Disintegrant is an excipient which is added to a tablet or capsule blend to aid in the break up of the compacted mass when it is put into a fluid environment. This is especially important for immediate release products where rapid release of drug substance is required.Disintegrant can be used with products that are wet granulated, dry granulated and direct compression. In wet granulation formulations, the disintegrant is normally effective when incorporated into the granule (intragranularly). It may be more effective if added 50% intragranularly, and 50% extra-granularly.

The simplest way to achieve quick disintegration is to use a superdisintegrant in concert with suitable diluents. Superdisintegrants such as croscarmellose sodium, crospovidone, and sodium starch glycolate are frequently used in tablet formulations to improve the rate and extent of tablet disintegration and thereby increase the rate of drug dissolution.

There are three major mechanisms and factors affecting tablet disintegration as follows:
A: Swelling:
Although not all effective disintegrants swell in contact with water, swelling is believed to be a mechanism in which certain disintegrating agents (such as starch) impart the disintegrating effect. By swelling in contact with water, the adhesiveness of other ingredients in a tablet is overcome causing the tablet to fall apart.

B: Porosity and Capillary Action (Wicking):
Effective disintegrants that do not swell are believed to impart their disintegrating action through porosity and capillary action. Tablet porosity provides pathways for the penetration of fluid into tablets. The disintegrant particles (with low cohesiveness & compressibility) themselves act to enhance porosity and provide these pathways into the tablet. Liquid is drawn up or “wicked” into these pathways through capillary action and rupture the interparticulate bonds causing the tablet to break apart.

C: Deformation:
Starch grains are generally thought to be “elastic” in nature meaning that grains that are deformed under pressure will return to their original shape when that pressure is removed. But, with the compression forces involved in tableting, these grains are believed to be deformed more permanently and are said to be “energy rich” with this energy being released upon exposure to water. In other words, the ability for starch to swell is higher in “energy rich” starch grains than it is for starch grains that have not been deformed under pressure.
It is believed that no single mechanism is responsible for the action of most disintegrants. But rather, it is more likely the result of inter-relationships between these major mechanisms.

Disintegrants
  1. Croscarmellose Sodium (Explotab, Primogel) : High swelling capacity with minimal gelling, effective at low concentrations ( 2.0% - 6.0%). Above 8%, disintegration times may actually increase due to gelling and its subsequent viscosity producing effects.
  2. Crospovidone (Polyplasdone XL, Kollidon CL) : water insoluble and strongly hydrophilic. Rapidly disperses and swells in water, but does not gel even after prolonged exposure. Greatest rate of swelling compared to other disintegrants. Greater surface area to volume ratio than other disintegrants. Recommended concentration: 1 to 3%. Available in micronized grades if needed to improve uniform dispersion in the powder blend. Sometimes, the surface of tablet after compression will be look “pimpled”, especially in wet granulation.
  3. L-HPC (Low-substituted hydroxypropyl cellulose) : Insoluble in water. Rapidly swells in water. Grades LH-11 and LH-21 exhibit the greatest degree of swelling. Certain grades can also provide some binding properties while retaining disintegration capacity. Recommended concentration 1-5%. Sodium Starch Glycolate Absorbs water rapidly, resulting in swelling which leads to rapid disintegration of tablets and granules. Recommended concentration: 1.0 – 4.0% but may need to use up to 6.0%. Gels on prolonged exposure to water. High concentrations may cause gelling and loss of disintegration
  4. Modified Cellulose- Internally cross-linked form of Sodium carboxymethyl cellulose. (Accelerates Dissolution), Nymcel.Wicking due to fibrous structure, swelling with minimal gelling. Effective Concentrations: 1-3% (Direct Compression), 2-4% (Wet Granulation)
ADVANTAGES:
  • Effective in lower concentrations than starch
  • Less effect on compressibility and flow ability
  • More effective intragranularly

DISADVANTAGES:
  • More hygroscopic (may be a problem with moisture sensitive drugs)
  • Some are anionic and may cause some slight in-vitro binding with cationic drugs (not a problem in-vivo.)
Working Through Disintegrant
The tablets of crospovidone exhibit significantly higher hardness than do those of croscarmellose sodium. Croscarmellose sodium aids in the disintegration and dissolution of pharmaceutical tablets, capsules, and granules. Coprocessing has been extensively examined for diluents.

Croscarmellose sodium and crospovidone were selected in the present investigation since crospovidone acts by wicking action and croscarmellose sodium acts mainly by swelling action. Therefore, the superdisintegrants complement each other, accelerating the disintegration process when used together. The water uptake by the tablet is facilitated by the wicking action of crospovidone, while the tablet disintegration is facilitated by the swelling force exhibited by croscarmellose sodium.