Starch (Amylum)
The mechanism of action of starch is wicking and restoration of deformed starch particles on contact with aqueous fluid and in doing so release of certain amount of stress which is responsible for disruption of hydrogen bonding formed during compression.

The conditions best suited for rapid tablet disintegration are sufficient number of starch agglomerates, low compressive pressure and the presence of water. The concentration of starch used is also very crucial part. If it is below the optimum concentration then there are insufficient channels for capillary action and if it is above optimum concentration then it will be difficult to compress the tablet.

Pregelatinized starch (Starch 1500)
Pregelatinized starch is produced by the hydrolyzing and rupturing of the starch grain. It is a directly compressible disintegrants and its optimum concentration is 5-10%. The main mechanism of action of Pregelatinized starch is through swelling.

Modified starch - Sodium starch glycolate (primogel, explotab)
To have a high swelling properties and faster disintegration, starch is modified by carboxy methylation followed by cross linking. Mechanism of action of this modified starches are rapid and extensive swelling with minimum gelling. Optimum concentration is 4-6 %. If it goes beyond its limit, then it produces viscous and gelatinous mass which increases the disintegration time by resisting the breakup of tablet. They are highly efficient at low concentration because of their greater swelling capacity.

Cellulose and its derivatives
Sodium carboxy methylcellulose (NaCMC and carmellose sodium) has highly hydrophilic
structure and is soluble in water. But when it is modified by internally crosslinking we get modified crosslinked cellulose i.e. Crosscarmellose sodium which is nearly water insoluble due to cross linking. It rapidly swells to 4-8 times its original volume when it comes in contact with water.

Microcrystalline cellulose (MCC)
MCC is insoluble and act by wicking action. The moisture breaks the hydrogen bonding between adjacent bundles of MCC. It also serves as an excellent binder and has a tendency to develop static charges in the presence of excessive moisture content. Therefore, sometimes it causes separation in granulation. This can be partially overcome by drying the cellulose to remove the moisture.

Alginates (alginic acid and Na-alginate)
Alginates are hydrophilic colloidal substances which has high sorption capacity. Alginic acid is insoluble in water, slightly acidic in reaction.It should be used in only acidic or neutral granulation. Alginates do not retard flow and can be successfully used with ascorbic acid, multivitamin formulations and acid salts of organic bases.

Ion-exchange resin
Ion exchange resin (Ambrelite IPR-88) has highest water uptake capacity than other disintegrating. It has tendency to adsorb certain drugs.

Miscellaneous
This miscellaneous category includes disintegrants like surfactants, gas producing disintegrants and hydrous aluminium silicate. Gas producing disintegrating agents is used in soluble tablet, dispersible tablet and effervescent tablet.

Polyplasdone XL and Polyplasdone XL10 act by wicking, swelling and possibly some deformation recovery. Polyplasdone®XL do not reduce tablet hardness, provide rapid disintegration and improved dissolution. Polyplasdone® as disintegrating agent has small particle size distribution that impart a smooth mouth feel to dissolve quickly.


List of Disintegrants

DISINTEGRANTS CONCENTRATION
IN GRANULES
(%W/W)
SPECIAL COMMENTS
Starch 5-20 Higher amount is required, poorly compressible
Starch 15005-15-
Avicel®(PH 101, PH 102)10-20 Lubricant properties and directly compressible
Solka floc® 5-15 Purified wood cellulose
Alginic acid1-5 Acts by swelling
Na alginate2.5-10Acts by swelling
Explotab®2-8 Sodium Starch Glycolate, superdisintegrant.
Polyplasdone®(XL)0.5-5 Crosslinked PVP
Amberlite® (IPR 88)0.5-5 Ion exchange resin
Methyl cellulose, Na CMC,
HPMC
5-10

-
AC-Di-Sol®1-3
2-4
Direct compression
 Wet granulation
Carbon dioxide- Created insitu in effervescent tablet

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