OBJECTIVES: : Unit-dose drug distribution system allows to provide patient individually packaged medications in our inpatient setting. When the doctor solely changed order of dosage, however, the system indicated the pharmacy to provide an identical package of medication with only different amounts, which produced unused drugs being stocked on wards that require to return. The difficulty of managing drug return is labor-consuming and not cost-effective. The objective of this study is to modify change order system to minimize drug return rate, and to evaluate the financial impact of this approaches. METHODS: During January through August 2011, among 270,000 dispensed prescription per month, twenty percent (approximately 50,000 medications) were returned. Therefore, in September 2011, We add a calculation function to the system that allows to identify how many needed drugs pharmacy should dispensed when dosage change by minusing the amount of drugs left on wards. RESULTS: : The intervention suggests approximately 60 % reduction in drug return rate was noted through the modified system. Via the modified system, the numbers of daily drug return were dramatically dropped form 2176 previously to 1143 in October 2011, and gradually reduced to 887 in November. Moreover, the estimated cost avoidance will reach NT 1,110 million per day based on the average cost of NT 861.16 per medication.  CONCLUSIONS: This study demonstrated that modifying change order system were able to prevent drugs being stocked on wards, reduce drug return rate and drug wasting as well.