Role of Diluents/Fillers in Pharma

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

The minimum tablet size should be above 2-3 mm and the weight of the 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,glidents etc the required size of the tablet is not achieved. For example, our target tablet weight is 100mg but after the addition of API and all other excipients except Diluent, it becomes 60mg the 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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