What Hydroxychloroquine Level do we Target?
A target therapeutic hydroxychloroquine level is not established in part as there is also no current standardization of hydroxychloroquine levels across various labs. Numerous studies have suggested levels of 500–1000 ng/ml as a therapeutic target.
In particular, several studies have focused levels needed for the prevention of lupus flares. In the PLUS study, a randomized control trial to evaluate the effects of targeting a hydroxychloroquine level at least 1000 ng/ml on the incidence of systemic lupus erythematosus (SLE) flares, increasing the dose of hydroxychloroquine to achieve levels at least 1000 ng/ml did not decrease the number of SLE flares over 7 months of follow-up. However, adherence increased in the control group and only 39% of the treatment group stayed above the 1000 ng/ml goal threshold. Conversely, in two retrospective observational studies, Cunha et al. reported that a hydroxychloroquine level greater than 600 ng/ml was associated with decreased likelihood of renal flares in patients with lupus nephritis, and Pedrosa et al. reported that persistently low hydroxychloroquine levels less than 613.5 ng/ml best predicted risk of flares in 82 patients with lupus nephritis.
Curr Opin Rheumatol. 2022;34(3):151-157. © 2022 Lippincott Williams & Wilkins