Hydroxychloroquine administration increased both complement C3 and C4 levels in patients with lupus, with a more pronounced effect on C4, particularly at blood levels over 50 ng/mL, according to a recent study.
A study published in Arthritis Care & Research assessed the impact of hydroxychloroquine (HCQ) on complement levels in patients with systemic lupus erythematosus (SLE). Conducted with over 3,000 patients from the Hopkins Lupus Cohort, study investigators evaluated HCQ's effects on complement C3 and C4 levels, which are markers of disease activity and organ damage in SLE.
Specifically, 44% of patients with HCQ levels above 50 ng/mL achieved normal C4 levels, compared to 13% with lower HCQ levels.
In an analysis of all clinical visits, patients with HCQ blood levels exceeding 200 ng/mL were more likely to have normal C4 levels. The odds of achieving normalized C4 levels increased by up to 2.72 times in these patients, indicating a dose-dependent relationship.
The study observed significant improvement in complement levels, especially C4, when hydroxychloroquine was initiated and in patients with higher whole blood levels of the drug. Hydroxychloroquine may help prevent poor outcomes in SLE by modulating the mechanisms that lead to complement consumption.
Full disclosures can be found in the original study.