Decadron 20 mg (Dexamethasone) Injection – Powerful Corticosteroid for Inflammation & Allergy in Pakistan Decadron 20 mg contains dexamethasone, a potent corticosteroid medicine used to control inflammation, suppress immune reactions, and manage severe allergic symptoms. It’s commonly used for conditions such as arthritis, asthma, autoimmune disorders, severe allergies, and supportive roles in oncology care like reducing chemotherapy‑induced nausea and inflammation.