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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. [ABSTRACT FROM AUTHOR]

Objectives: It is unknown if hydroxychloroquine blood level dynamics impact flare rates in lupus nephritis patients. We prospectively evaluated hydroxychloroquine levels to determine which blood-based patterns are more associated with disease activity. Methods: In total, 82 lupus nephritis patients under a prescribed hydroxychloroquine dose of 4–5.5 mg/kg actual body weight (maximum 400 mg/day) for ≥3 months were evaluated at baseline and 7 months. Hydroxychloroquine blood levels were determined by liquid chromatography-tandem mass spectrometry. Flare was defined as increase ≥3 in the Systemic Lupus Erythematosus Disease Activity Index 2000 score and/or a change or increase in therapy. Results: Overall, 9/82(11%) patients had flares during follow-up and had lower baseline hydroxychloroquine blood levels than those without flares (220.4 (53.5–1471.1) vs. 1006.3 (53.5–2137.8) ng/ml, p = 0.013). The hydroxychloroquine blood level cut-off that best predicted flares was 613.5 ng/ml (odds ratio = 8.67, 95% confidence interval: 1.66–45.18, p = 0.006). For 77 (94%) patients, the 7-month hydroxychloroquine level dynamics was evaluated and revealed: 59/77 (77%) had a persistent pattern of adequate (41/77(53%)) or fluctuating (18/77 (23%)) levels, with a low and comparable risk of flares (2/41 (5%) vs. 1/18 (5%), p = 1.000). The remaining group had persistent low levels (18/77 (23%)) and their flare frequency was significantly higher than the adequate group (5/18 (28%) vs. 2/41 (5%), p = 0.023). The frequencies of adequate/inadequate hydroxychloroquine blood levels in patients were comparable at baseline and 7 months (McNemar's test, p = 0.480). Conclusion: We provide novel evidence that hydroxychloroquine blood-level patterns (persistently low, adequate, or intermittent) have distinct impacts on flare rates in lupus nephritis patients. These findings reinforce the need of routine hydroxychloroquine measurements to maintain the appropriate blood levels. [ABSTRACT FROM AUTHOR]