In the development of direct compression (DC) tablet formulations, selecting the right diluent is a critical decision that directly impacts blend flowability, compressibility, tablet strength, disintegration time, and overall manufacturing cost.
Spray dried lactose (SDL) and monohydrate lactose are among the most widely used tablet diluents in DC. SDL, in particular, is preferred due to its superior flow and compaction properties, making it ideal for high-speed compression. The choice between 100 mesh and 200 mesh monohydrate lactose depends on the nature of the active ingredient—200 mesh is better suited for fine particle APIs, while 100 mesh is generally used with more granular actives.
Microcrystalline cellulose (MCC) is another staple in DC formulations, often combined with lactose to improve compressibility and disintegration. Common blending ratios like 30:60, 50:50, or 60:30 of SDL to MCC are used depending on the desired flowability and cost-effectiveness. These combinations allow formulators to tailor blends for specific performance or economic goals.
Apart from lactose and MCC, several advanced DC-grade excipients offer excellent compressibility and stability. Mannitol DC and Lactitol DC (such as Finlac™) are increasingly used, especially for moisture-sensitive APIs. These sugar alcohol-based diluents have low moisture pickup and reduced hygroscopicity, which helps extend the shelf life of formulations. They also produce marginally harder tablets at the same compression force, which can be advantageous in maintaining tablet integrity.
Spray dried lactose, Mannitol DC, and Lactitol DC are typically used in concentrations ranging from 30% to 65% in tablet formulations. Lactose 100 NF and 200 NF are also common, used in the range of 25% to 60%, depending on their mesh size and particle properties.
Ultimately, the selection of a diluent in direct compression is a fine balance—ensuring optimal flow during manufacturing, maintaining tablet performance, enhancing stability, and controlling cost. The right choice not only ensures manufacturing efficiency but also impacts the success of the final dosage form in the market.
Read also:
- GMP Guideline for Pharmaceutical Excipients
- Choice of Excipients and Its Grade in Pharmaceutical Formulation
