Early detection of opioid-induced constipation in patients initiating weak opioids for chronic non-cancer pain

This post hoc analysis of a Japanese cohort study aimed to identify factors that could assist in early prediction of opioid-induced constipation (OIC). The onset of OIC and the predictive accuracy (sensitivity, specificity, likelihood ratios, and positive predictive values) of early constipation symptoms for OIC onset were assessed within 6 days of weak opioid initiation. Of 63 patients (≥ 18 years) without prior constipation who initiated weak opioids for chronic musculoskeletal pain, 23.8% of them met the Rome IV diagnostic criteria for OIC onset after 3 days. Straining (34.9%), incomplete evacuation (25.4%), and lumpy/hard stools (15.9%) were the common symptoms, with the highest positive likelihood ratio of 2.4 for lumpy/hard stools. Decreased defecation frequency is commonly used for the diagnosis of OIC; however, it was reported in only 1.6% of patients at day 3. The positive predictive value of developing OIC by day 14, based on the early symptoms at day 3, was 70.0% for lumpy/hard stools, 59.1% for straining, 56.3% for sensation of incomplete evacuation, and 72.7% for self-awareness of constipation. Early observation of symptoms such as lumpy/hard stools and self-awareness of constipation could be useful for early prediction of the risk of developing OIC after initiation of weak opioids.