Pancreatic insufficiency or intestinal malabsorption may result in reduced or absent digestion of RAVICTI and/or absorption of phenylbutyrate and reduced control of plasma ammonia. Monitor ammonia levels closely in these patients.Most common adverse reactions in ≥ 10% of patients are: diarrhea, flatulence, headache, nausea, vomiting, fatigue, decreased appetite, hyperammonemia, dizziness, headache, upper abdominal (stomach) pain and rash. Corticosteroids, valproic acid, or haloperidol may increase plasma ammonia levels; monitor ammonia levels closely when used concomitantly with RAVICTI. Probenecid may affect renal excretion of metabolites of RAVICTI including PAGN and PAA. The use of RAVICTI in pregnant women may cause fetal harm. Breastfeeding is not recommended during RAVICTI treatment. Please see full Prescribing Information for RAVICTI at www.hyperiontx.com. Conference Call and Webcast Information Hyperion's senior management team will host a conference call on Monday, February 4, 2013 to discuss the FDA approval beginning at 5:30 a.m. PT; 8:30 a.m. ET. To access the live teleconference, please dial 877-847-7188 (U.S.) or 408-427-3787 (International) and reference the conference ID# 96938694. To access the webcast, please go to the Events page on the Investors section of the Company's web site at www.hyperiontx.com. A telephone replay will be available approximately two hours after the call for one week by dialing 855-859-2056 from the (U.S.) or 404-537-3406 for (International) callers and entering reservation number 96938694. A replay of the webcast will be available on the Events page on the Company's web site for 30 days. About Urea Cycle Disorders Urea cycle disorders, or UCDs, are a collection of inherited metabolic disorders in which affected patients suffer from high levels of systemic ammonia, a potent neurotoxin. Ammonia is produced via normal protein ingestion; the body normally detoxifies it by converting it through a series of enzymatic steps to urea, which is excreted in urine. Throughout their lives, UCD patients may experience recurrent hyperammonemic crises in which ammonia levels rise, and can develop complications ranging from nausea, vomiting and headache to coma and death.