In lupus, in the case of thrombosis (clot in a venous or arterial vessel), especially in the context of an antiphospholipid antibody syndrome, an anticoagulant treatment may be prescribed.

How is this treatment usually managed?

Initially, anticoagulation based on heparin (most often low molecular weight (LMWH)) is used, which acts very quickly. LMWH is done by single or twice-daily injection, 12 hours apart. Very often this LMWH will be followed by an anticoagulant drug that can be taken orally and which belongs to the family of vitamin K antagonists (VKA) such as warfarin, and more rarely acenocoumarol.

These drugs work by blocking the synthesis of certain coagulation proteins. The anticoagulant effect of VKA is therefore delayed. Due to this latency time, heparin must be kept at an unchanged dose for as long as necessary, i.e. until the INR (International Normalized Ratio) is in the desired therapeutic zone for 2 consecutive days.

The INR is the biological test that allows the monitoring and adaptation of VKA (apart from any treatment with VKA, the INR of a normal subject is 1). Due to significant inter-individual variability, the dose of VKA is strictly individual.

The balance of treatment is sometimes achieved only after several weeks. After a change in dosage, INR checks are done regularly until stabilisation.

During an antiphospholipid antibody syndrome, the target INR is between 2 and 3 in venous thrombosis and 3 to 3.5 in arterial thrombosis. Other anticoagulants are now available (direct oral anticoagulants, with anti-Xa activity) that do not require INR monitoring but their level of effectiveness must be evaluated in lupus, especially in the case of antiphospholipid antibody syndrome. They are not recommended as first intention treatment.

Antiaggregant treatments, led by low-dose aspirin, prevent the formation of the “platelet clot”. These treatments work immediately and, in the case of aspirin, last up to 10 days after discontinuation. Antiaggregant treatment does not require biological monitoring. The initial dose is most often the equilibrium dose (often less than 100 mg for aspirin).

When you cut yourself, the platelets aggregate (like bricks) and plug the vascular breach. If you take aspirin, you will bleed longer in the event of cutting yourself.