Sodium metabisulphite or sodium pyrosulphite is an inorganic compound of chemical formula Na2S2O5. The substance is sometimes referred to as disodium metabisulfite. Sodium and potassium metabisulfite have many major and nice uses. It is widely used for preserving food and beverages. Sodium metabisulfite is added as an excipient to medications which contain adrenaline (epinephrine), in order to prevent the oxidation of adrenaline. For example, it is added to combination drug formulations which contain a local anaesthetic and adrenaline, and to the formulation in epinephrine autoinjectors, such as the EpiPen. This lengthens the shelf life of the formulation, although the sodium metabisulphite reacts with adrenaline, causing it to degrade and form epinephrine sulphonate.