The use of opioids is becoming more frequent in the general population, due to the increase in chronic pathologies that result in chronic pain. Long-term consumption of opioids due to cancer-related pain or non-tumor chronic pain has been associated with a variety of adverse effects on the gastrointestinal tract. Their effects take place mainly on the enteric nervous system, through receptors in the myenteric and submucosal plexuses. There are 3 recognized main opium receptors (mu, kappa and delta) that are expressed in the central and enteric nervous systems, which mediate the gastrointestinal effects. Opioid-induced bowel dysfunction is a widely known adverse effect, with constipation being the most common manifestation, due to the greater understanding of opium-receptor physiology in the colon. However, their effect on esophageal motility is less known.

Retrospective studies1, 2, 3, 4, 5 have suggested that long-term use of opioids can cause esophageal motility dysfunction, such as achalasia and functional esophagogastric junction (EGJ) outflow obstruction.

Various studies with healthy volunteers have shown increased baseline lower esophageal sphincter (LES) pressure with incomplete relaxation when administering opioids. Kraichely et al.,2 confirmed these findings in clinical practice in a retrospective study of 15 patients with dysphagia and opioid consumption when a manometry was performed. Based on these studies, a recent clinical entity known as opioid-induced esophageal dysfunction (OIED) has been postulated.

The mechanism responsible for the effects of opioids on esophageal motility remains unclear; however, the nitric oxide pathway has been suggested to play an important role.

A retrospective article has recently been published,6 describing a 32% prevalence of OIED in chronic active opioid users. Neither the incidence of OIED nor the profile of patients who may be more frequently affected is known. The study was designed to prospectively evaluate the incidence of esophageal symptoms in patients under chronic treatment with opioids and to define the esophageal motility disorders associated with the use of these drugs.