Diluents are used in tablet formulation for several reasons, but one of the main reasons for using tablet formulation is to increase the bulk of the tablets. Some that are used as tablet diluents include starch, sucrose, talc, fructose, mannitol (pearlitol ), Microcrystalline cellulose, calcium carbonate, maltodextrin, etc.

Diluents in Tablet Formulation: Diluents or bulking agents or fillers, are the most commonly used words in tablet formulation. so one of the straightforward answers to the use of diluents is to increase the tablet size as such without affecting the therapeutic properties, Diluents are inert materials used in tablet formulation and they do not have any therapeutic benefit. The choice of diluent used must be appropriate as some diluents are associated with decreased bioavailability as you already know use of calcium salt as a diluent in tetracycline antibiotics reduced the bioavailability nearly to less than half of standard antibiotic products. Some diluents have directly compressible properties and are used for direct compression of tablets.

Some Important Uses of Diluents:

• Bulking Agent
• Improve flow properties
• Enhance Compressibility
• Even distribution of API in tablet
• Improve stability
• Adjustment of tablet weight
• Masking Taste

Let us know in brief of some common diluents

lactose is the most commonly used diluent in tablet formulation, it has less interaction with drugs and anhydrous lactose is more advantageous as it does not undergo Millard reaction – it is nothing but discoloration or browning with certain drugs and anhydrous lactose should be taken care while using as it can pick up moisture at high humidity.

Starch is also used as diluent but limited use owing to poor flow and more moisture content in it. Hydrolyzed starches like emdex and cellutab are used and these are directly compressible diluents and free flowing properties.

Microcrystalline cellulose called Avicel used for direct compression, and available as MCC ph101 and ph102

Examples of diluents: maltose, fructose , dextrose, maltodextrin, calcium carbonate, MCC silicified, starch, talc, xylitol etc.