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This article is adapted from one that originally appeared in the March 2014 issue of Primary Care Reports.
More than 40% of ED visits are related to pain.1 The Joint Commission has made the assessment and treatment of pain in the ED one of its standards.2 The use of opioid medications has been increasing in both adults and children.3-5 In 2009 there were more than 200 million prescriptions for opioid medications, with enough medication dispensed to supply every adult in the United States with the equivalent of 5 mg of hydrocodone every four hours for one month.4,6
Along with the increase in opioid use has come an increase in misuse and in adverse events. Much has been written and discussed about the problem of drug abuse and overdose. This monograph will not further discuss this topic. It is estimated that in 2009 there were 4.6 million ED visits for drug-related events — 50% of these were for drugs taken as prescribed. Our focus in this article will be the prevention and treatment of the side effects of opioid use.
— Sandra M. Schneider, MD, Editor
Constipation
Constipation is the most common side effect of opioids. The gastrointestinal tract is innervated by the enteric nervous system, with mu, kappa, and delta receptors. The mu-opioid receptors in the submucosal plexus are mainly responsible for constipating effects.7 During times of stress, bodies synthesize endogenous opioids, which suppress intestinal motility. Exogenous opioids also bind to these enteric receptors, inhibiting neurotransmitter release. This decreases peristalsis and mucosal secretions (as well as pancreatic and biliary secretions). Stool remains in the intestines longer, increasing fluid reabsorption and leading to hard stools. There is also a degree of centrally mediated effect, as spinally administered opioids also decrease gastric emptying and increase transit time. Subsequently, patients strain to stool and sometimes have painful defecation. If they have incomplete emptying or avoid stooling due to pain, the situation only worsens. Cramping and bloating often occur.8,9 Unlike most other opioid side effects, tolerance does not generally develop to constipation.
Prevalence estimates for constipation due to opioid use vary widely. They depend on the definitions used. They also vary based on whether assessments are made by chart review or by patient...