Hydroxychloroquine blood level monitoring may reduce toxicity risk in lupus

Hydroxychloroquine (HCQ) blood levels ≥1,150 ng/mL are associated with an increased risk of treatment-related toxicity, suggesting this threshold could guide HCQ dose adjustments in patients with systemic lupus erythematosus (SLE).

Dr Shivani Garg (University of Wisconsin School of Medicine and Public Health, WI, USA) presented the data from a pooled analysis aimed at determining an upper therapeutic limit for HCQ monitoring in clinical practice. This analysis included 1,843 participants from the Systemic Lupus International Collaborating Clinics (SLICC) Inception Cohort (33 centres in 11 countries across North America, Europe, and Asia), the Wisconsin Lupus Cohort Registry, and 3 French studies. Participants were eligible for inclusion in the analysis if they had whole blood and serum HCQ measurements at baseline, and the outcomes included HCQ-related toxicity.

Statistical analysis demonstrated that HCQ concentrations above 1,150 ng/mL did not improve clinical efficacy but were associated with a higher risk of toxicity. Multivariable regression analysis showed both age (per 10-year increase) and cumulative HCQ dose (per 1,000 g increase) significantly predicted HCQ toxicity, whereas other factors, including sex, race, and eGFR status, were not associated with increased odds of developing toxicity. Participants with HCQ blood levels of ≥1,150 ng/mL had a 2-fold higher risk of developing toxicity (adjusted OR 2.09; 95% CI 1.22-3.67; P=0.01).

Subgroup analysis by chronic kidney disease stage revealed that stages 3 and 4 were associated with approximately double the odds of exceeding the 1,150 ng/mL HCQ blood level threshold, even with weight-adjusted dosing.

“Safe and effective HCQ concentrations likely lie between 750-1,150 ng/mL,” concluded Dr Garg. “These findings support the role of therapeutic HCQ blood level monitoring to optimise efficacy and minimise toxicity, particularly in patients with chronic kidney disease stage 3 or higher.”

1. Garg S, et al. Defining safe hydroxychloroquine blood levels: Time to switch to precision monitoring for optimized lupus care. ACR Convergence, 24–29 October 2025, Chicago, IL, USA.

Medical writing support was provided by Mihai Surducan, PhD.

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Posted on 31 October 202531 October 2025