Opioid induced constipation: mechanisms and management

Opioid-induced constipation (OIC), a prevalent form of opioid-induced bowel dysfunction, significantly affects patients with chronic pain, both with and without cancer, who rely on opioid analgesics. OIC reduces opioid effectiveness, impairs quality of life and is frequently underdiagnosed and inadequately managed. A comprehensive literature search of MEDLINE and EMBASE (2000-April 2025) was conducted using terms such as opioid-induced constipation, epidemiology, pathophysiology, treatment, and guidelines. Relevant studies, meta-analyses, and consensus statements were analysed to synthesize mechanistic insights and practical recommendations. This review clarifies OIC's pathophysiology, clinical evaluation, and evidence-based management strategies to guide practicing clinicians. OIC arises from opioids binding to mu-opioid receptors in the gastrointestinal tract, leading to slowed intestinal motility, reduced mucosal secretions, and increased sphincter tone, which collectively cause constipation and related symptoms. Clinicians should proactively educate patients about OIC risks at the start of opioid therapy or during dose escalation. Initial management includes prescribing over-the-counter laxatives, such as stimulant or osmotic agents, tailored to patient needs and tolerances. Regular follow-up, utilizing validated tools like the Bowel Function Index, is crucial to monitor symptom severity and adjust therapies as needed. If initial treatments fail, peripherally acting mu-opioid receptor antagonists are effective second-line options, yet they remain underutilized due to access barriers and low clinician awareness. Unlike prior reviews that primarily address pharmacologic mechanisms, this review integrates mechanistic insights with pragmatic clinical guidance, emphasizing evidence-based implementation strategies and global prescribing disparities to enhance real-world management of OIC.