"In 2009, 1.2 million emergency department (ED) visits (an increase of 98.4% since 2004) were related to misuse or abuse of pharmaceuticals, compared with 1.0 million ED visits related to use of illicit drugs such as heroin and cocaine (3)."

Source

Centers for Disease Control and Prevention, Vital Signs: Overdoses of Prescription Opioid Pain Relievers — United States, 1999–2008, Morbidity and Mortality Weekly Report, November 4, 2011 / 60(43);1487-1492