Opioid-induced bowel dysfunction in healthy volunteers assessed with questionnaires and MRI

OBJECTIVEOpioid treatment is associated with numerous gastrointestinal adverse effects collectively known as opioid-induced bowel dysfunction (OIBD). Most current knowledge of the pathophysiology derives from animal studies limited by species differences and clinical studies, which have substantial confounders that make evaluation difficult. An experimental model of OIBD in healthy volunteers in a controlled setting is therefore highly warranted. The aim of this study was to assess bowel function in healthy volunteers during opioid treatment using subjective and objective methods. METHODSTwenty-five healthy men were assigned randomly to oxycodone or placebo for 5 days in a cross-over design. The analgesic effect was assessed with muscle pressure algometry and adverse effects were measured using questionnaires including the bowel function index, gastrointestinal symptom rating scale, patient assessment of constipation symptoms and the Bristol stool form scale. Colorectal volumes were determined using a newly developed MRI method. RESULTSCompared with baseline, oxycodone increased pain detection thresholds by 8% (P=0.02). Subjective OIBD was observed as increased bowel function index (464% increase; P