Source: Medxiv

Abstract

Background: Chloroquine (CQ) and Hydroxychloroquine (HCQ) have recently been suggested as treatment for the current Corona Virus Disease 2019 (COVID-19) pandemic. However, despite their long-term use and only few case reports on adverse effects, CQ and HCQ are listed as a known risk of the lethal ventricular arrhythmia Torsade de Pointes and their cardiac safety profile is being questioned. Thus, we aimed to investigate the electrocardiographic and mortality effects of CQ and HCQ in a primary care population.

Methods: We used Danish health care registers and electrocardiograms (ECGs) from primary care to define three studies. 1) A paired study of subjects with ECGs before and during use of CQ/HCQ, 2) a matched ECG study of subjects taking CQ/HCQ compared to controls, and 3) a mortality study on people taking HCQ matched to control. In both matched studies, we adjusted for connective tissue diseases, use of QT-prolonging drugs, and cardiac disease.

We used the QTc interval as the marker for electrocardiographic safety. In the mortality study, cases were followed from first claimed prescription until 300 days after estimated completion of the last prescription. 95% confidence intervals follow estimates in parenthesis.

Results: Use of CQ was associated with a 5.5 (0.7;10) ms increase in QTc in the paired study (n=10). In the matched study (n=28, controls=280), QTc was insignificantly increased in subjects taking CQ by 4.7 (-3.4;13) ms. With a ΔQTc of 1.0 (-5.6;7.5), use of HCQ was not associated with an increased QTc in the paired study (n=32). In the matched study (n=172, controls=1,720), QTc also was not different between groups (p=0.5). In the mortality study (n=3,368), use of HCQ was associated with a hazard ratio of 0.67 (0.43;1.05).

Conclusions: In subjects free of COVID-19, we found a small increase in QTc associated with use of chloroquine, but not hydroxychloroquine. We found no increased mortality associated with use of hydroxychloroquine.

Competing Interest Statement

The authors have declared no competing interest.

Funding Statement

No external funding was received.

Author Declarations

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

Yes

The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

The Danish Data Protection Agency approved the use of de-identified data (2007-58-0015) on the conditions that the exact number of subjects in groups of < 3 subjects not be disclosed and that no calculations (including p-values) be reported on groups of < 5 subjects.

All necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived.

Yes

I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).

Yes

I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable.

Yes

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