Opioid-induced constipation in mixed chronic pain patients: Prevalence and predictors analysis

Objectives: Assessment of opioid-induced constipation (OIC) prevalence and relationship with demographic, clinical, and drug predictors in our daily practice. Design: Observational and retrospective study. Setting: Chronic pain (CP) center of Bologna’s Teaching Hospital, Italy. Subjects: Mixed consecutive CP opioid-user outpatients (n = 128). Main outcome measure(s): OIC was assessed with the Bowel Function Index (BFI) in three consecutive visits. Absolute difference and Student’s t-test were used to compare BFI scores. Predictors (opioid compound and type, morphine-equivalent daily-dose [MEDD], and laxatives) were retrieved from the patients’ charts. BFI and predictors relationships were checked by multinomial logistic regression (MLR); independent predictors of BFI scores were assessed with χ2 analysis. Results: Of the 384 evaluations, 85 percent were on strong opioids with a MEDD range of 11-50 mg per day in the majority (60 percent) and 64 percent showed moderate constipation; 42 percent did not use laxatives while 24 percent used macrogol with significant decrease in the BFI. MLR showed that oxycodone was associated with a risk for moderate constipation. Lactulose and glycerin suppositories were associated with severe constipation. Non-opioid users and cancer patients were associated with normal bowel function and severe constipation, respectively. Conclusions: OIC was found in almost all evaluations of weak or strong opioid-users (97 percent); moderate to severe OIC was found in 72 percent of the evaluations. Cancer patients were associated with severe constipation. Macrogol was superior to other laxatives. In our experience, macrogol relieved constipation in those on the combination of oxycodone and naloxone and in those on fentanyl patches. Lactulose and glycerol suppositories were associated with severe constipation