Treatment-emergent AEs occurring more frequently for naloxegol vs. UC were abdominal pain ( 17.8 % vs. 3.3 % ) , diarrhoea ( 12.9 % vs. 5.9 % ) , nausea ( 9.4 % vs. 4.1 % ) , headache ( 9.0 % vs. 4.8 % ) , flatulence ( 6.9 % vs. 1.1 % ) and upper abdominal pain ( 5.1 % vs. 1.1 % ) .