Drug interactions
Clorazepate + Fosphenytoin
Severity: Moderate
Clorazepate and Fosphenytoin: moderate interaction.
Last updated
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Fosphenytoin is converted to phenytoin, an inducer of CYP3A4 and other enzymes, which can increase clearance of the active metabolite of clorazepate and reduce its effect. Seizure control or anxiolytic benefit may diminish, and benzodiazepines may also alter phenytoin levels unpredictably.
What this interaction means in plain words
Clorazepate and Fosphenytoin can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Clorazepate belongs to Central Nervous System; Fosphenytoin belongs to Central Nervous System.
Why it happens
Phenytoin-mediated induction of hepatic CYP3A4 increases metabolism of nordiazepam, the active metabolite of clorazepate.
What to do
Monitor clinical response and seizure control, and increase the clorazepate dose if efficacy is lost. Check phenytoin concentrations when therapy is started or stopped.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
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Other interactions of Clorazepate
- Calcium / magnesium / potassium / sodium oxybates + Clorazepate Contraindicated
- Clorazepate + Sodium oxybate Contraindicated
- Alfentanil + Clorazepate Major
- Alprazolam + Clorazepate Major
- Amobarbital + Clorazepate Major
- Belladonna and opium + Clorazepate Major
Other interactions of Fosphenytoin
- Dronedarone + Fosphenytoin Contraindicated
- Fosphenytoin + Ledipasvir-sofosbuvir Contraindicated
- Fosphenytoin + Lorlatinib Contraindicated
- Fosphenytoin + Lurasidone Contraindicated
- Fosphenytoin + Ranolazine Contraindicated
- Fosphenytoin + Sofosbuvir-velpatasvir-voxilaprevir Contraindicated
Frequently asked questions
Can I take Clorazepate with Fosphenytoin?
MediHelp rates the interaction as moderate. Clorazepate and Fosphenytoin can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Fosphenytoin is converted to phenytoin, an inducer of CYP3A4 and other enzymes, which can increase clearance of the active metabolite of clorazepate and reduce its effect. Seizure control or anxiolytic benefit may diminish, and benzodiazepines may also alter phenytoin levels unpredictably.
How serious is the interaction between Clorazepate and Fosphenytoin?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor clinical response and seizure control, and increase the clorazepate dose if efficacy is lost. Check phenytoin concentrations when therapy is started or stopped.
What other medicines interact with Clorazepate?
MediHelp also lists interactions of Clorazepate with, for example, Calcium / magnesium / potassium / sodium oxybates, Sodium oxybate, Alfentanil. The full list is on the Clorazepate page.
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