RESUMO
<b>Purpose</b>: We report a case with portal vein stenosis that showed unexpected drowsiness induced by oral administration of low dose opioid, suggesting elevation of opioid level in blood. <b>Case report</b>: A 60-year-old woman developed portal vein stenosis caused by postoperative local recurrence and lymph node metastasis after operation of lower bile duct carcinoma. Her doctor administrated 10mg/day of oral controlled-release oxycodone tablet to her and she became drowsy. Therefore, we started powdered form of oral sustained release morphine with 10mg/day and reduced the dose to 5 mg/day; however, her drowsiness persisted. Finally, the symptom was remarkably improved when the administration was changed to a transdermal fentanyl patch (12.5μg/h). <b>Conclusion</b>: Adequate observation is required for cases with reduction in portal blood flow at the time of oral opioid administration. Because oral opioid can escape from first pass effect of the liver and opioid level in blood will be increasing. Furthermore, it is suggested that change in administration method from oral route to percutaneous one may be effective for improvement of adverse effects involving increased opioid-level in blood. Palliat Care Res 2008; 3(2): 331-334