If you’re living with a condition like atrial fibrillation or thrombosis, it’s likely that you’ve been prescribed warfarin to stop blood clotting. Warfarin was the only available oral blood thinning medication for over 50 years. In recent years, however, a new group of drugs called DOACs have been approved for use in the UK. These avoid the need for regular blood tests, while reducing your risk of major bleeding compared to warfarin. We spoke to leading consultant haematologist Dr Carolyn Millar to find out when a doctor should consider prescribing one of these new drugs.
What are DOACs?
DOAC stands for “Direct oral anticoagulant”, sometimes also referred to as NOACs. Four DOACs are now licensed and available in the UK:
How do they compare to warfarin?
The most striking benefit of DOACs is the reduced risk of serious bleeding, in particular the risk of intracranial haemorrhage compared with taking warfarin.
In terms of the patient experience, the main advantage of these new drugs is that, unlike warfarin, the effect is predictable and so for the vast majority of patients’ blood test monitoring is not required. DOACs are also far less influenced by your diet and other medicines you may be taking. The lack of need for regular blood test monitoring means far greater convenience than if you were taking warfarin.
Patients sometimes worry that there isn’t always a way to directly reverse or switch off the effect of DOACs in the event of severe bleeding. However, antidotes are now becoming available and a number of others are in development. Furthermore, there are other products that can be given to reduce the blood thinning effect of DOACs in the event of severe bleeding Studies show that bleeding is less common and less serious compared with bleeding associated with warfarin and the duration of effect or ‘on-off’ effect of DOACs is much shorter than warfarin so direct reversal is required far less than for warfarin.
Still, there are situations where DOACs are not recommended:
- if you have severe liver disease or impairment
- if you have mechanical heart valves
- if you weigh more than 120kg
Finally, a doctor might not recommend a DOAC for you simply because there is no data yet on the effects of the drug on someone with your condition.
Which is the best one for me?
Although these drugs are generally very similar in mode of action and effect, there are currently no direct comparative trials between these drugs. However, there is plenty to consider in terms of the effect of a particular drug might in an individual patient including the effect of other conditions a patient might have:
- Weight and age – you might require a lower DOAC dose if you are have a lower body weight or are over the age of 80.
- Chronic kidney disease – most DOACs can be used in patients with mild kidney disease at a reduced dose. Some DOACs are less reliant on the kidneys for elimination making them a more suitable choice. At the moment DOACs are usually avoided in patients with more severe forms of kidney disease.
- Interaction with other drugs – if you take another drug to reduce arrhythmias, such as verapamil, amiodarone or quinidine, your doctor might decide you need a lower DOAC dose. On the other hand the blood thinning effect of DOACs can be reduced by some medications, including the commonly prescribed drugs for epilepsy, making their use unsuitable as the dose cannot be increased.
- Gastrointestinal bleeding – some types of DOAC are associated with higher rates of gastrointestinal bleeding than others, so your doctor should assess your risk of bleeding when making a choice about a DOAC.
As with any medication, you should follow your doctor’s instructions as to when and how often you should take DOACs and which ones you should take.