Common Excipients Used in Tablet
Manufacturing
It is well known that excipients are the important elements or components of any solid oral dosages forms. Although these excipients are called inert materials or inactive substances but they play a major role in the manufacturing of tablet dosage forms. These excipients are added in the manufacturing of the tablet for providing the desired bulk to the tablet so that the tablet can be compressed easily without any wear and tear of compression machine tools. It also improves the working conditions of the machines.
Must Read: Solid oral dosage forms (Tablet or Capsules)
These excipients include diluents, binders, glidants, lubricants, disintegrants, coloring agents, and flavoring agents. These excipients can be classified as per the role they play while manufacturing the tablet dosage forms.
Must Read: What are tablet dosage forms?
The excipients like diluents, binders, lubricants, and glidants play their role During the tablet compression method and tablet processing is performed. While disintegrants, coloring agents, flavoring agents, Sweetening agents, and surfactants play their role to provide the physical characteristics of the finished tablet dosage forms. As per the requirement to improve the stability and the shelf life of tablet dosage forms antioxidants can be added during the production of tablets or solid oral dosage forms.
To enhance the stability, bioavailability, and process through which the solid dosage forms are prepared can be studied or shown by the pre-formulation studies.
Diluents:
The amount of active pharmaceutical ingredients (API) is not in enough quantity for the compression of the tablets means the active ingredients are very small in size then these inert materials are used to provide sufficient bulk to make the tablet in the desired size for compression. These inert or inactive substances are known as Diluents.In direct compression methods, these diluents give excellent compressibility and flowability.
To avoid bioavailability problems while preparing a tablet with an active drug with low water solubility, water-soluble diluents should be used.
By taking a very simple example of the compressed tablet of diclofenac sodium 50 mg. It is well known that only diclofenac sodium is not enough to compress and convert into a tablet, there is required to add some bulking agents to make them in the form of desired shape and size.
Examples of Diluents:
- Lactose
- Microcrystalline cellulose
- Dextrose, glucose
- Sucrose
- Starch and derivatives
- Calcium carbonate
- Dicalcium phosphate
- Magnesium carbonate
Binders:
Binders are also known as Adhesives. Binders are the most important excipients to add tablet dosage forms.Binders are substances that promote cohesiveness. These binders are used for converting the powder into granules through a process which is called granulation.
During the compression process, many times tablets remain intact in the dies or punches. Due to the use of binders this problem can be overcome.
The binders also improve the free-flowing quality of granules.
The Characteristics of compressed tablets totally depend upon how much quantity of binders is used in the tablet preparation. If too much binder is used then the finished tablet will become very hard that will not easily disintegrate and also be responsible for the wear and tear of dies and punches.
Binders can be used either in the dry form or in the form of solutions depending upon their formulations and method of preparation of tablet dosage form.
Examples of Binders:
| Binder | Normal usage concentration (%) |
|---|---|
| Starch | 5–25 |
| Pregelatinized starch | 5–10 |
| Acacia | 1–5 |
| Polyvinylpyrrolidone (PVP) | 2–8 |
| Hydroxypropyl methylcellulose (HPMC) | 2–8 |
| Methylcellulose (MC) | 1–5 |
Lubricants:
These are the substances that prevent the adhesion of tablet material to reduce the friction between dies and punches and facilitate easy ejection of tablets from the die cavity and also improve the flow rate of granules. The quantity of lubricants varies from 0.1 to 5%.It is being noticed that after compression many tablets have a tendency to expend and it binds and sticks to the side of the die wall. So, it is very important to choose a proper lubricant that will overcome it very effectively.
The method of addition of lubricants to the granulation is also very important. After the addition of lubricants, the granulation is mixed very gently so that lubricants distribute into all granules without breaking them into fine particles.
Examples of Lubricants:
| Lubricant | Level required (%) |
|---|---|
| Magnesium stearate | 0.2–2.0 |
| Calcium stearate | 0.5–4.0 |
| Sodium stearyl fumarate | 0.5–2.0 |
| Polyethylene glycol 4000 and 6000 | 2–10 |
| Sodium lauryl sulfate | 1–3 |
| Magnesium lauryl sulfate | 1–3 |
| Sodium benzoate | 2–5 |
Glidants:
The glidants enhance or improve the flow characteristics of a powder. Glidants are always added in the dry state just before the compression of the tablet dosage forms. Glidants are used in concentrations of less than 1%.Examples of Glidants:
| Glidant | Typical percentage |
|---|---|
| Talc | 1-5 |
| Fumed silicon dioxide | 0.1-0.5 |
| Starch | 1-10 |
| Calcium silicate | 0.5-2.0 |
| Magnesium carbonate (heavy) | 1-3 |
| Magnesium oxide (heavy) | 1-3 |
| Magnesium lauryl sulfate | 0.2–2.0 |
| Sodium lauryl sulfate | 0.2–2.0 |
Disintegrants:
Disintegrants are substances added into tablet manufacturing to make easy it to disintegrate or break up after administration in the body. Corn and potato starch is one of the oldest disintegrants.Generally, disintegrants are mixed with active ingredients and diluents after the granulation process. But in some cases disintegrants are added in tablet manufacturing in two parts, one part is added before the granulation process and the remaining part is mixed with the lubricants and finally, both parts are mixed just before the compression process.
Examples of Disintegrants:
Disintegrant
Normal usage concentration (%)
Starch
5–10
Sodium starch glycolate
2–8
Croscarmellose sodium
1–5
Alginic acid, sodium alginate
4–6
Crospovidone
1–5
Coloring Agents:
In compressed tablets, colors play a very important role as they help in the identification. All the colorants which are used in the pharmaceuticals are certified and approved by the FDA.The method of addition of color to a tablet formulation is to dissolve the dye in the binding solution just before the granulating process starts.
Flavoring Agents:
Artificial sweeteners are used in the manufacturing of mouth-dissolving tablets and chewable tablets to mask or reduce the unpleasant taste of tablets.Examples of Flavoring Agents:
- Lactose
- Mannitol
- Aspartame etc.
The Excipients Used in the Tablet Must Meet Certain Criteria in the Formulation Such as;
- Excipients should be non-toxic.
- The cost of excipients should be low.
- The excipients should be physiologically inert.
- Excipients should be free of any unacceptable microbiologic load.
- The excipients should be color compatible ( not producing any off-color appearance)
- If the drug product is also classified as a food (e.g. certain vitamin products), the diluents and other excipients must be approved directly to food additives.
Hence, while preparing a tablet dosage form the number of excipients used. These excipients should be used by proper information about their properties and by knowing about their limitations.
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