Orfarin Dosage/Direction for Use

The target INR range of oral anticoagulant therapy: Prophylaxis of thromboembolic complications in patients with prosthetic heart valves: INR 2.5-3.5. Other indications: INR 2.0-3.0.
Adults: Patients in normal weight and the spontaneous INR under 1.2 are administered 10 mg of warfarin on three consecutive days. The dosing is continued according to the table as follows based on the INR measured on the fourth day.
In open care and for patients with inherited protein C or protein S deficiency the recommended initial dose is 5 mg of warfarin (*) in three days. The dosing is continued according to the table as follows, based on the INR-measured on the fourth day. (See Table 1.)
For elderly patients, for those small in size, for those with the spontaneous INR over 1.2, or for those who have a disease (see Precautions) or medication (see Interactions) affecting the efficacy of anticoagulant therapy, the recommended initial dose is 5 mg of warfarin (*) for two days. The dosing is continued according to table 2, based on the INR measurement performed on the third day. (See Table 2.)

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INR measurements are carried out daily until the therapeutic level has been achieved (usually this takes 5 to 6 days). Intervals of INR measurements are then extended weekly. In long-term follow-up the measurement intervals are dependent i.a. on the patient's compliance and clinical status, targeting, however, on 4-weekly measurement intervals. If large fluctuations exist in the INR values or if the patient has a disease affecting liver function or the absorption of vitamin K, the measuring interval must be shorter than this. Many medicines may potentiate or weaken the effect of warfarin, which must be considered in the follow-up when initiating or discontinuing other medications. In long-term follow-up the adjustments required based on the INR measurements are made to the weekly dose. Thereafter the effect of the adjustment is checked by measuring the INR after 1 or 2 weeks of the adjustment. After this, the intervals are targeted on the same 4-weekly measurement intervals.
Children: The initiation and follow up of anticoagulant therapy in children is carried out by pediatricians. Dosage can be adjusted according to Table 2. (See Table 2.)

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Elective Surgery: Pre-, peri- and postoperative anticoagulant therapy the following dosage can be applied (if an urgent reversal of oral anticoagulant effect is needed, see Overdose).
Determine the INR one week prior to the scheduled surgery. Discontinue warfarin 1 to 5 days prior to surgery. If the patient is in high risk of thromboembolism, subcutaneous low molecular weight heparin should be given at therapeutic doses. The effect of heparin can be monitored by measuring the prophylactic effect of FXa when the effective therapeutic level is 0.3 to 0.7 anti-FXa activity units/mL.
The extent of warfarin pause depends on the INR value. Discontinue warfarin: 5 days prior to surgery if the INR > 4.0; 3 days prior to surgery if the INR=3.0 to 4.0; 2 days prior to surgery if the INR=2.0 to 3.0.
Determine the INR in the evening before surgery. If INR >1.8, administer 0.5 to 1 mg vitamin K₁ intravenously or orally.
Consider the need for unfractionated heparin infusion or prophylactic low molecular weight heparin during the day of surgery.
Continue subcutaneous low molecular weight heparin for 5 to 7 days concomitantly with reintroduced warfarin therapy.
Initiate warfarin with maintenance doses in the evening after minor surgery, and on the day the patient begins enteral nutrition after major surgery.