<p>Whenever possible, the baseline prothrombin time should be determined but the initial dose should not be delayed whilst awaiting the result.<br />
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<strong>Use in adults</strong>: The usual adult induction dose of warfarin is 10 mg daily for 2 days. The subsequent maintenance dose depends upon the prothrombin time, reported as INR (international normalized ratio). The daily maintenance dose of warfarin is usually 3 to 9 mg (taken at the same time each day). The maintenance dose is omitted if the prothrombin time is excessively prolonged. Once the maintenance dose is established in the therapeutic range, it is rarely necessary to alter. In emergencies, anticoagulant therapy should be initiated with heparin and warfarin together. Where there is less urgency, as in patients disposed to or at special risk of thromboembolism, anticoagulant therapy may be initiated with warfarin alone. Control tests must be made at regular intervals and maintenance dosage further adjusted according to the results obtained.<br />
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<strong>Use in children</strong>: Safety and efficacy in children &lt;18 years old have not been established. However, there is evidence of use and the initial dose is usually 0.1 mg.kg-1.d-1&nbsp;adjusted subsequently to aim for an INR range the same as in adults.</p>