Main Components of a Capsule Formulation

1. Active Pharmaceutical Ingredient (API)

The Active Pharmaceutical Ingredient (API) is the primary medicinal component of the capsule formulation. It is
the substance responsible for the intended therapeutic effect. The API can exist in different forms, such as
solids, liquids, or semi-solids, depending on the drug’s properties. The dosage strength of the capsule is
determined by the concentration of the API present in each unit.

2. Excipients

Excipients are inactive substances added to the capsule formulation alongside the API. They serve various purposes,
including aiding in the manufacturing process and enhancing the performance of the final product. Common excipients used in capsule formulations include:

• Fillers and Diluents: These excipients add bulk to the capsule, ensuring that the correct
  amount of API is present in each dosage unit. Examples include lactose, microcrystalline cellulose, and starch.
• Binders: Binders are used to hold the powdered ingredients together, maintaining the
  integrity of the capsule and preventing premature disintegration. Common binders include starch, gelatin, and
  cellulose derivatives.
• Lubricants: Lubricants reduce friction between the formulation components and the capsule
  shell, facilitating smooth capsule filling and swallowability. Examples include magnesium stearate and stearic
  acid.
• Disintegrants: Disintegrants promote the rapid disintegration of the capsule in the
  gastrointestinal tract, allowing for efficient drug release and absorption. Common disintegrants include
  croscarmellose sodium, cross povidone, and sodium starch glycolate.
• Colorants: Colorants are added to the formulation for visual identification and branding
  purposes. They do not affect the capsule’s therapeutic properties.

3. Capsule Shell

The capsule shell is the outer covering that encloses the API and excipients in a solid dosage form. There are two
main types of capsule shells:

• Gelatin Capsules: Made from gelatin, a protein derived from animal collagen, gelatin
  capsules are available in various sizes and colors. They can accommodate both solid and liquid formulations.
• Vegetable Capsules: Vegetable capsules are composed of cellulose derivatives, making them
  suitable for vegetarians and individuals with dietary restrictions. Similar to gelatin capsules, they are
  available in various sizes and colors.

The selection of the appropriate capsule shell depends on the formulation’s compatibility with the shell material
and any specific dietary or cultural considerations.

In conclusion, a capsule formulation consists of an active pharmaceutical ingredient (API), excipients that aid in
formulation and performance, and the capsule shell that encloses the contents. Each component’s careful selection
and formulation are vital in ensuring the capsule’s efficacy, stability, and overall quality.