Management of Opioid-Induced Constipation

Prescription opioids are potent pain-relieving medications that, when used correctly, can effectively control pain and increase quality of life for patients with acute or chronic pain. However, optimal pain relief can be difficult to achieve due to the numerous adverse effects (AEs) of opioids, the most common of which are gastrointestinal.^1,2 Most patients on opioids experience one if not more of the AEs during the course of therapy¹ (Table 1). Constipation or opioid-induced constipation (OIC) is by far the most prevalent and persistent AE, with some estimates being as high as 40% in patients receiving opioids.^1-4 Failure to prevent, recognize, or treat OIC can pose challenges in achieving pain therapy goals. Consequently, patients suffer a decreased quality of life, an unwarranted increase in health care costs, and, ultimately, discontinuation or unnecessary alteration of therapy.^1,3,4 As one of the most readily accessible health care professionals, pharmacists are in a prime position to properly counsel patients on their medication use, the AEs, and effective prevention techniques.

Opioid analgesics (Table 2) act on specific receptors found in various places in the body, primarily in the central nervous system. These receptors not only control the pain relief mediated by these medications but also mediate the AEs associated with constipation.² Mu receptors or mu-opioid receptors within the gastrointestinal (GI) tract are what readily cause OIC to develop in patients.¹ When the mu receptor is activated, the coordinated rhythmic contractions required for intestinal motility and mucosal secretions are greatly decreased. This decrease in peristalsis, combined with reduced secretions in the gut and increased reabsorption of fluid from the gut, contributes to the formation of dry, hard stools that are difficult to expel. Patients with OIC usually present with complaints of hard stools, straining, and abdominal distension. Patients may complain of nausea and vomiting that may be treated with an antiemetic or anticholinergic, which may further irritate a patient’s condition.

Treatment options for OIC may be as simple as dietary alterations or as complicated as a bowel management program involving several medications to manage this debilitating and sometimes harmful AE. Lifestyle changes or nonpharmacologic intervention for prevention of OIC are typically recommended when opioid-centered treatment is initiated.^1,4 Although simple lifestyle changes are unlikely to completely prevent OIC,¹ these changes can be extremely beneficial, depending on how a patient initially reacted to a prescribed opioid and on the severity of the AEs. The recommended precautions patients should take are increased: dietary fiber, fluid intake, exercise, and physical activity. Lifestyle changes may not always be suitable for patients, or the changes may be ineffective. In these instances, pharmacists should be involved in recommending pharmacologic therapy.

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