Each sinus cocktail injection contains 1,000 mcg of B12 and 4mg of dexamethasone. B12 helps to give you a boost of energy and also helps to regulate the nervous system, digestive system, and heart, promoting an overall sense of wellbeing. Dexamethasone is a corticosteroid. The purpose of this medication is to decrease swelling and inflammation- in the case of the sinus cocktail shot it aims to decrease the swelling in your sinuses. This will relieve the common sinus pressure/pain that accompanies sinusitis, and will also allow the mucous to drain from your sinuses.