Diazepam with Phenytoin Interaction Details
Brand Names Associated with Diazepam
- Diazepam
- Diazepam Intensol®
- Valium®
- Valrelease®
Brand Names Associated with Phenytoin
- Dilantin®
- Phenytek®
- Phenytoin
Medical Content Editor Dr. Brian Staiger, PharmD
Last updated
Nov 19, 2023
Interaction Effect
Alterations in serum phenytoin concentrations
Interaction Summary
Use caution with the concomitant administration of phenytoin and diazepam, as phenytoin levels may be decreased or increased . Consider obtaining phenytoin serum concentrations if concomitant administration is necessary. Phenytoin dose adjustments may be required, especially with the addition or withdrawal of diazepam .
Severity
Major
Onset
Unspecified
Evidence
Probable
How To Manage Interaction
Use caution with the concomitant administration of phenytoin and diazepam, as phenytoin levels may be decreased or increased . Consider obtaining phenytoin serum concentrations if concomitant administration is necessary. Phenytoin dose adjustments may be required, especially with the addition or withdrawal of diazepam .
Mechanism Of Interaction
Unknown
Literature Reports
A) Phenytoin toxicity occurred in a 44-year-old man who was given concomitant diazepam therapy. The patient complained of headache, nystagmus, diplopia, and ataxia and was admitted to the hospital. Aside from his long-standing seizure disorder, his past medical history was unremarkable. His antiepileptic regimen of phenytoin, phenobarbital, and lamotrigine had been unchanged for almost 5 months. Two weeks prior to admission his total phenytoin serum concentration was 8 mcg/mL. He was prescribed amoxicillin and diazepam 2 days prior to his hospital admission. His serum phenytoin concentration was 37 mcg/mL in the hospital. Diazepam and phenytoin were discontinued and the symptoms resolved .
Diazepam Overview
-
Diazepam is used to relieve anxiety and to control agitation caused by alcohol withdrawal. It is also used along with other medications to control muscle spasms and spasticity caused by certain neurological disorders such as cerebral palsy (condition that causes difficulty with movement and balance), paraplegia (inability to move parts of the body), athetosis (abnormal muscle contractions), and stiff-man syndrome (a rare disorder with muscle rigidity and stiffness). Diazepam is also used along with other medications to control seizures. Diazepam is in a class of medications called benzodiazepines. It works by calming abnormal overactivity in the brain.
Phenytoin Overview
-
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.
Return To Our Drug Interaction Homepage
Feedback, Question Or Comment About This Information?
Ask Dr. Brian Staiger, PharmD, our medical editor, directly! He's always more than happy to assist.
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.