Conventional Compressed, Film Coated Tablet Formulation Development

In addition to the active ingredient, tablet normally consist of the following excipients.

•     Diluent / Filler
•     Binder
•     Disintegrant
•     Lubricnt
•     Glidant

There must be a harmony between the concentrations of these excipients to manufacture a tablet that comply with the quality parameters.

Given below is a suitable range for the quantity of these materials that I determined by my own experience.

Binder .......................... 3 - 5%

Disintegrant ................. Double than the quantity of the binder

Lubricant + Glidant ….... Not more than 1% of the total weight

Diluent ......................... To make up the required weight

*Note: This range of quantities is not applicable for every tablet formulation.

In order to develop a smooth compact table, a 20-30% portion of the formulation is sieved (normally through sieve no.40) into a fine powder. eventual mixing of this fine powder with the granules result into filling of the of void spaces that develop between the granules and result into a smooth surface of the tablet.
In the conventional wet and dry granulation methods, all the ingredients, except the lubricant and the glidant, are sieved and mixed before the preparation of granules. In the wet granulation method a liquid solution of the binding agent is applied while in the dry granulation, rotary compaction or slugging is normally utilized for the preparation of the grains.

After granulation, the glidants and lubricants are sieved and mixed with the grains. Finally the grains are subjected to the compression.

It is advisable to divide the disintegrant into two halves. One portion is integrated within the granules before granulation while the other is added after the granulation before the compression of the tablets. As a result the disintegrant not only break the tablet but also force the disintegration of the grains.

*Note: For information about the troubleshooting of the common issues that are encountered during compression read the following posts.

http://pharmamend.blogspot.com/2016/09/troubleshooting-for-hardness-friability.html

http://pharmamend.blogspot.com/2016/09/effect-of-particle-size-uniformity-and.html

Film coating of the tablet normally consist of the following excipients.

• Polymer
• Plasticizer
• Polishing agent
• Opaquant
• Colorant
• Solvent
• Miscellaneous: Flavors, antioxidants, antimicrobials etc.

The coating usually constitute 3-4% of the tablet weight. Therefore, the coating formulation is adjusted in such a way that all the ingredients of the formulation, collectively make up the weight that is equivalent to 3-4% of the total tablet weight.

For example, lets say we are supposed to coat a batch of 50 Kg. We calculate 4% of the batch i.e 

50 x 4% = 2 Kg. Therefore, the solid mass of the coating formulation must not be greater than 2 Kg.

Based on my experience the following quantities of the coating agents has proved to be suitable in most of the cases.

Polymer……………….approx. 50%

Plasticizer……………. half the concentration of the polymer

Polishing agent……. 1%

Opaquant..................... 1%
Colorant………………. 1%
Miscellaneous........... Rest of the formulation

*Note: These quantities are not suitable for all formulation. An adjustment in these quantities is made based on the outcome of the results.

In our present case, as the total solid content of the coating formulation is 2 Kg, we can calculate the individual quantities of the excipients as given below.

Polymer………………. 2 Kg x 50% = 1 Kg

Plasticizer……………. 2 Kg x 25% = 0.5 Kg

Polishing agent……. 2 Kg x 1% = 0.02 Kg

Opaquant..................... 2 Kg x 1% = 0.02 Kg
Colorant………………. 2 Kg x 1% = 0.02 Kg
Miscellaneous........... 2 Kg x 22% = 0.44 Kg
                                           Total = 2 Kg

The quantity of the solvent depends on the choice of the solvent. If an organic solvent is utilized in the formulation, normally a 5% coating solution is formed. In case of an aqueous solution, normally 10-15% solution is used.

Lets say we have to prepare a 12% aqueous coating solution for 2 Kg of the solid coating material.
In order to prepare a 12% coating solution,

2000 X 100 ÷ 12 = approx. 16 Liters

So, 2 Kg of the solid content, dissolved in 16 Liters of water, will give a 12% coating solution.