Differences in the morphine-induced inhibition of small and large intestinal transit: Involvement of central and peripheral μ-opioid receptors in mice.

Constipation is the most common side effect of morphine. Morphine acts centrally and on peripheral sites within the enteric nervous system. There are a few comprehensive studies on morphine-induced constipation in the small and large intestine by the activation of central and peripheral μ-opioid receptors.