Drug interactions
Phenindione + Quinidine
Severity: Moderate
Phenindione 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
Quinidine has been reported to enhance the effect of oral anticoagulants, and phenindione is a vitamin K antagonist, so bleeding risk may increase. The size of the effect is uncertain.
What this interaction means in plain words
Phenindione 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
Possible additive anticoagulant effect, as quinidine can reduce vitamin K-dependent clotting factor synthesis and may alter anticoagulant metabolism.
What to do
Monitor INR more frequently when starting or stopping quinidine and adjust the phenindione dose accordingly.
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 Phenindione with Quinidine?
MediHelp rates the interaction as moderate. Phenindione 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. Quinidine has been reported to enhance the effect of oral anticoagulants, and phenindione is a vitamin K antagonist, so bleeding risk may increase. The size of the effect is uncertain.
How serious is the interaction between Phenindione 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 INR more frequently when starting or stopping quinidine and adjust the phenindione dose accordingly.
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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