Although opioids are extremely effective pain relievers, they frequently cause an undesirable side effect – constipation. They affect the gastrointestinal tract in several ways:
- Opioids make stools take longer to move through the gastric system
- They raise non-propulsive contractions in the middle of the small intestine (jejunum) and reduce longitudinal propulsive peristalsis – motions crucial for the movement of food through the intestines – resulting in food that fails to travel through the digestive tract.
- Opioids can partially paralyze the stomach (gastroparesis) so that food remains in the digestive system for longer.
- Opioids reduce digestive secretions and lower the urge to defecate.