Lactose is a commonly used excipient and is generally used as a diluent or filler for tablets and capsules and in dry powder inhalational products.
Lactose is a naturally existing simple carbohydrate or sugar found in the milk of mammals. It is also referred to as Milk sugar. Commercially lactose is attained from the milk of cows as a by-product of the dairy industry.
Numerous lactose grades are available that have different physical properties such as particle size distribution and flow properties.
In the solid state, lactose appears in various forms i.e.Â
Lactose Monohydrate (alpha)
Lactose Anhydrous. (beta)
Lactose Monohydrate
The most familiar form of lactose used in pharmaceutical products is crystalline a-lactose monohydrate.
 This is available in two forms one is milled and other is sifted.Theses pharmaceutical grades differ in physical properties such as flow, bulk density and particle size distribution. The milled form is used as filler in the production of tablets by the wet granulation and it is also used as a tablet binder.
Lactose Anhydrous
It exists as white to off white crystalline particles or powder.
It is utilized as a tablet, capsule diluent and binder and for Direct compression. Lactose anhydrous is used for moisture-sensitive products due to low moisture level. It is also used in intravenous injections.
 Lactose anhydrous has 70-80% Beta lactose anhydrous and 20_30% Alpha lactose anhydrous.
The coarse grade is utilized when the flow is important for example as diluents in capsule and sachet filling and as a flow improver.
Anhydrous lactose for direct compression is usually manufactured by drying a lactose solution on the surface of a heated drum.
Inhalational Lactose/Respitose
it is utilized as the diluent and dry powder inhaler carrier.
Storage
In lactose, mould growth occurs in moist climates above 80% RH brown colouration may occur in warm and dump condition so store it in a cool and dry place. At temperature 80°c and 80% RH tablet having Anhydrous lactose expand 1.2 times after one day.
Properties of Lactose as Excipient
- Cost-effectiveness
- Easy availability
- Compatibility with active ingredients and other excipients.
- Excellent physical and chemical stability.
- Water solubility.