A new study examined the optimal dosing of hydroxychloroquine in patients with systemic lupus erythematosus, finding that stable doses of 200 mg/day (or 3.0 to 3.5 mg/kg/day) may be effective in maintaining prolonged remission.

In the observational study, published in Lupus Science & Medicine, investigators analyzed data from 150 patients newly diagnosed with systemic lupus erythematosus (SLE) in the Lupus-Cruces cohort, all of whom had at least 5 years of follow-up. The study found that stable doses of 200 mg/day (or 3.0 to 3.5 mg/kg/day) were effective in maintaining prolonged remission, with 72% of patients achieving remission as defined by the Definitions of Remission in SLE criteria for 5 consecutive years.

Despite concerns about reducing hydroxychloroquine (HCQ) dosages below 5 mg/kg/day, the study found no significant difference in the remission rates of patients receiving 2.9 mg/kg/day and those receiving 3 mg/kg/day (P = .5). Notably, HCQ dosing didn't differ between patients with different baseline disease activity (mild, moderate, or severe), suggesting consistent dosing may be effective regardless of disease severity. Additionally, prednisone use remained low across all groups, averaging 2.3 mg/day over the 5-year period.

The study confirmed that the mean daily HCQ dose remained stable over time, averaging 194.6 mg/day. None of the patients in the cohort were treated with doses ≥ 5 mg/kg/day, and 98% of patients remained on HCQ throughout the follow-up period. Retinal toxicity, a known adverse effect of long-term HCQ use, was not reported in patients treated with stable 200 mg/day doses. The findings aligned with prior research indicating that toxicity risks increase primarily at doses > 5 mg/kg/day.

Earlier studies, including analyses from the Systemic Lupus International Collaborating Clinics (SLICC) cohort and Massachusetts General Hospital cohort, indicated an increased risk of SLE flares when HCQ doses were reduced below 5 mg/kg/day. However, the Lupus-Cruces cohort findings supported the efficacy of stable 200 mg/day dosing without increased flare risk. Notably, the 200 mg/day dosing has been the standard of care at this institution for over 20 years.

"Our study supports the use of stable doses of 200 mg/day (or 3.0 [to] 3.5 mg/kg/day) of HCQ in patients with SLE," the study authors explained, emphasizing the need for further comparative studies evaluating HCQ doses above and below 5 mg/kg/day to better assess the balance between efficacy and safety. A key limitation acknowledged by the investigators was their inability to directly compare outcomes between patients receiving 200 mg/day vs 400 mg/day, which would provide more definitive evidence for optimal dosing strategies.

No conflicts of interest were disclosed in the study.