Keywords: 
• warfarin /
• amiodarone /
• drug interaction /
• pharmaceutical care

Abstract: Objective To explore the role of clinical pharmacists in analyzing and dealing with abnormal INR value fluctuations caused by the drug interaction of warfarin and amiodarone in a post heart valve replacement patient. Methods By comparing interactions between warfarin and other drugs, we investigated the drugs the patient was using, found the cause of unusual INR value fluctuations, and regulated warfarin dosage in time. After that, we intensified the monitoring of coagulation function and offered detailed pharmaceutical care to the patient. In addition, we studied the possible reasons for the phenomenon from the following aspects such as the drug action mechanisms of warfarin and amiodarone;the interaction mechanisms of the two drugs;the correlation of anticoagulation effects of warfarin, the dosage and concentration of combined use of these two drugs. Results The reason for unusal INR value fluctuations was identified as the drug interaction between warfarin and amiodarone. Amiodarone can enhance the anticoagulant effects of warfarin, increase the risk of bleeding. By stoping warfarin for 3 days, INR value was restored to the target range. Then we continued the anticoagulant therapy, and the condition of the patient was controlled steadily, and he was discharged smoothly. Conclusion Clinical pharmacists can help doctors find out problems related to drug therapy in time by providing effective pharmaceutical care to patients, so doctors may adjust the treatment in time. When using the drugs interacted with warfarin, we have to consider the those drug effects on anticoagulant therapy. In order to adjust regimens in time, we must understand the pharmacology and pharmacokinetics of the drugs we used at the same time;as well, we must intensify monitoring. Therefore, we can improve the safety and rationality of clinical medication, and also can provide better pharmaceutical care for patients.