QT prolongation multi-drug checker
Add medications to see the combined QT prolongation risk profile. Flags Known Risk drug combinations. Reference lookup based on CredibleMeds.org classifications and FDA labeling.
No medications added yet.
Combined QT risk profile
Add medications to see the analysis.
Reference data current as of July 2026. Sources: CredibleMeds.org (Arizona CERT); FDA prescribing information.
About this tool
QT prolongation from multiple drugs is a common real-world scenario, particularly in older adults on antipsychotic plus antibiotic plus antiemetic combinations. This tool takes a list of medications and classifies each by CredibleMeds Known/Possible/Conditional risk category, then flags combinations of two or more Known Risk drugs.
Standard clinical guidance: any patient starting a Known Risk QT drug, or combining two or more QT drugs, should have a baseline ECG. QTc above 500 ms or a rise of more than 60 ms from baseline is the standard concern threshold. See our QTc side effect page for full clinical framing.
Non-drug risk factors amplify effect: hypokalemia, hypomagnesemia, bradycardia, female sex, congenital long QT, preexisting heart disease, and age. Correcting electrolytes and reviewing drug list is often the first intervention when QT prolongation is found.
Common questions
- What is the CredibleMeds classification?
CredibleMeds.org (Arizona CERT) maintains the standard reference for QT-prolonging drugs. Categories: Known Risk (well-documented QT prolongation and torsades), Possible Risk (may prolong QT), and Conditional Risk (QT prolongation only in specific conditions). This tool draws on that classification.
- What QTc is clinically concerning?
QTc above 500 ms is the accepted threshold for clinical concern about torsades de pointes. A rise of more than 60 ms from baseline is also concerning. See our QTc side effect page for full detail on management thresholds and clinical action.
- Does this tool replace an ECG?
No. It flags drug combinations pharmacologically. Actual QT effect requires an ECG. Every patient starting a Known Risk QT drug or combining multiple QT drugs should have a baseline and follow-up ECG per FDA labeling.