DEPO-MEDROL (METHYLPREDNISOLONE ACETATE) or depomedrol is an anti-inflammatory steroid used to treat certain allergies, skin conditions, and types of arthritis. It is a corticosteroid of long duration. Methyl prednisolone acetate: 40 mg Polyethylene glycol: 29 mg Sodium chloride: 8.7 mg Myristil gamma-picolinium chloride: 0.195 mg Sterile water for injection, c.b. 1 ml.