and D & C dyes and lakes, Natural sweeteners, artificial sweeteners like saccharin and aspartame.

REFERENCE: The theory and practice of industrial pharmacy by Leon Lachman.