Hydroxychloroquine: a multifaceted treatment in lupus

Abstract

The efficacy of antimalarials, especially hydroxychloroquine (HCQ), in preventing systemic lupus erythematosus (SLE) flares is well demonstrated. However, many studies show that the percentage of SLE patients treated with HCQ remains low. By blocking the toll-like receptor 7 and 9 in plasmacytoid dendritic cells, HCQ inhibits interferon-alpha production which plays a crucial role in SLE pathogenesis. In addition to reducing damage accrual in SLE patients, HCQ appears to protect against the occurrence of diabetes, thrombotic events, and dyslipidemia. As a consequence, some studies have suggested that HCQ, which is inexpensive, has a protective effect on survival in SLE patients. Thanks to the pharmacokinetic properties of HCQ (long half-life) and to the availability of its blood assay, very low or undetectable blood HCQ concentrations are a valuable marker of non-adherence to treatment, thus adding a new benefit to HCQ prescriptions. The main side effect of HCQ is retinal toxicity. This complication is very rare, but may be potentially severe, thus requiring regular screening. Retinal toxicity remains the only absolute contra-indication of HCQ in adult SLE patients. Other contra-indications are few and rare. During pregnancy and breast-feeding, HCQ continuation is not only allowed but recommended. In conclusion, the risk/benefit ratio of HCQ is excellent. Many now believe that all SLE patients should be offered this treatment.