# QT prolongation

Source: https://onco.cc/terms/qt-prolongation/  
OnCo record `qt-prolongation` (Term). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

A change on the heart's electrical trace, caused by some drugs blocking a potassium channel (hERG), that in rare cases sets off a dangerous rhythm. Drugs that do this need ECG checks and care with other medicines and low potassium or magnesium.

## Summary

Off-target hERG inhibition is common among kinase inhibitors (vandetanib, nilotinib, ribociclib, osimertinib, mobocertinib, selpercatinib, ivosidenib) and other drugs (arsenic trioxide, ondansetron, methadone); labels require baseline and periodic ECGs and electrolyte correction, and combining QT-prolonging drugs is avoided. Clinically important arrhythmia is rare, but QT prolongation has delayed or narrowed approvals and is screened for in early drug development (thorough QT studies). A QTc above 500 ms or an increase over 60 ms usually triggers dose interruption.

## Fields

- Kind: Term
- Last checked: 2026-09-09
- Also known as: QTc prolongation; QTc; QT interval; prolonged QT; QT; ECG monitoring; electrocardiogram; hERG; hERG inhibition; torsades; torsades de pointes; ventricular arrhythmia; electrolyte monitoring

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Long_QT_syndrome#Drug-induced
- Wikipedia: https://en.wikipedia.org/wiki/Long_QT_syndrome#Drug-induced

## Connected records

- terms: [Cardiotoxicity (LVEF decline, cardiomyopathy)](https://onco.cc/terms/cardiotoxicity/), [Therapeutic index (therapeutic window)](https://onco.cc/terms/therapeutic-index/), [Tyrosine kinase inhibitor (TKI)](https://onco.cc/terms/tki-term/)
- fronts: [Supportive Care & Survivorship](https://onco.cc/fronts/supportive-care/)
- drugs: [Arsenic trioxide](https://onco.cc/drugs/arsenic-trioxide/), [Nilotinib](https://onco.cc/drugs/nilotinib/), [Osimertinib](https://onco.cc/drugs/osimertinib/), [Ribociclib](https://onco.cc/drugs/ribociclib/)
- technologies: [Troponin and natriuretic peptide monitoring during cancer treatment](https://onco.cc/technologies/cardiac-biomarker-monitoring/)

---
JSON: https://onco.cc/api/v1/entities/qt-prolongation.json