Correlation of Hydroxychloroquine Whole Blood Levels With Real and Ideal Body Weight Dosing and Development of...

To examine the correlation between hydroxychloroquine levels with real body weight and ideal body weight dose and identify patient characteristics at risk for subtherapeutic or supratherapeutic dosing.

A retrospective chart review of 181 patients with lupus (429 unique hydroxychloroquine whole blood levels) was performed. Hydroxychloroquine levels <100 (indicating medication noncompliance) were excluded (n = 26). Summary statistics, linear regression of hydroxychloroquine level and real body weight/ideal body weight, and odds ratios (ORs) for factors associated with supratherapeutic (>2000 ng/mL) or subtherapeutic (<750 ng/mL) hydroxychloroquine levels were calculated.

The correlation of real body weight and hydroxychloroquine level was r = 0.124. Ideal body weight and hydroxychloroquine level had a correlation of r = 0.324. The OR of body mass index (BMI) >30 kg/m² and supratherapeutic hydroxychloroquine level was 4.95 (95% CI, 1.98-12.39). The OR of BMI <20 kg/m² and subtherapeutic hydroxychloroquine level was 2.90 (95% CI, 1.58-5.37). Three of 71 patients screened for toxicity had hydroxychloroquine maculopathy. These subjects had mean hydroxychloroquine levels of 1314 ng/mL (range, 1101-1553 ng/mL), 2402 ng/mL (range, 1754-3050 ng/mL), and 1223.8 ng/mL, and BMIs of 20.8 kg/m², 29.7 kg/m², and 19.8 kg/m², respectively.

All dosing schedules show variability in hydroxychloroquine levels. Ideal body weight may correlate more strongly with hydroxychloroquine level than real body weight. Under real body weight-based guidelines, obesity may increase the risk for supratherapeutic hydroxychloroquine levels, and low weight may increase the risk for subtherapeutic levels.