Formulation of tablets: Compressed tablets, Excipients (Additives or Pharmaceutical aids), Diluents, Granulating Agents, Binders, Disintegrating Agents, Lubricants, Organoleptic Agents: Colouring Agents, Flavouring Agents, Sweetening Agents.

• Formulation of tablets

Compressed tablets consist of medicaments and excipients (additives or pharmaceutical aids). Excipients are pharmacologically inert substances that facilitate the manufacturing of dosage form and their stability and bioavailability.

The following excipients are used in the manufacturing of compressed tablets.

• 1. Diluents

• 2. Granulating agents

• 3. Binders

• 4. Disintegrating agents

• 5. Lubricants,

• 6. Organoleptic agents: Colouring agents, Flavouring agents, Sweetening agents

DILUENTS

Diluents (Fillers) are pharmacologically inactive ingredients added in tablet formulation to increase bulk medicaments. Examples are lactose, starch, sucrose, mannitol, microcrystalline cellulose, calcium carbonate, calcium sulfate, calcium phosphate, etc. Diluents are used in the following conditions

• a. Dose of medicaments is too small and cannot be compressed as a tablet.

• b. To ensure the desirable size and shape of a tablet.

• c. To make it easy to pack and handle compressed tablets.

• d. Granulating agents

GRANULATING AGENTS

Granulating agents are used to convert fine powders of medicament and other additives into granules. Examples are starch mucilage, water, isopropyl alcohol, acetone, acacia mucilage, tragacanth mucilage, etc.

DISINTEGRATING AGENTS

Disintegrating agents facilitate the breakdown of the tablet into smaller particles after its ingestion. The main purpose of tablet disintegration is to increase the dissolution of medicaments inside GIT and to increase its rate of absorption. Examples are starch, microcrystalline cellulose, sodium starch glycolate, ion exchange resins, etc. A selection of disintegrating agents depends upon the required disintegration rate of tablets.

Mechanism of disintegration:

• 1. Swelling: Disintegrating agents absorb moisture or water from surroundings to swell. This swelling causes the disintegration of tablets into granules and then into smaller particles. Starch acts by this mechanism. Potato starch is superior to maize starch as a disintegrating agent. But maize starch is commonly used due to its cheap rate.

• 2. Effervescence: Disintegrating agents react in the presence of moisture or water to release gas. This gas produces effervescence that disintegrates tablets. Example mixture of sodium bicarbonate, tartaric acid, and citric acid.

• 3. Melting: Some disintegrants melt at body temperature to release medicaments from tablets. Example: Cocabutter.

Addition of disintegrants in the formulation: Disintegrants are divided into two parts. The first part is mixed with powder ingredients before granulation. The second part is mixed in granules after its drying and before granules compression. This breaks the tablets into granules and then granules into smaller particles.

LUBRICANTS:

Lubricants reduce friction between two surfaces. Lubricants are added in tablet formulation to increase the flow ability of granules, and to prevent stickiness of tablets with dies and punches. Depending upon their actions, lubricants are divided into the following three categories

• 1. Lubricants: They reduce particular frictions and friction between tablets and dies. This facilitates the flow of granules from the hopper to the die and the ejection of tablets from the die after compression. Examples are magnesium state and calcium stearate.

• 2. Glidants: They reduce friction between granules and hopper walls. This facilitates the flow of granules from hopper to die. It ensures complete filling of dies during tablet compression. Examples are talc, boric acid, starch, calcium stearate, etc.

• 3. Anti-adhesive agents: They prevent the stickiness of tablet surfaces with dies and punches during tablet compression. Selection and amount of lubricants affect the disintegration of tablets.

• 4. Organoleptic agents: Organoleptic agents are used to improve the appearance of tablets, acceptance among patients, and make tablets more pleasant. Coloring agents, flavoring agents, and sweeteners are used as organoleptic agents.

  • a. Colouring agents: They impart color to tablets to improve their elegance. Coloring agents are mixed with the vehicle of a granulating agent or with powder ingredients before their mixing. Mixing of coloring agents with granulating fluid imparts uniform color to tablets. Coloring agents are used to distinguish different types of tablets and to improve tablets' elegance. Only drug administration-certified coloring agents shall be used as coloring agents for tablets.

  • b. Flavouring agents: Flavouring agents are mainly used in lozenges, effervescent tablets, and chewable tablets. Flavouring agents are volatile ingredients thus they are added into granules just before granulation. Flavoring agents are dissolved in organic solvent and sprayed over granules just before the compression of tablets.

  • c. Sweetening agents: Sweetening agents are used mainly in lozenges and chewable tablets. It is used to mask the bitterness of medicaments and improve the taste of tablets. Examples are sucrose, mannitol, lactose, etc.

Alok Bains