 The most common adverse effects of treatment with deracoxib are vomiting, anorexia, lethargy and depression.Other adverse effects of deracoxib are caused by its effects on the gastrointestinal tract, and include erosions or ulcerations of the lining of the stomach or intestines.Serious adverse effects, including ulcers which perforate the gastrointestinal tract, have occurred in dogs administered higher than recommended doses of deracoxib, or dogs administered deracoxib at the same time as (or soon after) other NSAIDs or corticosteroid medications.