Excipients are inactive substances used in the formulation of tablets to provide bulk, improve stability, aid in drug release, or enhance patient acceptability. Although they do not have any therapeutic effect, they play essential roles in the manufacturing and performance of the tablet. The key categories of excipients include:

  1. Diluents (Fillers): Used to increase the volume of the tablet so that it can be easily handled and compressed. Common diluents include lactose, microcrystalline cellulose, and dicalcium phosphate.

  2. Binders: These help bind the tablet ingredients together to ensure that the tablet remains intact during handling. Examples include starch, polyvinylpyrrolidone (PVP), and hydroxypropyl methylcellulose (HPMC).

  3. Disintegrants: Disintegrants facilitate the breakup of a tablet after administration, ensuring that the drug is released for absorption. Common disintegrants include croscarmellose sodium, sodium starch glycolate, and crospovidone.

  4. Lubricants: Lubricants are used to reduce friction during the tablet manufacturing process, aiding in the release of the tablet from the die cavity. Magnesium stearate and stearic acid are frequently used lubricants.

  5. Glidants: These improve the flow properties of the powder mixture, making it easier to fill dies uniformly. Examples include colloidal silicon dioxide and talc.

  6. Coating Agents: Used to enhance appearance, improve taste, or control the release of the drug. Coatings may include film-forming agents such as hydroxypropyl methylcellulose or enteric coatings like cellulose acetate phthalate.

  7. Sweeteners and Flavoring Agents: Used to mask the unpleasant taste of some drugs, making them more acceptable to patients. Common examples include saccharin and sucralose.

  8. Colorants: Added to improve the appearance of the tablet and aid in product identification. FDA-approved dyes and pigments are commonly used.

Excipients are carefully chosen based on their compatibility with the active pharmaceutical ingredient (API) and their influence on tablet properties such as dissolution, stability, and bioavailability.