Hydroxychloroquine blood levels in stable lupus nephritis under low dose (2-3 mg/kg/day): 12-month prospective randomized controlled trial

Introduction: The American Academy of Ophthalmology (2016-AAO) recommended hydroxychloroquine (HCQ) dose not to exceed 5 mg/kg/day (real body weight). Recently, it was reported that prescribed 2016-AAO dose provided adequate HCQ levels for most lupus nephritis (LN) patients, with low flare risk. However, the minimum HCQ dose required to keep adequate levels is unknown.

Objectives: To evaluate if a further reduction in 2016-AAO dose (2-3 mg/kg/day) would sustain 12-month HCQ levels in LN patients with stable inactive disease.

Methods: Seventy-three stable LN patients under prescribed full HCQ 2016-AAO dose for ≥6 months and adequate baseline HCQ levels (≥613.5 ng/mL) were divided in two groups: reduced 2016-AAO dose (2-3 mg/kg/day), n = 32, and full 2016-AAO dose (5 mg/kg/day), n = 41. All patients were assessed at baseline, 3, 6, and 12 months. HCQ levels were measured by liquid chromatography-tandem mass spectrometry. Flare was defined as augment ≥ 3 in SLE Disease Activity Index-2000 and/or change in treatment. Rigorous clinical/laboratorial surveillance was performed.

Results: Prospective evaluation revealed for reduced 2016-AAO dose group a decrease of HCQ levels from baseline to 3 months (1,404.9 ± 492.0 vs. 731.6 ± 385.0 ng/mL, p < 0.01), and sustained levels at 6 months (p = 0.273) and 12 months (p = 0.091) compared to 3 months. For the full 2016-AAO dose group, a decrease occurred only from baseline to 12 months (1343.5 ± 521.5 vs. 991.6 ± 576.3 ng/mL, p < 0.001). Frequencies of patients with inadequate levels at 6 months was higher in reduced 2016-AAO group than full 2016-AAO dose (59% vs. 24%, p = 0.005), as well as at 12 months (66% vs. 32%, p = 0.002). Six-month and 12-month flare frequencies were comparable for both groups (p > 0.05).

Conclusions: Prescribed HCQ low-dose regimen (2-3 mg/kg/day) does not sustain, for most patients, 6- and 12-month adequate HCQ levels. Full 2016-AAO dose maintained HCQ levels way above this limit.

Trail registration: ClinicalTrials.gov : NCT03122431, registered on April 20, 2017 Key Points • Reduced American Academy of Ophthalmology (2016-AAO) hydroxychloroquine (HCQ) dose (2-3 mg/kg/day, real body weight) is unable to sustain HCQ blood levels within the safe cut-off defined for flare risk. • Full 2016-AAO dose (5 mg/kg/day) maintains a safe pattern of HCQ levels up to 12 months.