Abstract: A 86-year-old male patient with atrial fibrillation was given warfarin for anticoagulation therapy in hospital. The international normalized ratio(INR) of the patient fluctuated during the period of therapy. Clinical pharmacists analysed disease,drug-drug interactions and other influence factors,combined with the characters of pharmacokinetics and pharmacodynamics to provide physicians with some reasonable advices. Clinical pharmacists also provided medication education to the patient, and played an important role in the safety of drug use.

Key words: atrial fibrillation, warfarin, anticoagulation, influence factor