Binder is a chemical substance with an adhesive property. They bind the excipients and drug together to provide the mechanical strength. They help to form intergranular bonds. The binder may fuse together locally and form binder bridges between granule surfaces which cohere the granules to each other. Such bridges may be the result of a softening or melting of binder layers during the compression phase.
However, the different type of adsorption bonds may be active between granule surfaces. They may be subdivided into three types:
- Binder-binder
- Binder-substrate
- Substrate-substrate bonds
Binder can be added to the powder in different ways:
- As a dry powder which is mixed with the other ingredients before wet agglomeration. During the agglomeration procedure, the binder might thus dissolve partly or completely in the agglomeration liquid.
- As a solution which is used as agglomeration liquid during wet agglomeration. The binder s here often referred to as a solution binder.
- As a dry powder which is mixed with the other ingredient before compaction (slugging or tableting). The binder is here often referred to as a dry binder.
Both solution binders and dry binders are included in the formulation at relatively low concentration, typically 2-10% by weight. Common traditional solution binders are starch, sucrose and gelatin. More commonly used binder today, with improved adhesive properties, are polymers such as polyvinylpyrrolidone and cellulose derivatives. Important examples of dry binders are microcrystalline cellulose and cross-linked polyvinylpyrrolidone.
Solution binders are generally considered the most effective and this is, therefore, the most common way of incorporating a binder into granules; the granule thus formed are often referred to as binder-substrate granules.
The most important means of controlling the compatibility of granules has been to add a binder to the powder to be granulated. This is normally done adding the binder in a dissolved form, thereby creating binder-substrate granules. An increasing amount of binder can correspond to increase compatibility but this is not a general rule. It is because on increasing the binder concentration, dissolution and disintegration rate would decrease due to the higher cohesive force between the granules. So they are generally used in a smaller amount.
Recommended binder concentration:
Sr.No
|
Binder
|
Recommended %
|
1
|
Acacia gum with water or hydro alcohol
|
2 to 5 %
|
2
|
Gum tragacanth with water
|
1 to 3 %
|
3
|
Gelatin with water
|
1 to 4 %
|
4
|
Sucrose with water
|
2 to 20 %
|
5
|
Starch paste in water
|
1 to 4 %
|
6
|
Sodium alginate with water
|
3 to 5 %
|
7
|
Methyl cellulose with water
|
2 to 6 %
|
8
|
Sodium carboxymethyl cellulose with water
|
6 %
|
9
|
Ethyl cellulose with alcohol
|
0.5 to 2 %
|
10
|
Hydroxy propyl methyl cellulose with water, hydro alcohol, methylene chloride etc.
|
2 to 5 %
|
11
|
Polyvinyl pyrrolidone with water, alcohol and hydro alcohol
|
0.5 to 5 %
|
12
|
Magnesium aluminum silicates with water
|
2 to 10 %
|
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