Role of Diluents/Fillers in Pharma

Diluents are also called fillers and are used to increase the bulk weight of tablet or solid dosage form. Diluents have no pharmacological impact but are required for formulation development to give dosage form a proper dimension and weight.

Minimum Tablet size should be above 2-3 mm and weight of tablet should be above 50mg for easy compression and handling.  

if the potency of an API is 5mg then for example after adding other excipients like binders, disintegrants, lubricants and glidents etc the required size of the tablet is not achieved. For example, our target tablet weight is 100mg but after addition of API and all other excipients except Diluent its become 60mg then remaining 40mg is achieved by the addition of Diluent. The diluent may be used up to 80% depending on the formulation.

The diluent used should not interact with API or with other excipients and should not promote microbial growth in the formulation.

Classification of Diluents.

Diluents are classified depending on chemical nature and solubility.

Organic Diluents

  • Lactose
  • Starch 
  • Pre-Gelatinized starch
  • Sucrose
  • Mannitol

Inorganic Diluents

  • Calcium phosphate dibasic
  • Calcium phosphate Tribasic

Water Soluble

  • Lactose 
  • Mannitol
  • Sucrose

Water Insoluble

  • Starch
  • Cellulose
  • Calcium Phosphate
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