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Drug Interactions between fosphenytoin and modafinil

This report displays the potential drug interactions for the following 2 drugs:

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Interactions between your drugs

Moderate

fosphenytoin modafinil

Applies to: fosphenytoin and modafinil

MONITOR: Coadministration with modafinil (the racemate) or armodafinil (the R-enantiomer) may increase the plasma concentrations of phenytoin. The proposed mechanism is decreased clearance due to inhibition of CYP450 2C19 activity by modafinil and armodafinil. In pharmacokinetic studies, coadministration of a single 400 mg dose of armodafinil with omeprazole 40 mg, a CYP450 2C19 substrate, increased systemic exposure to omeprazole by approximately 40%. Conversely, phenytoin, a potent inducer of CYP450 3A4, may decrease the plasma levels of modafinil or armodafinil, which are both partially metabolized by the isoenzyme.

MANAGEMENT: Caution is advised if modafinil or armodafinil must be used concurrently with phenytoin. Pharmacologic response to modafinil or armodafinil should be monitored more closely and patients should be monitored for signs of phenytoin toxicity. Dosage adjustments as well as clinical and laboratory monitoring may be appropriate whenever these drugs are added to or withdrawn from therapy.

References (6)
  1. Robertson P, Decory HH, Madan A, Parkinson A (2000) "In vitro inhibition and induction of human hepatic cytochrome P450 enzymes by modafinil." Drug Metab Dispos, 28, p. 664-71
  2. (2007) "Product Information. Nuvigil (armodafinil)." Cephalon Inc
  3. (2024) "Product Information. Modafinil (modafinil)." Milpharm Ltd
  4. (2023) "Product Information. Modafinil (Apo) (modafinil)." Apotex Pty Ltd
  5. (2024) "Product Information. Apo-Modafinil (modafinil)." Apotex Incorporated
  6. (2024) "Product Information. Modafinil (modafinil)." Heritage Pharmaceuticals Inc

Drug and food interactions

Minor

modafinil food

Applies to: modafinil

Administration with food may delay the absorption of modafinil (the racemate) and armodafinil (the R-enantiomer) without significantly affecting their overall bioavailability. According to the product labeling, modafinil's absorption may be delayed by approximately one hour if taken with food. Similarly, the time to reach peak plasma concentration (Tmax) of armodafinil may be delayed by approximately 2 to 4 hours in the fed state.

References (2)
  1. (2001) "Product Information. Provigil (modafinil)." Cephalon, Inc
  2. (2007) "Product Information. Nuvigil (armodafinil)." Cephalon Inc

Therapeutic duplication warnings

No warnings were found for your selected drugs.

Therapeutic duplication warnings are only returned when drugs within the same group exceed the recommended therapeutic duplication maximum.

See also

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Drug Interaction Classification

These classifications are only a guideline. The relevance of a particular drug interaction to a specific individual is difficult to determine. Always consult your healthcare provider before starting or stopping any medication.
Major Highly clinically significant. Avoid combinations; the risk of the interaction outweighs the benefit.
Moderate Moderately clinically significant. Usually avoid combinations; use it only under special circumstances.
Minor Minimally clinically significant. Minimize risk; assess risk and consider an alternative drug, take steps to circumvent the interaction risk and/or institute a monitoring plan.
Unknown No interaction information available.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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