Lactose (also referred to as milk sugar) is a sugar which is found most notably in milk. Lactose makes up around 2-8% of milk by weight.Lactose is a disaccharide that consists of ?-D-galactose and ?-D-glucose molecules bonded through a ?1-4 glycosidic linkage.To digest it in milk an enzyme called lactase is secreted by the intestinal villi, and this enzyme cleaves the molecule into its two subunits glucose and galactose for absorption.Lactose is one of the most widely used excipients in the pharmaceutical industry. There are many reasons for it's popularity, such as the fact that lactose is inert (no tendency to react with other ingredients), relatively inexpensive, non-toxic and lactose has a long history of being applied in thousands of successful formulations world-wide. These successful formulations include Dry Powder inhalers, Tablets, Capsules and Sachets