Warfarin

Before taking this medicine

Do not take warfarin if you are allergic to warfarin or any ingredient in the tablets. It must not be used during pregnancy, except in some women with mechanical heart valves who are at high risk of blood clots, where the benefits may outweigh the risks. Warfarin can cause serious birth defects, bleeding in the unborn baby, miscarriage and fetal death. Warfarin must not be used in people with: • A tendency to bleed or certain blood disorders. • Recent or planned brain, spinal cord or eye surgery, or traumatic surgery leaving large open wounds. • Bleeding tendencies linked to active ulcers or bleeding in the digestive, urinary, genital or respiratory tract; bleeding in the brain or spinal cord; a brain aneurysm; a tear in the wall of the aorta; inflammation or fluid around the heart; or bacterial infection of the heart’s inner lining. • Threatened miscarriage, eclampsia or preeclampsia. • Severe high blood pressure known as malignant hypertension. • Conditions making it very unlikely they can follow treatment instructions without supervision. Warfarin must not be used during a spinal puncture, other procedures that could cause uncontrollable bleeding, or major regional or lumbar block anaesthesia. Important precautions include tissue death or gangrene, serious calcium buildup in small blood vessels called calciphylaxis, and blockages caused by fragments of fatty plaque or cholesterol. These can be severe or fatal and may require warfarin to be stopped by the treating clinician. Excessive anticoagulation with blood in the urine can cause acute kidney injury. People with kidney impairment need frequent INR blood tests to monitor warfarin’s effect. Warfarin must not be started as initial treatment for heparin-induced thrombocytopenia, a fall in platelets caused by heparin, because amputation and death have occurred. It may be considered once the platelet count has returned to normal. If breastfeeding, monitor the infant for bruising or bleeding.