In hospitals, computerized provider order entry (CPOE) with Clinical Decision Support System (CDSS) would decrease respectable amount of medication errors in prescribing stage. However, medication errors occur not only in prescribing stage, but also in administering stage. In this study we constructed an integrated drug information system (IDIS) for inpatients. To reduce medication errors in administering stage, IDIS is constructed on a computerized drug cart and could provide patients' data, drug information with drug images, drug administration routes, drug interactions, and intravenous drug compatibility information. By offering these helpful information, care workers in Taiwan could easily find medication errors as well. IDIS have been constructed and been demonstrated by patients' information from a medical center in Taipei. The primary results showed that 16.3% of inpatients still had drug interaction concerns, i.e. every patient suffered approximately 0.35 drug interaction in average. It seems that except for CPOE with CDSSs, it could be helpful using such a system to prevent medication errors.