These tablets are meant to be swallowed intact along with a sufficient quantity of potable water, except for chewable tablet. Tablet in this category is the most popular world wide and the major attention of the researcher is towards this direction.

Standard Compressed Tablets
These are the standard uncoated tablets, can be made by some methods :
  • direct compression
  • wet granulation
  • dry granulation
  • double compaction.

They may be used for local action in gastro-intestinal tract or systemic action. When the tablet exert local action, they are formulated as more water insoluble by means of selecting slow dissolving excipients and thus provides local action for long time period, for example antacids and adsorbents.

The drugs that produce systemic action have some aqueous solubility and designed to disintegrate and dissolve quickly so that the drug can be quickly absorbed and produce systemic action.

Multiple Compressed Tablets
The tablets in this category are prepared for two reasons:
  • to separate physically or chemically incompatible ingredients
  • to produce repeat action/ prolonged action tablet. 
There are three categories under this class:
  1. Layered tablets – two to three component system.
  2. Compression coated tablets – tablet within a tablet.
  3. Inlay tablet – coat partially surrounding the core.

I. Multilayered tablets

There are lots of active pharmaceutical ingredients administered simultaneously for patient, but those API are incompatible. Multilayered tablet become the best solution to overcome this problem. It consists of several different granulations that are compressed to form a single tablet composed of two or more layers and usually each layer is of different colour to produce a distinctive looking tablet.

Each layer is fed from separate feed frame with individual weight control. Dust extraction is essential during compression to avoid contamination. Therefore, each layer undergoes light compression as each component is laid down. This avoids granules intermixing if the machine vibrates.

II. Compression coated tablets
This type of tablet has two parts, internal core and surrounding coat. The core is small porous tablet and prepared on one turret. For preparing final tablet, a bigger die cavity in another turret is used in which first the coat material is filled to half and then core tablet is mechanically transferred, again the remaining space is filled with coat material and finally compression force is applied.
To avoid immediate release of both the layers, the core tablet is coated with enteric polymer so that it will not release the drug in stomach while, the first dose is added in outer sugar coating.

Read more :Compression Coating Tablet Manufacturing Method 

III. Inlay tablets
Inlay tablets are a type of layered tablet in which instead of the core tablet being completely surrounded by coating, top surface is completely exposed. While preparation, only the bottom of the die cavity is filled with coating material and core is placed upon it. When compression force is applied, some coating material is displaced to form the sides and compress the whole tablet. It has some advantages over compression coated tablets:
  1. Less coating material is required.
  2. Core is visible, so coreless tablets can be easily detected.
  3. Reduction in coating forms a thinner tablet and thus freedom from capping of top coating.

Atoz is offering Inlay tablets with combinations like Metformin 500 mg sustained release (Outer coat) and Pioglitazone 15 mg (core tablet) which has a very unique advantage.

Read more:

Oral Tablets for Ingestion (Part II)
Oral Tablets for Ingestion (Part III)