List of products in the National Drug Code with proprietary name . Ustekinumab is used to treat plaque psoriasis, a certain type of arthritis (psoriatic arthritis), or certain bowel conditions (Crohn's disease, ulcerative colitis). It works by blocking certain natural proteins in your body (interleukin-12 and interleukin-23) that cause inflammation (swelling) in these conditions. Ustekinumab does not cure these diseases, but helps to lessen symptoms of the disease. It can help to decrease the amount of plaques in plaque psoriasis, decrease the number of swollen/painful joints in psoriatic arthritis, and decrease symptoms such as abdominal pain/cramping and diarrhea in Crohn's disease and ulcerative colitis.