Drug interactions between phenytoin and Seroquel
Results for the following 2 drugs: |
|
|---|---|
| phenytoin | |
| Seroquel (quetiapine) | |
Interactions between your selected drugs
phenytoin ⇔ quetiapine
Applies to: phenytoin and Seroquel (quetiapine)
MONITOR: Coadministration with phenytoin may decrease the plasma concentrations of quetiapine. The mechanism is phenytoin induction of CYP450 3A4, the isoenzyme responsible for the metabolic clearance of quetiapine. In ten subjects with various affective disorders, phenytoin (100 mg orally three times a day) decreased the mean steady-state peak plasma concentration (Cmax), trough plasma concentration (Cmin) and area under the concentration-time curve (AUC) of quetiapine (250 mg orally three times a day) by 66%, 89% and 80%, respectively, compared to administration of quetiapine alone. The mean oral clearance increased by 5.5-fold with phenytoin. Fosphenytoin is also expected to cause this interaction if used for more than 2 or 3 days, since it is rapidly metabolized in vivo to phenytoin.
MANAGEMENT: Patients treated concomitantly with phenytoin may require a higher dosage of quetiapine to control psychotic symptoms. Pharmacologic response to quetiapine should be monitored more closely whenever phenytoin is added to or withdrawn from therapy in patients stabilized on their existing antipsychotic regimen, and the quetiapine dosage adjusted as necessary.
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