Drug interactions
Fosphenytoin + Levofloxacin
Severity: Moderate
Fosphenytoin and Levofloxacin: 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
Quinolones have been linked to both decreased and increased phenytoin levels in case reports, and they can also lower the seizure threshold. The direction and size of the effect are unpredictable.
What this interaction means in plain words
Fosphenytoin and Levofloxacin 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.
Fosphenytoin belongs to Central Nervous System; Levofloxacin belongs to Anti Bacterial.
Why it happens
Mechanism is not established; fluoroquinolones also have intrinsic proconvulsant activity.
What to do
Monitor for breakthrough seizures or phenytoin toxicity and check total or free phenytoin levels after starting or stopping levofloxacin. Adjust fosphenytoin dose to levels and clinical response.
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 Levofloxacin
- Dronedarone + Levofloxacin Contraindicated
- Ibutilide + Levofloxacin Contraindicated
- Levofloxacin + Thioridazine Contraindicated
- Levofloxacin + Vandetanib Contraindicated
- Levofloxacin + Ziprasidone Contraindicated
- Adagrasib + Levofloxacin Major
Other interactions of Fosphenytoin
- Dronedarone + Fosphenytoin Contraindicated
- Fosphenytoin + Ledipasvir-sofosbuvir Contraindicated
- Fosphenytoin + Lorlatinib Contraindicated
- Fosphenytoin + Lurasidone Contraindicated
- Fosphenytoin + Ranolazine Contraindicated
- Fosphenytoin + Sofosbuvir-velpatasvir-voxilaprevir Contraindicated
Frequently asked questions
Can I take Fosphenytoin with Levofloxacin?
MediHelp rates the interaction as moderate. Fosphenytoin and Levofloxacin 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. Quinolones have been linked to both decreased and increased phenytoin levels in case reports, and they can also lower the seizure threshold. The direction and size of the effect are unpredictable.
How serious is the interaction between Fosphenytoin and Levofloxacin?
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 for breakthrough seizures or phenytoin toxicity and check total or free phenytoin levels after starting or stopping levofloxacin. Adjust fosphenytoin dose to levels and clinical response.
What other medicines interact with Levofloxacin?
MediHelp also lists interactions of Levofloxacin with, for example, Dronedarone, Ibutilide, Thioridazine. The full list is on the Levofloxacin page.
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