Mechanism of disintegration|Superdisintegrants

Disintegrants are the class of excipients that are used in tablets or capsules to break the tablet or capsules into small parts or fragments when coming in contact with water or fluid. In technical terms, disintegrants break the tablets into granules and granules into fine powders to release the Active Pharmaceutical ingredient and enhance its bioavailability.Disintegrants improve the dissolution profile of the drugs and different types of disintegrants and Super disintegrants are used in pharmaceutical industries.

       

Disintegrant

Disintegrants are conventional types of excipients and are required in large amounts to disintegrate the tablet.

Example

Following are examples of disintegrants

• Starch
• Microcrystalline Cellulose
• Clays

Starch is usually used as disintegrant at 3-20% Concentration.

Clays are rarely used and are used for colour products because of their appearance .

Super-Disintegrant

Super-Disintegrants, as the name indicates, are superior to conventional disintegrants and are obtained from modification of starch or  cellulose.

Examples

Examples of Super disintegrants are as follow

• Sodium Starch glycolate
• Pregelatinized Starch
• Croscarmellose sodium
• Cross-linked PVP

Super disintegrants are more effective even in small concentrations.

Sodium starch glycolate is used as a super disintegrant in a 2-8% concentration.

Double Disintegration

As we read previously that disintegrants are used to break the tablets so now will discuss the term double disintegration.

• Double disintegration is a phenomenon in which we do not use all quantities of disintegrant or super disintegrant in a single stage during tablet manufacturing.
• We divide disintegrants into two portions, maybe 50,50% or any other ratio depending upon the formulation.
• One portion is used before kneading mean before wetting the power mix and the other portion is used after dry sieving in final blending.
• The portion used before kneading is known as intragranular disintegrant and the portion used after dry sieving in final blending is known as extra granular disintegrant.

Benefits of Double Disintegration

We can use disintegrants or super disintegrant in a single portion as well but here we will discuss what are the benefits of the double disintegration phenomenon.

• When we add disintegrants in two portions it has the advantages of improved disintegration, dissolution and finally the bioavailability.
• The disintegrant added in the extra granular stage breaks the tablet into granules and the disintegrants added into the intergranular stage breaks the granules into a fine powder and releases the drug.
• So disintegration time is reduced, dissolution profile and bioavailability is enhanced.
  

Practical Observation

• Sometimes it is observed that during disintegration tablets are converted into granules in a short period for example in 3 to 4 minutes but the resultant granules take more time to dissolve, usually 9 to 10 minutes.
• One possible reason for this problem is that the disintegrant is usually added in the final blending or a very small portion is added in the intragranular stage.
• Due to this absent or less amount of disintegrant in the intragranular stage,the granules take more time to dissolve or break.

Solution

• Increasing the amount of disintegrant at the intragranular stage usually resolves this problem.

Mechanism of Disintegration

All the excipients used as disintegrant show their function because of the following mechanism

• Swelling
• Wicking
• Release Gases/Effervescent
• Heat Generation
• Strain Recovery

Swelling

• Swelling is the main and basic mechanism by which various disintegrants work.
• In the swelling mechanism particles of disintegrant swell when coming in contact with water.
• Due to swelling, disintegrants exert pressure from the inside to break the tablet.
• In a swelling mechanism particles of disintegrant absorb water and expand like a sponge.
• Due to expansion, the bounds inside the tablet are broken down and the tablet is  converted into fragments to release  the drugs.

Example

Starch-based materials show disintegration by swelling mechanism.

Wicking

• Wicking is also known as capillary action.
• Many disintegrants show their function by wicking in which water is taken or drawn inside the tablet by capillary action and then this initiates tablet breakage.

Example

Cellulose-based materials show disintegration by wicking mechanism.

Effervescent

• Some tablets disintegrate by releasing gases like carbon dioxide and these types of tablets are known as effervescent tablets.
• In effervescent tablet acid like citric and base like sodium carbonate are used to react.
• Due to the reaction, carbon dioxide is released and the tablet disintegrates.

Heat Generation

• Some tablets disintegrate by heat generation mechanism.
• In this method, some materials used in tablets release heat when they come in contact with water.
• This heat results in expansion of the air present in the tablet pores.
• Due to air expansion, the tablet is disintegrated.

Strain Recovery

• Some materials deform on the application of pressure during tablet compression and regain their shape when come in contact with water and results in tablet disintegration.

Also Read:

Classification of Excipients

Factors Affecting Disintegration

Lubricants

Lubricants are added into tablet formulation to prevent sticking and picking.

Lubricants form a covering around granules so if hydrophobic lubricants are used they retard water penetration so disintegration time is prolonged.

Tablet Hardness

Porous tablets result in rapid wicking and swelling action but when the hardness of the tablet is  increased the porosity of the tablet is decreased so disintegration time  is increased with increased tablet hardness.

Effect Of pH 

The function of some disintegrants and superdisintegrants is also affected by the pH of the medium.

For example, the swelling property of sodium starch glycolate is decreased in an acidic environment.

Solubility

• Solubility of API and excipients used in tablets plays an important role in the performance of disintegrants.
• Use of disintegrant and super disintegrant is mainly dependent on the formulation.
• When we use insoluble or slightly soluble API and other excipients like filler and binders in our formulation we should use  a swelling type of disintegrants.

When we use soluble type API and other excipients like filler and binders in our formulation we should use Wicking type of disintegrants.

Disintegrant For Capsules

• The capsules dosage form is different from the tablet dosage form because in capsules drug substance is closed in a shell. 
• The selection of disintegrant for the capsule is very critical.
• For capsules, we should use a swelling type of disintegrant or super disintegrant because when the capsule end is separated from the body the water results in swelling of disintegrant and this swelling pulls or expels the other formulations out of  the capsule shell and results in disintegration.
• If we use Wiking type disintegrant or super disintegrants it results in slow disintegration due to the formation of a diffusion barrier at the capsule end.

Also Read: 

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2. Line Clearance in pharmaceuticals.
3. How to become a skilled pharmacist?
4. Recomended Sound level for working.
5. Role of mannitol in pharmaceutical products.