The antimalarial drug hydroxychloroquine is frequently prescribed to treat symptoms of the autoimmune disease lupus. In addition to decreasing disease flares, the drug can also prevent blood clots, which are a major problem in individuals with lupus. A new study in Arthritis & Rheumatology shows that monitoring patients’ blood levels of hydroxychloroquine can predict their clotting risk.

In 739 patients, clotting occurred in 38 patients (5.1%). Average hydroxychloroquine blood levels were lower in patients who developed clots, and clotting rates were reduced by 12% for every 200 ng/mL increase in the most recent hydroxychloroquine blood level.

The finding may help clinicians determine the optimal dosing of hydroxychloroquine in patients with lupus.

«Hydroxychloroquine blood levels can be used to monitor adherence, benefits, and risks in lupus,» said lead author Michelle Petri, MD, MPH, of the Johns Hopkins University School of Medicine.

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