Tablet Excipients – Virtual Video Lessons in Hindi & English by Dr. Tarun Virmani

We provide this virtual lessons by Dr. Tarun Virmani, Associate Professor, MVN University, especially for our Indian Audience.

Drug products usually contain inactive, non-medicinal substances other than the therapeutic agent(s). These substances are called excipients, and they are intentionally included in a drug product to serve different pharmaceutical purposes, thus ensuring product acceptability in terms of manufacturability, appearance and performance.

In tablet formulation, excipients are usually combined at various quantities with the active drug substance(s) to produce tablets that are of standard quality. The type and quantities of each excipient used depend on the type of tablet desired and the process employed.Classes of excipients used in the manufacture of tablets
Excipients used in tablet formulation may be classified into two groups:

Those that help to impart satisfactory processing and compression characteristics to the formulation e.g. bulking agents/diluents, binders, glidants, and lubricants.
Those that help to give additional desirable physical characteristics to the compressed tablets e.g., disintegrants, surface acting agents/ surfactants, colours, flavours and sweetening agents (as in the case of chewable tablets), polymers or hydrophobic materials (as in the case of controlled-release tablets).
Excipients used in the formulation of tablets
Typically the following excipients/ ingredients are used in the manufacture of conventional tablets

i. Binders
Binders also referred to as granulators or granulating fluid, are polymeric, natural or synthetic materials that impart cohesive qualities to powdered materials used in tablet manufacture. They ensure the tablets remain intact after compression, as well as improve the free-flowing qualities of the powdered materials without retarding disintegration or dissolution.

Binders are used alone or in combination with one another. They are added as dry powders (e.g., cellulose and polyvinyl pyrrolidone) or in the form of their solution that is, by dissolving it in a suitable and appropriate solvent. The quantity used has considerable influence on the properties of the compressed tablets. The use of excessive binder will make a hard tablet that will not disintegrate easily when the tablet comes in contact with moisture and will also cause excessive wear of punches and dies.

Binders must be non-toxic and must have a good compatibility profile. Materials commonly used as binders include acacia gum, hydroxypropylmethylcellulose, tragacanth, polyvinyl pyrrollidone (PVP), corn starch, microcrystalline cellulose, etc.

Examples and concentrations of binders commonly used in tablet formulation

Binders used in tablet formulation
ii. Bulking Agents/ Diluents/ Fillers
These are approved excipients added to any tablet formular when the quantity of active pharmaceutical ingredient is very small. They are added to increase the size of the tablets to get a significant tablet weight that can be handled or compressed, thereby rendering the manufacturing process more reliable and reproducible. The quantity of bulking agent that appears in a formula is normally determined by the quantity of the drug, the nature and amount of other ingredients in the formulation.

Bulking agents must be approved like all other raw materials used in tablet formulation. They should be chemically inert, non-hygroscopic, hydrophilic and must exhibit good compression properties. The compatibility of the bulking agent with the drug substance must be considered as studies have shown that some interfere with the absorption of drug substances from the gastrointestinal tract e.g., calcium salts used as bulking agent for the broad-spectrum antibiotic tetracycline.

Lactose is a common bulking agent used in both tablet and capsule formulations as it fulfils most of the ideal characteristics of bulking agents. It is unsuitable for patients who are lactose intolerant. Other examples of bulking agents used in tablet manufacture include mannitol, dicalcium phosphate, calcium sulfate, dry starch, cellulose, kaolin, sodium chloride, anhydrous lactose, sorbitol, sucrose etc.

iii. Disintegrants
Disintegrants or disintegrating agents are raw materials that appear in some tablets. They are added to formulations to overcome the cohesive strength imparted during compression, thus facilitating the breakdown of the tablet into granules for ready drug availability once they come in contact with moisture. There is still a lack of understanding with respect to the mechanisms by which disintegrants elicit their functions.