Question explored with the scientific record
Conversation so far
- 1 Hydroxychloroquine dangerous or not
- 2 Your answer is wrong
Answered on this page ↓
Your answer is wrong
The short version: the evidence on hydroxychloroquine cardiac toxicity is contradictory, and the strongest studies show no serious cardiac harm in outpatients, but the hospitalized data is weaker and the question was never studied head-to-head with unvaccinated controls.
The best evidence comes from a meta-analysis of five randomized trials in outpatients, which found no serious cardiac adverse events and no reported QT prolongation across any study [3]. One trial reported a single cardiac arrhythmia in each group (1/936 vs 1/469) [3]. A separate cluster-randomized trial of 2,314 contacts found cardiac palpitations in only 0.4% of the HCQ group and no difference in serious adverse events (14 vs 17) [4]. A small hospitalized cohort of 71 patients showed modest QTc prolongation (baseline 418 ms to 442 ms at 48 hours) with only 2 interruptions, both linked to concurrent QT-prolonging drugs [9].
The case reports and pharmacovigilance signals are real but weak evidence. Three case reports document QTc elongation over 500 ms [7], and a FAERS analysis flagged a signal for HCQ plus azithromycin [1]. A literature review found that adding azithromycin raised the rate of QTc over 500 ms from 3% to 21% [10]. But case reports cannot prove causation, and FAERS is a passive system that detects signals, not rates.
| Population | Design | Cardiac harm finding |
|---|---|---|
| Outpatients (5 RCTs) | Meta-analysis | No serious cardiac AEs, no QT prolongation reported [3] |
| Outpatient contacts (1 RCT) | Cluster-randomized | 0.4% palpitations, no difference in SAEs [4] |
| Hospitalized (1 cohort) | ECG monitoring | QTc +24 ms; 2/68 interruptions [9] |
| Case series (3 patients) | Case reports | QTc >500 ms [7] |
| FAERS database | Pharmacovigilance | Signal for HCQ+AZ [1] |
My call: for outpatients, the randomized evidence shows no serious cardiac toxicity from hydroxychloroquine alone. The risk rises when combined with azithromycin. For hospitalized patients, the evidence is too thin to call. Confidence: moderate for the outpatient finding, low for the hospitalized claim.
Sources examined 14
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Serious Cardiovascular Adverse Event Associated with Hydroxychloroquine with Azithromycin in Patient with COVID-19 : A Pharmacovigilance Analysis of the FDA Adverse Event Reporting System (FAERS)
A retrospective pharmacovigilance study using the FDA FAERS database to evaluate whether hydroxychloroquine (HCQ), alone or in combination with azithromycin (AZ), is associated with serious cardiovascular adverse events in COVID-19 patients, finding signals of increased risk and…
DOI: 10.36948/ijfmr.2022.v04i06.1012 -
Hydroxychloroquine in the primary thrombosis prophylaxis of antiphospholipid antibody positive patients without systemic autoimmune disease
This study aimed to evaluate the efficacy of hydroxychloroquine in preventing thrombosis in persistently antiphospholipid antibody-positive patients without systemic autoimmune diseases, but was terminated early due to low recruitment and no observed thrombotic events.
DOI: 10.1177/0961203317724219 - Randomized Controlled Trials of Early Ambulatory Hydroxychloroquine in the Prevention of COVID-19 Infection, Hospitalization, and Death: Meta-Analysis DOI: 10.1101/2020.09.30.20204693
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A Cluster-Randomized Trial of Hydroxychloroquine for Prevention of Covid-19
In this open-label, cluster-randomized trial conducted in Catalonia, Spain, postexposure hydroxychloroquine did not prevent SARS-CoV-2 infection or PCR-confirmed Covid-19 among asymptomatic contacts, though it caused substantially more adverse events than usual care.
