Levofloxacin with Phenytoin Interaction Details
Brand Names Associated with Levofloxacin
- Levaquin®
- Levofloxacin
Brand Names Associated with Phenytoin
- Dilantin®
- Phenytek®
- Phenytoin
Medical Content Editor Dr. Brian Staiger, PharmD
Last updated
Jan 04, 2024
Interaction Effect
Decrease in phenytoin levels
Interaction Summary
In 2 case reports, coadministration of levofloxacin and phenytoin resulted in difficulty achieving therapeutic levels of phenytoin despite repeated increases of phenytoin dosage. High dosages of phenytoin were needed to reach plasma concentrations in the therapeutic range until levofloxacin was discontinued. In one case, the patient was rechallenged with levofloxacin and had a similar decrease in phenytoin levels. The Drug Interaction Probability Scale rated these interactions as probable.
Severity
Moderate
Onset
Unspecified
Evidence
Probable
How To Manage Interaction
In 2 case reports, coadministration of levofloxacin and phenytoin resulted in difficulty achieving therapeutic levels of phenytoin despite repeated increases of phenytoin dosage. High dosages of phenytoin were needed to reach plasma concentrations in the therapeutic range until levofloxacin was discontinued. In one case, the patient was rechallenged with levofloxacin and had a similar decrease in phenytoin levels. The Drug Interaction Probability Scale rated these interactions as probable.
Mechanism Of Interaction
Unspecified
Literature Reports
A) A 46-year-old man receiving valproic acid and phenytoin for non-convulsive epileptic status following a triple coronary bypass and receiving levofloxacin for suspected ventilator-associated pneumonia, required high dosages of phenytoin to reach plasma concentrations in the therapeutic range. Levofloxacin was discontinued resulting in adequate phenytoin plasma levels. Levofloxacin was subsequently reintroduced and despite high phenytoin doses, once again resulted in a decrease in phenytoin levels. Levofloxacin was discontinued a second time and phenytoin dosage was decreased resulting in an increase in phenytoin levels after 48 hours. The Drug Interaction Probability Scale rated this interaction as probable .
B) A 31-year-old man with severe craniocerebral trauma was receiving levofloxacin for ventilator-associated pneumonia and prophylactic phenytoin. Despite the administration of a phenytoin loading dose, levels were subtherapeutic and repeated dosage increases were required. When levofloxacin was discontinued, the free fraction of phenytoin increased to greater than 100%. The Drug Interaction Probability Scale rated this interaction as probable .
Levofloxacin Overview
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Levofloxacin is used to treat certain infections such as pneumonia, and kidney, prostate (a male reproductive gland), and skin infections. Levofloxacin is also used to prevent anthrax (a serious infection that may be spread on purpose as part of a bioterror attack) in people who may have been exposed to anthrax germs in the air, and treat and prevent plague (a serious infection that may be spread on purpose as part of a bioterror attack. Levofloxacin may also be used to treat bronchitis, sinus infections, or urinary tract infections but should not be used for bronchitis and certain types of urinary tract infections if there are other treatment options available. Levofloxacin is in a class of antibiotics called fluoroquinolones. It works by killing bacteria that cause infections.
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Antibiotics such as levofloxacin will not work for colds, flu, or other viral infections. Using antibiotics when they are not needed increases your risk of getting an infection later that resists antibiotic treatment.
Phenytoin Overview
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Phenytoin is used to control certain type of seizures, and to treat and prevent seizures that may begin during or after surgery to the brain or nervous system. Phenytoin is in a class of medications called anticonvulsants. It works by decreasing abnormal electrical activity in the brain.
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Definitions
Severity Categories
Contraindicated
These drugs, generally, should not be used together simultaneously due to the high risk of severe adverse effects. Combining these medications can lead to dangerous health outcomes and should be strictly avoided unless otherwise instructed by your provider.
Major
This interaction could result in very serious and potentially life-threatening consequences. If you are taking this drug combination, it is very important to be under close medical supervision to minimize severe side effects and ensure your safety. It may be necessary to change a medication or dosage to prevent harm.
Moderate
This interaction has the potential to worsen your medical condition or alter the effectiveness of your treatment. It's important that you are monitored closely and you potentially may need to make adjustments in your treatment plan or drug dosage to maintain optimal health.
Minor
While this interaction is unlikely to cause significant problems, it could intensify side effects or reduce the effectiveness of one or both medications. Monitoring for changes in symptoms and your condition is recommended, and adjustments may be made if needed to manage any increased or more pronounced side effects.
Onset
Rapid: Onset of drug interaction typically occurs within 24 hours of co-administration.
Delayed: Onset of drug interaction typically occurs more than 24 hours after co-administration.
Evidence
Level of documentation of the interaction.
Established: The interaction is documented and substantiated in peer-reviewed medical literature.
Theoretical: This interaction is not fully supported by current medical evidence or well-documented sources, but it is based on known drug mechanisms, drug effects, and other relevant information.
How To Manage The Interaction
Provides a detailed discussion on how patients and clinicians can approach the identified drug interaction as well as offers guidance on what to expect and strategies to potentially mitigate the effects of the interaction. This may include recommendations on adjusting medication dosages, altering the timing of drug administration, or closely monitoring for specific symptoms.
It's important to note that all medical situations are unique, and management approaches should be tailored to individual circumstances. Patients should always consult their healthcare provider for personalized advice and guidance on managing drug interactions effectively.
Mechanism Of Interaction
The theorized or clinically determined reason (i.e., mechanism) why the drug-drug interaction occurs.
Disclaimer: The information provided on this page is for informational purposes only and should not be considered medical advice. Always consult with a qualified healthcare professional regarding your specific circumstances and medical conditions.
Where Does Our Information Come From?
Information for our drug interactions is compiled from several drug compendia, including:
The prescribing information for each drug, as published on DailyMED, is also used.
Individual drug-drug interaction detail pages contain references specific to that interaction. You can click on the reference number within brackets '[]' to see what reference was utilized.
The information posted is fact-checked by HelloPharmacist clinicians and reviewed quarterly.