Binders are the most important excipients used to combine powder particles with each other to form granules in wet granulation.Wet granulation is the most commonly used method of manufacturing granules for tablets and capsules in pharmaceutical industries.
To learn complete wet granulation method read following,
In wet granulation binder can be added in powder premix in the following ways,
- Binder Solution/Suspension
- Dry Powder Activation
- Dry Powder+Binder Solution/Suspension
- Binder Paste
- API In Solvent
- Solvent Alone
Binders used for wet granulation are in solid powder form and are mixed in a suitable solvent either aqueous or organic depending upon the formulation.
Binder in form of Solution/Suspension
is the most commonly and widely used method for binder preparation.
Method Of Preparation
- Take the required amount of binder according to BMR.
- Sieve the binder if required(Varry material to material)
- Measure required quantity of solvent according to BMR.
- Add powder material slowly in solvent using a propeller or homogenizer mixer.
- Mix until a solution or lumps free suspension is prepared.
- It is ready for use and adds it slowly in powder premix in a controlled manner.
- Too fast addition rate may result in localized over-wetting or Case Hardening.
Dry Powder Activation
Dry Powder activation is a method of binder addition in which binder in powder form is mixed in a premix of powder and is activated by the solvent.
Method Of Addition
- Binder quantity is taken according to BMR.
- It is sieved and added in premix(API+Diluent+Disintegrant etc) ready for granulation.
- After uniform mixing of binder material with premix (API+Diluent+Disintegrant etc) add a measured quantity of solvent(water or organic solvent) in the premix.
- This solvent addition activates the binder present in premix and binds powders to form granules. (Chances of case hardening are minimised).
Dry Powder Activation+Binder Solution/Suspension
- It is a combination of the above two methods.
- Sometimes all the binder quantity is not added in solution or suspension form because it may result in a too viscous solution or suspension difficult to pour.
- So to avoid this some quantity is added in solvent and remaining is added in dry form in the premix.
In this method the binder is added in the form of paste.
Common example is Starch paste.
Method Of Preparation
- Simple starch is not soluble in cold water.
- Starch is added in water and mixed.
- It is then heated at a suitable temperature to form a paste.
- Paste formed is then cooled and added in powder premix to form granules.
API In Solvent
- For some formulations, API can be added in suitable solvent depending upon the formulation and is poured or sprinkled over powder premix to form granules.
- It is usually used to improve the uniform distribution of API in the formulation.
In this method, formulation requires no binder.
Only Addition of suitable solvent is sufficient to activate granules formation.