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Books About Tabletting:

Pharmaceutical Powder Compaction Technology

Tabletting Specification Manual 5th Edition (January 2000)

Pharmaceutical Principles of Solid Dosage Forms

Pharmaceutical Technology: Tabletting Technology (Compression)


1.  A tablet is a combination of ingredients that is compressed into a solid mass. The basic components of an immediate release pharmaceutical tablet are:
active drug substance
diluent or filler (see compression aids)

Optional excipients include:

anti-static agent
surfactant (wetting agent)


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2.  Types of Tablets: 

Tablets have the ability to be produced with many different properties including immediate, delayed or sustained release of active drug substance. They can be single or multiple compression (double or triple layered, tablet within a tablet). They can also be coated with an active drug substance, film or sugar coating.

3.  Tablet Properties: 

Physically Acceptable and Stable - tablet print or imprint must be legible, and tablets must be free from chips, cracks, contamination, uneven coloration, etc. Tablets must remain whole during manufacture, coating, packaging, transport and dispensing. In-process controls include:

Tablet Weight Limits on tablet weight are generally set as 3 to 5% of a formulation specific target weight

Some issues that may cause weight variation are powder flow problems, improper die fill, and powder size distribution 

Tablet Hardness Expresses as load required to crush a tablet on end. Measured using a tablet hardness tester. 

Generally, the larger the tablet, the higher the hardness. Smaller tablets (1/4" round) usually have a hardness <5 kp. Larger tablets usually have a hardness <20 kp. 

Some issues that may cause variations in tablet hardness are inconsistent tablet weight, particle size variations, poor powder compressibility, insufficient binder level  

Tablet Thickness Uniform compression force and volume of die fill, leads to uniform thickness
Disintegration Time The time it takes for the tablet to break up into individual granules or particles.

Poor disintegration can come from tablets which are compressed too hard, insufficient disintegrant levels, or too much binder. 

Friability Friability is the tendency of a tablet to crumble, chip or break.

It is measured by tablet weight loss after rotation on a friabilator (i.e. 100 revolutions or 4 minutes at 25 RPM). Typically % loss is <0.5%, but can be up to 2% for very large tablets.

Friable tablets can be caused by low moisture content, insufficient binder, tablet configuration (e.g. sharp versus beveled edges). 

Chemically Acceptable and Stable -  the amount of active drug substance specified on the label must be present in the tablet at the time of manufacture and beyond the expiration date. Tablets must have acceptable drug content uniformity. Tablet must have acceptable drug release characteristics (dissolution). Finished Product Testing Includes:

Identification Used to verifiy that active drug substance in the tablet is correct
Potency A measure of the amount of active drug substance in the tablet (i.e. mg/tablet or % label claim)

Typically in the range of 90 or 95% to 105 or 110%

Related Substances Verifies the quantities of other substances in the product. Limits should be set for other known sustances. Unknown substances should fall within ICH guidelines.
Content Uniformity A measure of the consistency of tablet potency, based on the individual analysis of 10 tablets. Typically 85-115% of label claim with a relative standard deviation of <6%. 
Dissolution A measure of the rate and extent of active drug substance going into solution.

Dissolution specifications vary depending on the type of tablet made.

Typically performed using USP apparatus I (rotating basket) or II (paddle), but may also be done with Apparatus III (Bio-dis) or IV (Flow through cell)


Suppliers of Tablet Presses:

DT Industries Stokes

Fette America,Inc.

Key International


Suppliers of Tablet Tooling:




Contract Tabletting Services  

Norwich Pharmaceuticals


Tablet Formulation Consulting Services

Emerson Resources



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Pformulate 01/02/03