A 32-year-old patient on inflixmab for maintenance therapy of ulcerative colitis (UC) is admited to the hospital with abdominal pain, six bloody stools daily, temperature of 38 ºC, and heart rate of 100 beats per minute. Colonoscopy demonstrates pancolitis with erythema, ulcerations, and scattered pseudopolyps. The best next step in treatment is intravenous (IV)