Mixing in Pharmaceutical Industry Full Chapter PDF free download

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Mixing may be defined as a unit operation that aims to randomize two or more components, so that each unit (particle, molecule etc.) of the components lies as nearly as possible in contact with the unit of the other components.

The Importance of mixing

Very few pharmaceutical products contain only one component. Mostly several ingredients are needed. e.g. to produce a tablet dosage form containing a drug which containing active ingredient of 1 mg, other components (e.g. diluents, binders, disintegrants and lubricants) will be needed both to enable the product to be manufactured and for it to be handled by the patient.

Whenever a product contains more than one component a mixing step will be needed in the manufacturing process, in order to ensure an even distribution of the active ingredient, to ensure an even appearance, or to ensure that the dosage form releases the drug at a uniform rate. The unit operation of mixing is therefore involved at some stage in the production of practically every pharmaceutical preparation. This is mentioned below by the list of products that use mixing step.

• Tablets, capsules, sachets and dry powder inhalers - mixtures of solid particles (powder mixing)

• Linctuses, Elixirs, - Mixtures of miscible liquids

• Emulsions and creams - Mixtures of immiscible liquids

• Pastes and suspensions - Mixtures of liquid and solid.

Types of Mixture

•          Positive Mixture

•          Negative Mixture

•          Neutral Mixture

•         Positive mixture

•         Mixing of materials such as gases or miscible liquids.

•          In this case irreversible mixing takes place,

•          Occur by diffusion, without the expenditure of energy.

•         Generally such materials do not present any problems in mixing.

•         Negative Mixtures

•         Mixing that requires energy, and the components of which separate unless work is continuously applied.

•         These are more difficult to be formed and maintained.

      e.g. Mixing of suspension of solids in liquids.

•         Neutral Mixtures

•          These are static in their nature, i.e. the components have no tendency to mix spontaneously nor they segregate.

e.g. Examples of this type of mixture include mixed powders, pastes and ointments.

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