Whole blood drug levels do not correlate with QTc intervals in hydroxychloroquine-treated systemic lupus erythematosus patients

Abstract

Abstract Objectives HCQ is recommended for all patients with SLE, but reports of cardiac toxicity in severe acute respiratory syndrome coronavirus 2 patients raised concerns. We aimed to study the relationship between HCQ blood levels and QTc intervals. Methods A retrospective review of 90 SLE patients (cohort 1) was conducted with data collected regarding demographics, QTc interval and chronic kidney disease (CKD). A prospective study of 84 SLE patients (cohort 2) was conducted with data collected regarding demographics, dose of HCQ, duration of HCQ treatment, presence of echocardiographic abnormalities and CKD simultaneous with whole blood HCQ levels measured by HPLC. Statistical analysis utilized one-way analysis of variance, Pearson’s correlation coefficient and t tests. Results In cohort 1 there was no significant difference in mean QTc based on 75 HCQ-treated [437.91 msec (s.d. 20.02)] as compared with 15 untreated patients [434.6 msec (s.d. 27.49)]. In patients with CKD, the mean QTc in HCQ users [448 (s.d. 23.37)] as compared with non-users [444.5 msec (s.d. 24.61)] also had no significant difference. In cohort 2, HCQ levels did not correlate with QTc interval (r = 0.017) and this applied regardless of the dose prescribed (r = 0.113 for 400 mg and r = 0.06 for 200 mg), duration of exposure (P = 0.36 for 0–5, >5–10 or >10 years), CKD (r = 0.482) or underlying cardiac abnormalities (r = 0.430). Conclusions This is the first study relying on measured blood levels demonstrating the absence of a clinically consequential increase in QTc levels in HCQ-treated SLE patients.