Medical information to help you stay in control
Have you just found out from your doctor that you need to start taking an oral anticoagulant? Or are you already taking an oral anticoagulant but would like to have more information?
Oral anticoagulants, such as warfarin and phenprocoumon, which are known under brand names such as Coumadin®, Jantoven®, Marevan®, Lawarin®, Waran® and Warfant®, are used to prevent the development of blood clots. Collectively known as Vitamin K antagonists (VKAs), these drugs have been used for over 60 years and doctors are very familiar with their effects and safety profile. Scientific studies and clinical experience show that VKAs are very effective in reducing the risk of stroke and have few side-effects.
The human body has a complex mechanism called coagulation that causes blood to clot if a wound occurs. Under normal circumstances this is desirable; it allows the body to heal itself. Yet in some clinical conditions, coagulation can cause unwanted blood clots that may lead to complications and can be life threatening.
Anticoagulants are commonly prescribed for the following conditions:
- Atrial Fibrillation (AF)
AF is a disorder of the heart rhythm and is common in older people (it affects nearly 10% of people over 80). In healthy individuals, a regular heart rate of between 60 and 100 beats per minute at rest is normal, but patients with AF may have periods of very low or very high heart rate (up to 175 beats per minute).
In the heart of a person with AF, the heart quivers, or fibrillates, rapidly and irregularly rather than beating effectively. This leads to symptoms such as palpitations and shortness of breath. It also means that blood flow within the heart itself can become sluggish and there is a risk of clot formation on the walls lining the heart, especially within the chamber known as the atrium. This can lead to a heart attack.
Anticoagulants lengthen the time it takes for blood to clot, and therefore reduce the risk of a clot developing.
- Mechanical heart valves
Modern heart surgery has transformed the lives of many people who were either born with, or developed as they grew older, damaged heart valves. When heart valves are damaged, the problem is either that the valve is narrowed or that it no longer fully closes.
They can now be replaced with either a ‘biological’ valve, e.g. a pig heart valve treated for use in humans, or a mechanical valve made out of synthetic material.
Mechanical heart valves are more durable, however there is an increased risk of clot formation. To reduce the risk of clotting your doctor may prescribe an oral anticoagulant.
- Venous thromboembolism
Deep Vein Thrombosis (DVT) occurs when a blood clot forms in a vein. It usually develops in the calf muscle, less frequently in the thigh and sometimes in other deep-lying veins in your body.
Some of the common symptoms of a DVT are:
- Tenderness in the leg
- Swelling and a feeling of tightness, the skin may feel "stretched".
- However some DVTs have no symptoms at all.
There may be increased risk of DVT under conditions of:
- Prolonged immobility, for example long journeys where you sit still without being able to stretch your legs or move about
- A medical condition that restricts normal movement or activity
- Surgery such as orthopaedic surgery or illness that requires treatment such as chemotherapy
- Genetic or inherited conditions
- Existing vein damage from a previous DVT
- The contraceptive pill and hormone replacement therapy
Some people may only realise they have a DVT when a pulmonary embolism develops as a result of the blood clot in the leg breaking away and being carried to the lungs in the blood stream. Pulmonary Embolism is a very serious condition.
A Pulmonary Embolism (PE) is a blood clot in the lung that usually originates from smaller blood vessels in the leg. A clot from a DVT travels to the lungs and through the vessels of the lung until it reaches smaller vessels where it becomes lodged. The clot then prevents any further blood from travelling to that section of the lung which can eventually lead to stroke.
Common symptoms may include:
- Chest pain that is sharp and is worse when taking a deep breath
- Shortness of breath
- Low blood pressure
All the above can also be symptoms for other conditions; however Pulmonary Embolism can be life threatening so if you are concerned, seek the advice of a doctor or go to your nearest accident and emergency department.
People that experience a PE may be in hospital for several days until their anticoagulant medication is introduced and stabilised. They may remain on anticoagulation therapy for six months or longer.
Ensuring effective anticoagulant treatment
Effective anticoagulation treatment requires monitoring
Taking the correct dose is crucial for efficient anticoagulation treatment. The correct dose is established by measuring how long it takes your blood to clot. This is called the International Normalized Ratio (INR)1.
- An INR of 1 is normal and is found in people who are not taking warfarin2
- An INR of 2 means that your blood takes twice as long to clot as normal3
- An INR of 3 means that your blood takes three times as long to clot as normal3
Your doctor will provide you with a target INR range, depending on your indication.
As your response to treatment may be affected by several factors, such as the food you eat, it is important to monitor regularly.
- Wardrop D et al (2008) Br J Haematol 141:757-763
- http://www.anticoagulation.com.au/AboutWarfarin/INREssentials/WhatistheINR/tabid/106/Default.aspx last accessed June 2012
- Atrial Fibrillation Association Australia Warfarin Therapy Fact Sheet
- Levi M et al (2009) Semin Thromb Hemost 35:527-542
Coagulation Self-Testing with CoaguChek®
It is important to keep your blood’s clotting time within the range prescribed by your doctor. You may need to take your anticoagulant for a few weeks, months or even for the rest of your life. But no matter how long, your levels need to be regularly measured and that’s where PT/INR self-testing is a great benefit.
Self-monitoring can increase your safety on anticoagulants
Have the peace of mind that you know your PT/INR value when needed, home or away. Self-monitoring only requires a drop of blood and results are available within a minute. Results can either be reported to your doctor or nurse who will adjust your warfarin dose for you or you can learn how to adjust the dose yourself.
With self-monitoring you can test your INR whenever and wherever you like
- No more time consuming trips to the hospital or to your local surgery
- Don’t worry about holidays – you can take your INR meter with you
- You no longer need to take time off work to attend hospital or GP appointments