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تعداد آیتم قابل مشاهده باقیمانده : 3 مورد
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Some interactions between phenytoin or fosphenytoin and other antiseizure medications*

Some interactions between phenytoin or fosphenytoin and other antiseizure medications*
Interacting drugs Effects (probable mechanism) Management
Phenytoin or fosphenytoin, with:
  • Brivaracetam
Decreased brivaracetam effect (increased metabolism by CYP2C19) Monitor clinical status
Possible phenytoin toxicity (decreased metabolism by CYP2C19) Monitor clinical status and phenytoin concentrations
  • Carbamazepine
Decreased carbamazepine effect (increased metabolism) Monitor carbamazepine and phenytoin concentrations
Altered phenytoin effect may include decreased or increased phenytoin levels (mechanism not established)
  • Clonazepam
Decreased clonazepam effect (increased metabolism) Monitor clinical status
  Monitor phenytoin concentrations
  • Eslicarbazepine
Decreased eslicarbazepine concentrations (increased metabolism) Monitor clinical status; eslicarbazepine dose may need to be increased
Possible phenytoin toxicity (decreased metabolism by CYP2C19) Monitor clinical status and phenytoin concentrations
  • Felbamate
Decreased felbamate effect (increased metabolism) Monitor felbamate effect; dose may need to be increased
Possible phenytoin toxicity (mechanism not established) Phenytoin dose reduction may be needed; refer to Lexicomp for detail. Monitor clinical status and phenytoin concentrations.
  • Lamotrigine
Decreased lamotrigine serum concentrations (increased metabolism; induction of glucuronidation by phenytoin) Monitor clinical status and lamotrigine serum concentrations; lamotrigine dose may need to be adjusted
  • Levetiracetam
Possible decreased levetiracetam concentrations (increased metabolism) Monitor clinical effect
  • Oxcarbazepine
Possible decreased oxcarbazepine effect (increased metabolism) Monitor clinical status and oxcarbazepine concentration
Possible phenytoin toxicity with oxcarbazepine doses of 1200 mg/day or higher (decreased metabolism by CYP2C19) Monitor phenytoin concentrations especially when oxcarbazepine dosage is 1200 mg/day or higher; reduction of phenytoin dose may be needed
  • Perampanel
Decreased perampanel effect (increased metabolism by CYP3A4) Monitor clinical status; perampanel dose may need to be adjusted
  • Tiagabine
Decreased tiagabine effect (increased metabolism by CYP3A4) Monitor clinical status
  • Topiramate
Possible decreased topiramate effect (increased metabolism) Monitor clinical status; may need to increase topiramate dose
Possible phenytoin toxicity (decreased metabolism by CYP2C19) with high doses of topiramate Monitor clinical status and phenytoin concentrations
  • Valproate
Possible phenytoin toxicity (displacement from binding and decreased metabolism, complex time course) Monitor clinical status and phenytoin concentrations (unbound concentrations may be more helpful than total)
Possible decreased valproate effect and increased toxicity (increased metabolism and formation of toxic metabolite) Monitor clinical status and valproate serum concentrations
  • Zonisamide
Decreased zonisamide effect (increased metabolism by CYP3A4) Monitor clinical status and zonisamide concentrations; zonisamide dose may need to be adjusted
The pharmacokinetics of phenytoin are distinctive in that its metabolism by CYP2C9 and 2C19 is saturable and half-life variable (ie, from 12 hours to up to 10 days or more) depending upon serum levels. The magnitude of effect due to a drug interaction can vary widely based upon phenytoin serum level, and a new steady-state phenytoin level may not occur until 2 to 3 weeks following an alteration of therapy. Refer to accompanying text.
CYP: cytochrome P450.
* Not all potential interactions are listed. Additional interactions of antiseizure medications and management suggestions may be determined using the drug interactions program included within UpToDate.
Data from: Lexicomp Online. Copyright © 1978-2024 Lexicomp, Inc. All Rights Reserved.
Graphic 55399 Version 19.0

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