Anticoagulants i.e. Warfarin Flashcards
What are the indications of warfarin?
prophylaxis of embolisation in rheumatic heart disease and atrial fibrillation, prophylaxis of embolisation after insertion of prosthetic heart valve, prophylaxis and treatment of venous thrombosis and pulmonary embolism, transient ischaemic attacks.
What are the contraindications of warfarin?
avoid within 48 hours postpartum, haemorrhagic stroke, or significant bleeding.
What is the mechanism of action of warfarin?
Warfarin decreases blood clotting by blocking the enzyme vitamin K epoxide reductase that reactivates vitamin K1.
Without sufficient active vitamin K1, clotting factors II, VII, IX, and X have decreased clotting ability. The anticlotting protein C and protein S are also inhibited but to a lesser degree. A few days are required for full effect to occur and these effects can last for up to five days.
What are the common/very common unwanted side effects of warfarin?
haemorrhage/bleeding.
What are the monitoring requirements of warfarin?
The base-line prothrombin time should be determined but the initial dose should not be delayed whilst awaiting the result. It is essential that the INR (international normalised ratio - how long it takes for blood to clot, higher INR = longer it takes to clot/higher risk of bleeding) be determined daily or on alternate days in early days of treatment, then at longer intervals (depending on response), then up to every 12 weeks.
INR needs to stay in range of 1-2 for most patients, needs to be regularly monitored in initial stages to determine ideal dose. In severe renal impairment, monitor INR more frequently. Any change in patient’s clinical condition, particularly associated with liver disease, intercurrent illness, or drug administration, necessitates more frequent testing.
What is the patient/carer advice for warfarin?
Anticoagulant treatment booklets should be issued to all patients/carers. These include advice for patients on anticoagulant treatment, an alert card to be carried by the patient at all times, and a section for recording of INR results and dosage information. Counsel patients/carers on signs/symptoms of bleeding (bruising, bleeding gums, red/dark brown urine, red/black bowel motions, nosebleeds, coughing up blood or blood in your spit, trouble breathing or swallowing, heavier than usual menstrual period, bleeding from cuts, wounds and scrapes that takes longer to stop, dark or blood-stained vomit, severe headache/dizziness, and unexplained pain, swelling or discomfort).
