Binders are one of the most important excipients used in the manufacturing of tablets, capsules, pills, and dry powder suspensions.In broader terms binders or binding agents are used for manufacturing oral solid dosage forms. Binders are the excipients that give cohesiveness to the powders and binders are the materials that are used to convert powders into granules.
Oral solid dosage forms are manufactured by the following methods,
- Wet granulation
- Dry granulation
- Direct Compression
To understand the use of binders, first have a brief look over the need of granulation and granulation methods.
Why Do We Need Granulation?
Granulation is a process in which powders are converted into large agglomerates called granules using binders in dry form or in solution form or by the application of pressure.
- We convert powders into granules to increase compressibility.
- We also use a granulation method to increase flow rate.
- Powders are elastic and may promote capping and lamination so we convert powders into granules to overcome these issues.
- To prevent segregation.
Wet granulation is a process in which we convert powders into granules using powder binder in dry form which is activated later on using solvent or binder in solution form using water or organic solvent.
The wet mass produced in this method is sieved,dried,screened and finally mixed to get the desired granular product.
Limitations Of Wet Granula tion
Wet Granulation method is not used for moisture and heat sensitive sensitive products.
Read Details of wet granulation in following,
Dry granulation method is used for those products which are degraded by heat or moisture.In dry granulation as the name indicates no solvent is used and in this process fine powders are transferred into granules by application of pressure.
Powder Binders in dry form are used in dry granulation to give strength to the granules and tablets.
Direct compression method is used for those products which have good compressibility properties and usually a powder binder like microcrystalline is used to give high compressibility.
Classification Of Binders
Binders or binding agents are classified on following basis
- On Basis Of Origin
- On Basis Of Of Use
1.0 On Basis Of Origin
On basis of origin,Tablet Binders or binding agents are classified into following classes,
- Natural Binders
- Semi Synthetic Binders
- Synthetic Binders
As the name indicate natural binders are obtained from natural sources and main examples of natural binders as follow,
Common examples of gums used as binders as follow,
Starch paste is commonly used as a natural binder.
Sugars like liquid glucose,sucrose are used as natural binders.
Cautions For Natural Binders
Natural binders are a good source of microbial growth.When we use natural binders in our formulations, there are chances of microbial growth.
So whenever natural binders are used, dry the granules properly after kneading.
Antimicrobial preservatives may also be used in formulations containing natural binders.
Semi Synthetic Binders
Following are semisynthetic binding agents which are used in manufacturing of pills, tablets and capsules.
- Hydroxypropyl Methylcellulose (HPMC)
- Hydroxypropyl Cellulose (HPC)
- Ethyl Cellulose (EC)
- Methyl Cellulose (M.C)
- One of most commonly used synthetic binder for manufacturing of tablets and capsules is PVP Or Polyvinyl Pyrolidine also known as Kollidon.
- PVP is available in different grades and it is soluble in both water and IPA.
- Read details of PVP in following,
2.0 On Basis Of Use
On the basis of use of binders there are following types,
- Solution Binders
- Binders Activation
- Dry Powder Binder
- Binders For Direct Compression
Solution binders or tablet solution binders are used for wet granulation.As the name indicates,in solution binders the binder in powder form is added in a suitable solvent to form solution or suspension and this solution of binding agent is poured or sprinkled over the powder pre mix to form large size agglomerates which are then sieved to form granules.
Paste binders are the binders which are used during wet granulation in the form of paste.
To form paste,binder in powder form is added in water and then heat is applied and paste is formed.
- Starch Paste
- Binder activation is a process which is used during wet granulation and in this method binder in powder form is mixed with other ingredients which are required to be granulated.
- Once the powder binding agent is properly mixed it is activated by addition of solvent which results in adhesion of powder particles.
- Dry binders are the type of binders which are used in dry powder form to give strength to the granules and tablets.
- Dry binders are usually used in dry granulation and as the name indicates no solvent is required for use of these binders.
- Microcrystalline Cellulose
Direct Compression Binders
- Direct compression binders are the binding agents which are used for the direct compression process and these binders have good flow properties and high compressibility.
- Avicel PH 102
- Silicified Microcrystalline Cellulose (SMCC)
- Pregelatinized Starch (PGS)
- Direct Compression DBCPD
Method Of Binder Addition
- Read details of binder addition in following,
Characteristics Of A Good Binder
Following are characteristics of a good a good binder,
- It should be compatible with other ingredients of the formulation.
- It should easily be available for commercial use and should be cost effective.
- Binder selected for wet granulation should have good spreading properties meaning it should spread uniformly over powder blend.
- Binder selected for direct compression should have good flow properties.
- Binder selected for direct compression should have good compressibility.
Effects Of Binding Agent On Formulation
Binder selection and concentration of a binding agent is a very critical process and may effect
- Tablet Hardness
- Tablet Friability
- Tablet Disintegration
- Tablet Dissolution
Tablet hardness is directly related to the binder used in the formulation.
Higher concentration of binder results in production of strong granules and as a result high tablet hardness can be achieved.
Lower concentration of binders results in fragile granules and it results in low tablet hardness.
Higher concentration of binder produces strong tablets with no friability and low binder concentration may result in tablet capping,
chipping,lamination and friability.
Higher binder concentration may result in prolonged disintegration time due to strong binding of granules.
Dissolution profile of oral solid dosage forms are decreased due to increased concentration of binding agents,
because drug release is slow due to strong binding.
Bioavailability is directly related to the dissolution profile and as we know dissolution profile decreases with increased concentration of binder so bioavailability is also decreased due to higher concentration of binder used in formulation.
Pill Binders / Pill Binding Agents
Pill are also a solid dosage form and are defined as,
Small round or oval shaped solid unit dosage forms containing drugs,hormones or vitamins etc for oral use are known as pills.
Pills are manufactured by using different types of granulation methods and binders used for pill manufacturing are known as pill binders or pill binding agents.
Nowadays pills are replaced by tablets and capsules, usually birth control pills, are available in the market.
Bulk Ready Mix Tablet Binders
Bulk ready mix tablet binders are the mixture of different ingredients to give better tablet compression due to improved binding properties and better flow properties.
Ready mix tablet binders consist of following,
- Silicified Microcrystalline Cellulose
- Mg Stearate
This ready to use mixture reduces processing time and tablets can easily be compressed by mixing API with this ready to mix combination.
- Classification of Excipients.
- Role of diluents in tablet granulation.
- Role of mannitol in pharmaceutical products.
- Uses of Starch and modified starch in tablet manufacturing.
- Different Grades of Microcrystalline Cellulose or Avicel .
- Role of Lactose in tablet manufacturing.
- Role of Dibasic calcium phosphate in tablet manufacturing.
- End point determination or wet granulation.
- Equipments used for Granulation.
- Working of Rapid Mixing Granulator.