Direct compression (DC) is the most straightforward manufacturing option, with the fewest manufacturing steps, making it the easiest to control and least expensive. The direct compression tablet process uses two primary process steps: blending the API with excipients and compressing the finished tablets. Apart from process simplicity, the key advantages of direct compression vs wet granulation include reduced capital, labor and energy costs for manufacture, and the avoidance of water for granulation for water sensitive drug substances.

Despite involving only a few process steps, product design in the direct compression method for tablets can be challenging because of the numerous competing objectives. Among several requirements, the compression mix has to flow to ensure a consistent tablet weight; it has to compress and compact into robust tablets; and the resulting tablets have to remain stable over time to maintain safety and efficacy.

As evidenced, there are advantages and disadvantages of direct compression method because it’s directly impacted by material properties since these are not altered by granulation process steps. Therefore, it requires increased performance, quality and consistency from starting ingredients, including excipients. The use of poorly controlled or inadequately specified raw materials may lead to several challenges in DC, such as poor flowability, inconsistent tablet weight, unsatisfactory tablet strength, lack of content uniformity or segregation and dissolution failure.

Formulation and process considerations:

1. API dose and final tablet size
2. API particle size and compressibility
3. Binder and diluent particle size and bulk density
4. Powder blend adhesive and cohesive characteristics
5. Powder blend moisture content
6. Powder blend flow and compressibility
7. Type of lubricant and lubrication time
8. Manufacturing train design and segregation potentials 

Diluent, flow and compression aid

Avicel^® PH mechanism and critical material attributes

Avicel^® PH MCC is derived from wood, in which cellulose chains are packed in layers held together by a cross-linking polymer (lignin) and strong hydrogen bonds. Both softwoods (evergreen conifer) and hardwoods (deciduous broadleaf) can be used.

During compression, MCC plastically deforms and therefore maximizes the area of interparticle bonding. The proximity of hydrogen groups on adjacent cellulose molecules enables the formation of numerous hydrogen bonds, which account almost exclusively for the strength and cohesiveness of compacts, even under low compression forces. Mechanical interlocking of irregularly shaped and elongated MCC particles has also been suggested to enhance tabletability. 

*Examples only and not representative of a complete list of recommended products or benefits

Enabling Direct Compression for Controlled Release 

In matrix-controlled release applications, the direct compression method delivers increased productivity and lower manufacturing cost. METHOCEL™ DC2 uses particle engineering to modify particle morphology, resulting in improved powder flow without any additives. METHOCEL™ DC2 offers excellent processability including improved content uniformity and tablet weight consistency at elevated tablet press speed.

We want to help you be successful in whatever application you are considering, so please contact us if you need more assistance. Our experts are eager to tackle your challenges.