The chief aim of drug treatment in patients with APS is to prevent blood clots or strokes.
The main drug used for many years has been warfarin, which thins the blood. There is good evidence from clinical trials that warfarin is effective in preventing clots in patients with APS.
There are some disadvantages to using warfarin. Patients have to have regular blood tests (called INR tests) to make sure that the level of thinning of the blood is at just the right level – if the dose of warfarin is too high there is an increased risk of bleeding. Furthermore, warfarin interacts with a number of other medications so that when those drugs are being taken the INR tests may need to be done more frequently.
Due to these issues with warfarin a new generation of blood-thinning drugs has been developed. These drugs are called Direct Oral Anticoagulants or DOACs and examples include rivaroxaban, apixaban and dabigatran. Their effect on blood thinning is more predictable and easier to control, so patients on these drugs do not require regular INR tests. It has also been suggested that these drugs have fewer interactions with other drugs than warfarin does.
The DOACs have been used to prevent clots in a number of other medical conditions and clinical trials have shown that they work as well as warfarin in those conditions. For this reason, some patients with APS have had their treatment changed from warfarin to DOACs.
The UK Medicines and Healthcare products Regulatory Agency (MHRA) has recently issued advice concerning use of DOACs in patients with APS. This advice may result in warfarin being preferred to DOACs for patients with APS until more evidence is available.
A number of medical specialist and patient groups in the UK are currently discussing this advice and we will be posting the outcome of those discussions when it is available.
In the meantime APS Support UK's advice to patients is as follows:
- If you are already taking a DOAC do not stop taking it until you have started an alternative blood-thinning agent such as warfarin. Remember that the highest risk of having a clot would be to take no blood-thinning agent at all. Your GP should not stop your DOAC without discussing it with your haematologist and local anticoagulation clinic first.
- If you are changed from a DOAC to warfarin you will need to start having regular INR blood tests and may need to take heparin injections until the warfarin starts to work and you reach your INR target range.
For more information, please visit the MHRA's website: https://www.gov.uk/drug-safety-update/direct-acting-oral-anticoagulants-doacs-increased-risk-of-recurrent-thrombotic-events-in-patients-with-antiphospholipid-syndrome