Question: Warfarin is an anticoagulant drug and widely used in the prevention and treatment of various thro...
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Despite its long history of clinical use, warfarin is still a difficult medication to use in practice. This is due to the drug's narrow therapeutic index and wide inter-individual variability in patient response.
Narrow therapeutic index - In terms of therapeutic index, warfarin is highly effective when titrated to the proper level of anticoagulation, but it loses its efficacy when anticoagulation levels are too low. There is a substantial risk of serious bleeding problems when anticoagulation levels are too high. Insufficient levels of anticoagulation decrease the efficacy of warfarin significantly. Even at 1.9, the risk of thromboembolism rises sharply as the INR falls below 2. Furthermore, among warfarin patients who have a stroke, those who are under-anticoagulated at the time of the incident have substantially higher morbidity and mortality than those who are proper anticoagulation control.
Empirical dosing and Interpretation variability - The amount of warfarin a patient requires varies greatly. While the average maintenance dosage is 4–6 mg per day, different patients need a wide variety of doses (ranging from 4.5 to 77 mg per week) to achieve the same INR. These advantages are especially important during the warfarin initiation process, when the proper dose is being calculated. Since the initiation process is when anticoagulation control is most susceptible to dosing errors and when serious bleeding and thromboembolism can occur, it's important to get it right. To improve the drug's safety and efficacy while lowering costs and early discontinuations, efforts to improve our ability to predict warfarin maintenance dose are clearly required.
Why is it so difficult to keep patients on the drug? The reaction to warfarin is multifactorial and multigenetic, and patients have trouble adhering to therapy are the two main factors.
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