Orfarin Special Precautions

If a rapid antithrombotic effect is needed, heparin treatment must be initiated. After this, heparin treatment is continued along with the initiated warfarin treatment for at least 5 to 7 days until the INR has been at target level (see Dosage & Administration) for at least two days.
Resistance to warfarin is a very rare phenomenon. Only a few case reports have been published on that. These patients need 5- to 20-fold warfarin doses to achieve therapeutic response. If the response of the patient to warfarin treatment is significantly poorer than normal, other causes imparing the effect of the treatment must be first be ruled out, eg, missing drug intake, interaction with food or other medicinal products and potential laboratory errors.
To avoid coumarin necrosis (see Adverse Reactions), patients with a hereditary deficiency of protein C or S should first start heparin for 5 to 7 days along with warfarin therapy. Warfarin therapy is initiated at a dose of 5 mg.
Special caution must be exercised when treating elderly patients. The patients compliance and the abilities to follow strict rules on drug intake must be ascertained. Hepatic metabolism of warfarin as well as the synthesis of coagulation factors are slowed down in the elderly. This may be easily result in an excessive therapeutic response. Warfarin therapy must be initiated cautiously (see Dosage & Administration). Concomitant medications must be taken into account to avoid harmful interactions (see Interactions).
Hyperthyroidism, fever and uncompensated heart failure may enhance the warfarin effect. In hypothyroidism, the warfarin effect may be reduced. In moderate hepatic insufficiency, the effect of warfarin is enhanced. In renal insufficiency and nephrotic syndrome, the free fraction of warfarin in plasma is elevated (depending on the other primary diseases, it may either enhance or reduce the warfarin effect). The clinical situation of the patient and the INR values must be carefully monitored under all these circumstances.
The tablets contain lactose. Patients with rare hereditary problems of galactose intolerance, the Lapp lactase deficiency of glucose-galactose malabsorption should not take this medicine.
Effects on the Ability to Drive or Operate Machinery: No effect.