Advances in the Clinical Use of Hydroxychloroquine Levels

Katherine Chakrabarti; W. Joseph McCune


Curr Opin Rheumatol. 2022;34(3):151-157. 

In This Article


Higher hydroxychloroquine blood levels may convey a protective effect against the risk of thrombosis–a feared complication of SLE. A 2021 study by Petri et al. reported a correlation between a lower mean hydroxychloroquine whole blood level and thrombotic events (720 vs. 935 ng/ml, P = 0.0247). The study included 739 patients enrolled in the Hopkins Lupus cohort, with an overall incident thrombosis rate of 5.1% (38 patients). Levels found to be protective against thrombosis in their cohort included: a mean whole blood level of at least 1068 ng/ml and a most recent whole blood level of at least 1192 ng/ml.[34]

A letter to the editor in Arthritis and Rheumatology by Kao et al. pointed out that although high whole blood levels of hydroxychloroquine may be protective against thrombosis, this increases the risk of retinopathy.[35] Petri et al.[23] in 2020 reported that by dividing hydroxychloroquine levels into tertiles, most toxicity occurred with blood levels of 1177–3513 ng/ml. If the level required to mitigate risk of thrombosis is 1068 ng/ml, this leaves only a very narrow therapeutic window between treatment and toxicity.