DOI: 10.1056/NEJMoa2021801 -
Compassionate use of tocilizumab in severe SARS-CoV2 pneumonia
A retrospective, single-center cohort study of 186 patients with severe SARS-CoV-2 pneumonia treated with compassionate-use tocilizumab at Fundación Jiménez Díaz, showing high survival when tocilizumab was given at lower oxygen needs (FiO2 ≤0.5%), with limited adverse events and…
DOI: 10.1016/j.ijid.2020.10.045 -
Clodronate and hydroxychloroquine in erosive osteoarthritis: a 24-month open randomized pilot study
A 24-month open randomized pilot trial comparing intravenous/immediate clodronate to hydroxychloroquine for active erosive osteoarthritis of the hand found clodronate produced significant pain and functional improvements, while hydroxychloroquine was ineffective and poorly toler…
DOI: 10.3109/s10165-011-0506-8 -
Adverse Cardiac Events Related to Hydroxychloroquine Prophylaxis and Treatment of COVID-19
This paper presents three case reports of cardiac adverse events (QT interval prolongation, tachycardia, and arrhythmias) following hydroxychloroquine use, either alone or with other QT-prolonging drugs, for COVID-19 prophylaxis or treatment.
DOI: 10.36519/idcm.2020.0012 -
A Case of COVID mRNA Vaccine Linked Antiphospholipid Syndrome
A 22-year-old healthy male developed antiphospholipid syndrome with a large pulmonary embolus, markedly elevated triple-positive antiphospholipid antibodies, and multisystem symptoms after his second dose of an mRNA COVID vaccine, with negative COVID testing, and improved on api…
DOI: 10.33140/bscr.02.01.13 -
Low voltage areas defragmentation in sinus rhythm for radiofrequency ablation of persistent atrial fibrillation (SCAR-AF Study)
Close ECG monitoring in hospitalized COVID-19 patients treated with hydroxychloroquine and azithromycin showed modest QTc prolongation with rare therapy interruption; a separate multicenter SCAR-AF trial investigates defragmentation of low voltage atrial areas during persistent …
DOI: 10.1016/j.acvdsp.2020.10.230 -
The Potential Benefit of Beta-Blockers for the Management of COVID-19 Protocol Therapy-Induced QT Prolongation: A Literature Review
This literature review assesses whether cardio-selective beta-blockers, particularly bisoprolol, can mitigate QT interval prolongation caused by COVID-19 protocol therapies (chloroquine/hydroxychloroquine and azithromycin) and discusses potential additional benefits and underlyi…
DOI: 10.3390/scipharm88040055 -
COVID-19: Emergence, Spread, Possible Treatments, and Global Burden
A narrative overview of COVID-19 emergence, spread, provisional treatments, and global burden, summarizing current evidence for Remdesivir, convalescent plasma, hydroxychloroquine/chloroquine, lopinavir/ritonavir, corticosteroids, and vaccine development as of 2020.
DOI: 10.3389/fpubh.2020.00216 -
1321. Population Pharmacokinetic (PK) and Pharmacokinetic/Pharmacodynamic (PK/PD) Target Attainment Analyses for Dalbavancin in Pediatric Patients
Poster abstracts summarize antimicrobial pharmacokinetics/pharmacodynamics across diverse contexts (healthy volunteers, pediatric patients, burn patients, hospitalized adults) with route equivalence, PopPK modeling, biofilm PD, and QT-prolongation risk during the COVID era, high…
DOI: 10.1093/ofid/ofaa439.1503 -
A pragmatic randomized controlled trial reports lack of efficacy of hydroxychloroquine on coronavirus disease 2019 viral kinetics
In a pragmatic randomized trial of 53 hospitalized COVID-19 patients, hydroxychloroquine added to standard care did not significantly accelerate SARS-CoV-2 oropharyngeal viral load decline compared to standard care alone over five days.
DOI: 10.1038/s41467-020-19056-6 -
Urgent Guidance for Navigating and Circumventing the QTc-Prolonging and Torsadogenic Potential of Possible Pharmacotherapies for Coronavirus Disease 19 (COVID-19)
An urgent Mayo Clinic guidance document that outlines how to navigate and mitigate the QTc-prolonging and torsadogenic risks of repurposed COVID-19 pharmacotherapies (notably chloroquine/hydroxychloroquine and related agents) through baseline and on-treatment QTc monitoring, ris…
DOI: 10.1016/j.mayocp.2020.03.024