Drug interactions
Encainide + Quinidine
Severity: Moderate
Encainide and Quinidine: moderate interaction.
Last updated
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Encainide is converted by CYP2D6 to active metabolites (O-demethyl encainide) that contribute most of its antiarrhythmic effect. Quinidine blocks CYP2D6 and mimics the poor-metabolizer state, raising parent encainide and lowering active metabolite formation. This changes the effect profile and may increase proarrhythmic and conduction effects.
What this interaction means in plain words
Encainide and Quinidine can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Why it happens
Quinidine potently inhibits CYP2D6, blocking encainide conversion to its active metabolites.
What to do
Monitor ECG for PR and QRS prolongation and for arrhythmia, and titrate encainide to response. Consider avoiding combined class I antiarrhythmics.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
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Other interactions of Quinidine
- Adagrasib + Quinidine Contraindicated
- Arsenic trioxide + Quinidine Contraindicated
- Artemether / lumefantrine + Quinidine Contraindicated
- Chloroquine + Quinidine Contraindicated
- Dofetilide + Quinidine Contraindicated
- Dronedarone + Quinidine Contraindicated
Frequently asked questions
Can I take Encainide with Quinidine?
MediHelp rates the interaction as moderate. Encainide and Quinidine can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Encainide is converted by CYP2D6 to active metabolites (O-demethyl encainide) that contribute most of its antiarrhythmic effect. Quinidine blocks CYP2D6 and mimics the poor-metabolizer state, raising parent encainide and lowering active metabolite formation. This changes the effect profile and may increase proarrhythmic and conduction effects.
How serious is the interaction between Encainide and Quinidine?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor ECG for PR and QRS prolongation and for arrhythmia, and titrate encainide to response. Consider avoiding combined class I antiarrhythmics.
What other medicines interact with Quinidine?
MediHelp also lists interactions of Quinidine with, for example, Adagrasib, Arsenic trioxide, Artemether / lumefantrine. The full list is on the Quinidine page.
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