NSAIDs work by reducing the production of prostaglandins, chemicals that cause pain, fever and inflammation. NSAIDs block the enzyme that makes prostaglandins (cyclooxygenase), resulting in lower production of prostaglandins. As a consequence, inflammation, pain and fever are reduced.
Medical Definition of BILIRUBIN. : a reddish yellow pigment C33H36N4O6 that occurs especially in bile and blood and causes jaundice if accumulated in excess.
Bilirubin is a yellow pigment that causes jaundice and dark yellow colored urine when present in increased amounts. Some people normally have higher bilirubin in their blood. This is known as Gilbert's disease. So their urine will naturally have more bilirubin.