Drug interactions
Phenytoin + Quinine
Severity: Moderate
Phenytoin and Quinine: 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
Phenytoin induces quinine metabolism and can substantially lower quinine concentrations, risking treatment failure in malaria. Quinine may also affect phenytoin levels in some patients.
What this interaction means in plain words
Phenytoin and Quinine 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.
Phenytoin belongs to Central Nervous System; Quinine belongs to Anti Parasitic.
Why it happens
Phenytoin induction of CYP3A4 increases quinine clearance.
What to do
Monitor clinical and parasitological response to quinine and consider an alternative antimalarial; check phenytoin levels and adjust if seizure control or toxicity changes.
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 Quinine
- Arsenic trioxide + Quinine Contraindicated
- Dofetilide + Quinine Contraindicated
- Dronedarone + Quinine Contraindicated
- Ibutilide + Quinine Contraindicated
- Mefloquine + Quinine Contraindicated
- Nilotinib + Quinine Contraindicated
Other interactions of Phenytoin
- Artemether / lumefantrine + Phenytoin Contraindicated
- Bictegravir + Phenytoin Contraindicated
- Cabotegravir + Phenytoin Contraindicated
- Doravirine + Phenytoin Contraindicated
- Elbasvir / grazoprevir + Phenytoin Contraindicated
- Elvitegravir / cobicistat / emtricitabine / tenofovir df + Phenytoin Contraindicated
Frequently asked questions
Can I take Phenytoin with Quinine?
MediHelp rates the interaction as moderate. Phenytoin and Quinine 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. Phenytoin induces quinine metabolism and can substantially lower quinine concentrations, risking treatment failure in malaria. Quinine may also affect phenytoin levels in some patients.
How serious is the interaction between Phenytoin and Quinine?
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 clinical and parasitological response to quinine and consider an alternative antimalarial; check phenytoin levels and adjust if seizure control or toxicity changes.
What other medicines interact with Quinine?
MediHelp also lists interactions of Quinine with, for example, Arsenic trioxide, Dofetilide, Dronedarone. The full list is on the Quinine page.
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