📈 QT Prolongation Risk & High-Risk Drugs
Quick reference to QT-prolonging drug classes, modifiable and patient risk factors, and management thresholds for torsades (TdP). Browser-side.
Risk multiplies when drug, electrolyte and patient factors stack.
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When to use
Bedside risk awareness before prescribing QT-prolonging agents. Look up authoritative per-drug ratings at CredibleMeds; compute the QTc value with this site's QTc tool.
How it works
Prolonged: men > 450 ms, women > 470 ms. High-risk: QTc > 500 ms or +60 ms from baseline. Keep K⁺ > 4.0 mmol/L and Mg²⁺ > 2.0 mg/dL.
Key points
- Risk multiplies when drug, electrolyte and patient factors stack.
- Correcting hypokalaemia/hypomagnesaemia and bradycardia markedly lowers TdP risk.
- Treat TdP with IV magnesium; consider pacing/isoprenaline.
- Avoid combining multiple QT-prolonging drugs.
References
Worked calculation
The values below come from this tool's own example placeholders and are computed server-side with the formula shown on this page, so the arithmetic can be checked quickly. It demonstrates how to substitute values only — it is not clinical advice and not a real case.
| View | High-risk drug classes |
|---|
→Quick referenceCommon QT-prolonging drug classes
- Antiarrhythmics IA/III：Quinidine, procainamide, disopyramide; sotalol, amiodarone, dofetilide, ibutilide
- Macrolides：Erythromycin, clarithromycin, azithromycin
- Fluoroquinolones：Moxifloxacin > levofloxacin > ciprofloxacin
| View | Thresholds & management |
|---|
→Quick referenceQTc thresholds & management
- Prolonged：Men > 450 ms, women > 470 ms
- High-risk：QTc > 500 ms or +60 ms from baseline — markedly increased TdP risk
- Monitoring：ECG (QTc) and electrolytes before and after dosing
Frequently asked questions
- What is QT Prolongation Risk & High-Risk Drugs?
- Quick reference to QT-prolonging drug classes, modifiable and patient risk factors, and management thresholds for torsades (TdP). Browser-side.
- How is QT Prolongation Risk & High-Risk Drugs calculated? What is the core formula?
- Prolonged: men > 450 ms, women > 470 ms. High-risk: QTc > 500 ms or +60 ms from baseline. Keep K⁺ > 4.0 mmol/L and Mg²⁺ > 2.0 mg/dL.
- When is QT Prolongation Risk & High-Risk Drugs used?
- Bedside risk awareness before prescribing QT-prolonging agents. Look up authoritative per-drug ratings at CredibleMeds; compute the QTc value with this site's QTc tool.
- What are the key clinical points for QT Prolongation Risk & High-Risk Drugs?
- Risk multiplies when drug, electrolyte and patient factors stack. Correcting hypokalaemia/hypomagnesaemia and bradycardia markedly lowers TdP risk. Treat TdP with IV magnesium; consider pacing/isoprenaline. Avoid combining multiple QT-prolonging drugs.
- What are the limits and cautions when using QT Prolongation Risk & High-Risk Drugs?
- For licensed clinicians and clinical researchers. Interpret results with history, investigations and local protocols; not a diagnosis or prescription, and not a substitute for multidisciplinary decision-making or local guidelines.
- How is QT Prolongation Risk & High-Risk Drugs calculated in practice? Can you show a worked example?
- Inputs: View High-risk drug classes → Result: Quick reference Common QT-prolonging drug classes（Antiarrhythmics IA/III: Quinidine, procainamide, disopyramide; sotalol, amiodarone, dofetilide, ibutilide, Macrolides: Erythromycin, clarithromycin, azithromycin, Fluoroquinolones: Moxifloxacin > levofloxacin > ciprofloxacin） Inputs: View Thresholds & management → Result: Quick reference QTc thresholds & management（Prolonged: Men > 450 ms, women > 470 ms, High-risk: QTc > 500 ms or +60 ms from baseline — markedly increased TdP risk, Monitoring: ECG (QTc) and electrolytes before and after dosing）