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Causality: well established
Causality assessment · Causality: well established
Hydroxychloroquine and QT prolongation: is the FAERS signal real?
A written Bradford Hill assessment of one drug–event pair. The grade is a judgement about the signal, not a statement that this drug causes this event in any one person; FAERS counts are reports, not rates.
Hydroxychloroquine ↔ QT prolongation
n=921 co-reports · PRR 7.4 · ROR 7.5
Hydroxychloroquine is an antimalarial and immunomodulator used in lupus and rheumatoid arthritis; it blocks cardiac potassium channels and can prolong the QT interval, carried here as 921 co-reports (PRR 7.4). Risk rises with high dose, hypokalaemia, and co-administration of other QT-prolonging drugs, and the label advises caution and ECG monitoring in at-risk patients.
Regulatory basis: hydroxychloroquine prescribing information — QT prolongation and ventricular-arrhythmia caution.
| Bradford Hill viewpoint | Status | Note |
|---|---|---|
| Temporality (necessary) | met | QT change during therapy |
| Strength | met | PRR 7.4, moderate |
| Consistency | met | Reproduced across case series |
| Specificity | partial | Shared with other 4-aminoquinolines |
| Biological gradient | met | Higher with higher dose |
| Plausibility | met | Cardiac potassium-channel blockade |
| Coherence | met | Fits the mechanism |
| Experiment | n/a | Not a trial endpoint |
| Analogy | met | Analogous to chloroquine QT prolongation |
This table is this page's own qualitative read of the literature cited above, not an automated or citation-gated assessment — see the note at the bottom of this page.
✗ No ClinicalTrials.gov results-posting trial in the top search hits for hydroxychloroquine captured qt prolongation as a tracked adverse event in a usable structure. QT prolongation is an electrocardiographic finding that requires monitoring, so arthritis trials did not capture it as a coded event.