Therapeutic warfarin dose dependence on age and smoking in acute pulmonary embolism

Initiation of warfarin therapy is being challenged, since the pharmacodynamics response has been slowed up and difficult to predict. The goal of anticoagulant therapy with warfarin is to administer the lowest dose of the drug to maintain the target international normalised ratio (INR) [1]. Study aim: To evaluate the dependence of therapeutic warfarin dose on age and smoking in acute pulmonary embolism (PE). Materials and methods: 125 consecutive patients (56% men; mean age 68±15 years) with newly diagnosed acute PE were prospectively examined. PE was confirmed by chest CT angiography. Patients, who suffered from sepsis, recurrent PE, operation or trauma in acute period, were excluded. 21% of all patients were smokers. Patients were divided in two groups: younger than 65 years and older than 65 years. A long term anticoagulation therapy was recommended to 78.4% of patients. INR ratio was monitored to assess the adequacy of warfarin therapy. Target INR range was 2-3. Results: For 43% of patients to achieve the target range of the INR took 3–7 days, whereas for 57% took more than a week. Smokers needed more time to achieve the therapeutic range of the anticoagulation comparing to non-smokers (11±4 days vs. 7,5±4 days, p = 0,002). The average dose of warfarin was 6±3 mg for the younger than 65 years old patients, and 4±1 mg for the older than 65 years patients. There was found a statistically significant inverse correlation between the therapeutic dose of warfarin and the patient9s age (r = –0.5, p Conclusions: Therapeutic dose of warfarin decreases with age. Smoking prolongs time, which is necessary to achieve the therapeutic dose of warfarin. 1.Chest 2012; 141 (2): e44S-e88S.