Patients with antiphospholipid syndrome (APS) who are taking the anticoagulation drug rivaroxaban are twice as likely to have a thrombotic event compared with warfarin, researchers say.
A randomised trial recently published in Annals of Internal Medicine found that recurrent thrombosis events occurred in 11.6% of patients taking rivaroxaban compared with just 6.3% taking vitamin K antagonists (VKAs).
The study included 190 patients with thrombotic APS from university hospitals in Spain. One group of patients was prescribed rivaroxaban (15mg/d or 20mg/d) and the other group were prescribed dose-adjusted VKAs.
Of the participants, who were aged 18 to 75 years, 90% had a high global antiphospholipid score at baseline and all participants were considered to be at high risk of thrombosis.
In the three years follow up, recurrent thrombotic events in the rivaroxaban group were mainly arterial with a high rate of stroke.
“Rivaroxaban did not demonstrate non-inferiority to dose-adjusted VKAs for secondary thromboprophylaxis in patients with thrombotic APS,” the study authors said. “Instead, our results indicate a recurrent thrombotic rate that is nearly double, albeit without statistical significance.”
But the reasons rivaroxaban failed to prevent arterial thrombotic events in patients with APS was uncertain.
Professor Denis Wahl, a co-author and a vascular medicine specialist at the University of Lorraine in France, said that while APS patients with non-provoked thrombosis were usually treated with long term vitamin K antagonists, this study confirmed that rivaroxaban was not a good treatment alternative.
“Patients should not switch their treatment to rivaroxaban as this study confirms that current treatment with vitamin K antagonists is preferable,” he told Rheumatology Republic.
However, he warned there were some patients who were given rivaroxaban because they had an unstable international normalised ratio (INR) and didn’t respond to VKAs.
“Some guidelines propose to treat these cases of thrombotic APS with rivaroxaban but these patients are an exception and should be closely monitored,” Professor Wahl said.
In addition, Professor Wahl said for the patients who were already taking rivaroxaban it was important clinicians talk to them about the risk of the treatment.
“High risk patients will probably be switched to vitamin K antagonists while low risk patients who are doing well on rivaroxaban and have taken this treatment for a long time without any thrombotic recurrence may choose to continue this treatment for practical reasons but they must be fully informed and carefully monitored,” he said.
Any patients with an APS diagnosis following a thrombotic event should be prescribed vitamin K antagonists, most often warfarin as standard, the study authors concluded.