UNLABELLED: Opioid-induced constipation (OIC) is a side effect of opioid therapy that can affect quality of life, adherence to treatment, and morbidity and possibly mortality. OBJECTIVES: To investigate whether docusate sodium, sennosides, and lactulose have equal efficacy and side effect profiles compared to PEG in the management of OIC in adults. METHODS: A systematic review was undertaken. Randomized controlled trials of adults taking opioids for cancer or non-cancer pain were considered if they met inclusion criteria. CONCLUSIONS: Statistical pooling was not possible as no studies met inclusion criteria. Large, well-powered, randomized controlled trials are feasible. Standard definitions of OIC would assist with the execution of these studies and contribute to their internal and external validity. Further research is strongly encouraged.