Higher hydroxychloroquine blood levels reduce thrombosis risk in SLE
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Thrombosis rates among patients with systemic lupus erythematosus decrease 13% for every increase of 200 ng/mL in mean hydroxychloroquine in the blood, according to data presented at the EULAR 2020 virtual congress.
“It is well known that hydroxychloroquine reduces the thrombosis risk in lupus,” Michelle A. Petri, MD, MPH, of Johns Hopkins University, told attendees in the webcast. “We asked particularly about hydroxychloroquine whole blood levels.”
To analyze the link between hydroxychloroquine blood levels and thrombotic events among patients with SLE, Petri and colleagues studied a cohort of 812 participants. The cohort included 93% women, 43% African-American patients and 46% white people. Additionally, all had hydroxychloroquine blood measurements prior to thrombosis, quantified by liquid chromatography-tandem mass spectrometry.
The researchers calculated the mean hydroxychloroquine blood levels throughout all cohort visits prior to occurrence of thrombosis for each patient. Thrombotic events were defined as venous — including DVT/PE or other venous — or arterial thrombosis, such as stroke, myocardial infarction, digital gangrene or other arterial conditions.
According to Petri, thrombosis occurred in 43 patients during prospective follow-up, 3% of which were venous cases and 2.9% of which were arterial. Lupus anticoagulant was strongly associated with a history of any thrombosis (OR = 3.25), venous thrombosis (OR = 3.53) and arterial thrombosis (OR = 3.08). Further, a prospective analysis demonstrated that for any thrombosis and for venous thrombosis, blood levels for hydroxychloroquine were significantly lower.
In a separate, cross-sectional analysis, higher prescribed doses of hydroxychloroquine — as opposed to blood levels — were also associated with a decreased risk for any thrombosis (OR = 0.88) and venous thrombosis (OR = 0.83) for each 1 mg/kg increase in prescribed dose.
“Everyone wants to know what hydroxychloroquine blood level we should target,” Petri said. “It appears that about 1,000 to 1,500 [mg/dL] might be ideal. To conclude, the rate of thrombosis is reduced 13% for every 200-nanogram per mL increase in the mean hydroxychloroquine blood level. In addition, rates of thrombosis are reduced 12% for every 200-nanogram per mL increase in the most recent hydroxychloroquine level.”
“Therapeutic blood monitoring may inform thrombotic risk stratification and personalize hydroxychloroquine dosing strategies in patients with SLE, much more so than the prescribed dose,” she added. “Empirical dose reduction — meaning following the ophthalmology guidance — could reduce or eliminate this benefit of hydroxychloroquine.”
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Petri MA. Hydroxychloroquine blood levels and risk for thrombotic events in systemic lupus erythematosus. Presented at EULAR 2020 Congress; June 3-6, 2020; Virtual.
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