Low Blood Concentration of Hydroxychloroquine in Patients With Refractory Cutaneous Lupus Erythematosus

OBJECTIVE: To study the relation between blood concentration of hydroxychloroquine and the clinical efficacy of hydroxychloroquine sulfate in a series of patients with cutaneous lupus erythematosus (CLE). DESIGN: Prospective multicenter study. A staff dermatologist blinded to blood hydroxychloroquine concentrations performed a standardized review of medical records and assessment of hydroxychloroquine efficacy in the following 3 categories: complete remission, partial remission (clearing of >50% of skin lesions), or treatment failure. Whole-blood samples were collected for measurement of blood hydroxychloroquine concentration. SETTING: Fourteen French university hospitals. PATIENTS: Three hundred consecutive patients with subacute or chronic CLE who had been treated with hydroxychloroquine for at least 3 months. MAIN OUTCOME MEASURES: The statistical significance of correlation between blood hydroxychloroquine concentration and efficacy of hydroxychloroquine and the statistical associations in univariate and multivariate analyses of complete remission with several variables. RESULTS: The study included 300 patients with discoid lupus erythematosus (n = 160), subacute CLE (n = 86), lupus erythematosus tumidus (n = 52), chilblain lupus (n = 26), and lupus panniculitis (n = 16); 38 of these patients had 2 or more associated forms. Median blood hydroxychloroquine concentration was significantly higher in patients with complete remission (910 [range, <50 to 3057] ng/mL) compared with partial remission (692 [<50 to 2843] ng/mL) and treatment failure (569 [<50 to 2242] ng/mL) (P = .007). In the multivariate analysis, complete remission was associated with higher blood hydroxychloroquine concentrations (P = .005) and the absence of discoid lesions (P = .004). Thirty patients (10.0%) had very low blood hydroxychloroquine concentrations (<200 ng/mL) and may be considered nonadherent to the treatment regimen. CONCLUSION: Monitoring hydroxychloroquine blood concentrations might improve the management of refractory CLE.