Drug interactions
Lidocaine + Phenytoin
Severity: Moderate
Lidocaine and Phenytoin: 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 hepatic enzymes and can lower lidocaine concentrations, potentially reducing antiarrhythmic effect. Additionally, both drugs have cardiac depressant effects, and intravenous use together can add to myocardial depression.
What this interaction means in plain words
Lidocaine and Phenytoin 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.
Lidocaine belongs to Cardiovascular; Phenytoin belongs to Central Nervous System.
Why it happens
Phenytoin induces CYP3A4 and other enzymes, increasing lidocaine clearance; additive cardiac depression is also possible.
What to do
When lidocaine is used as an antiarrhythmic, monitor response and ECG and adjust the dose accordingly; avoid rapid intravenous phenytoin during lidocaine infusion.
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 Lidocaine
- Bupivacaine liposome + Lidocaine Major
- Disopyramide + Lidocaine Major
- Ex vivo expanded autologous human corneal epithelial cells containing stem cells + Lidocaine Major
- Lidocaine + Nirmatrelvir / ritonavir Major
- Lidocaine + Ombitasvir / paritaprevir / ritonavir and dasabuvir Major
- Lidocaine + Pimozide Major
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 Lidocaine with Phenytoin?
MediHelp rates the interaction as moderate. Lidocaine and Phenytoin 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 hepatic enzymes and can lower lidocaine concentrations, potentially reducing antiarrhythmic effect. Additionally, both drugs have cardiac depressant effects, and intravenous use together can add to myocardial depression.
How serious is the interaction between Lidocaine and Phenytoin?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: When lidocaine is used as an antiarrhythmic, monitor response and ECG and adjust the dose accordingly; avoid rapid intravenous phenytoin during lidocaine infusion.
What other medicines interact with Lidocaine?
MediHelp also lists interactions of Lidocaine with, for example, Bupivacaine liposome, Disopyramide, Ex vivo expanded autologous human corneal epithelial cells containing stem cells. The full list is on the Lidocaine page.
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