Review document of the Spanish Association of Neurogastroenterology and Motility on the management of opioid-induced constipation.

Opioid-induced constipation (OIC) is a rising problem due to the progressive increase in opioid prescription. In contrast to functional constipation, opioid-induced constipation is not a functional gut disorder but a side effect of opioid use. Opioids produce constipation due to a decrease in gastrointestinal motility and a reduction in gastrointestinal secretions. The treatment of OIC focuses on three basic pillars: optimizing opioid drug indication, preventing constipation onset, and treating constipation should it develop. As with any other cause of constipation, lifestyle adjustments and laxatives should be the first-line option in the pharmacological management of OIC. Osmotic laxatives such as polyethylene glycol (PEG) are the agents of choice. PEG is inert and is neither fermented nor absorbed in the gastrointestinal tract. Furthermore, it has broad clinical applicability due to its favourable safety profile. If first-line treatments fail, peripheral μ-opioid receptor antagonists (PAMORA) are the drugs of choice. They reduce the peripheral effects of OIC with a minimal potential to diminish analgesia or induce a centrally mediated withdrawal syndrome. Different PAMORA are available in the market both for oral and subcutaneous administration, with demonstrated efficacy for the management of OIC in different clinical trials.