Starch is a polysaccharide carbohydrate consisting of a large number of glucose units joined together by glycosidic bonds.

As a diluent, starch is used for the preparation of standardized triturates of colorants, potent drugs, and herbal extracts, facilitating subsequent mixing or blending processes in manufacturing operations. Starch is also used in dry-filled capsule formulations for volume adjustment of the fill matrix, and to improve powder flow, especially when using dried starches. Starch quantities of 3–10% w/w can act as an antiadherent and lubricant in tableting and capsule filling.

In tablet formulations, freshly prepared starch paste is used at a concentration of 3–20% w/w (usually 5–10%, depending on the starch type) as a binder for wet granulation. The required binder ratio should be determined by optimization studies, using parameters such as tablet friability and hardness, disintegration time, and drug dissolution rate.

Moisture content All starches are hygroscopic and absorb atmospheric moisture to reach the equilibrium humidity.The approximate equilibrium moisture is characteristic for each starch. At 50% relative humidity:
• 12% for corn starch;
• 14% for pea starch,
• 18% for potato starch;
• 14% for rice starch;
• 13% for wheat starch.

Starch 1500 (Pregelatinized Starch)

It is a directly compressible, free flowing, USP grade of partially hydrolyzed cornstarch. It is prepared by subjecting cornstarch to physical compression or shear stress in high moisture conditions causing an increase in temperature and a partial gelatinization of some of the starch granules. The product is consists of about 5% free amylose, 15% amylopectin and 80% unmodified starch. It provides fair to good binding properties and dilution potential, but requires high pressures to produce hard tablets. It also produces a dense tablet with good disintegration properties. Starch 1500 exhibits self-lubricating property. It has poor flowability compared to other directly compressible adjuvants and shows higher lubricant sensitivity. It is also used as filler in capsule formulation.

Characteristics of Compressible Starch (Pregelatinized)

  • Pregelatinized starch is a starch that has been chemically and/or mechanically processed to rupture all or part of the starch granules.
  • It has better flow compared to unmodified starch.
  • It also shows high compressibility as the aggregated granules undergo plastic deformation on compression.
  • It also possesses disintegrant activity.
  • For good flow, it requires a flow promoter.
  • It is prone to softening when combined with large amounts of magnesium stearate.
  • Trade name : Starch 1500 LM,Prejel; Sepistab ST200; Spress B820