Drug interactions
Chlordiazepoxide + Fosphenytoin
Severity: Moderate
Chlordiazepoxide 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 enzyme inducer that can lower chlordiazepoxide concentrations and reduce its effect. Benzodiazepines can also alter phenytoin levels unpredictably, so both anxiolytic and anticonvulsant control may be affected.
What this interaction means in plain words
Chlordiazepoxide 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.
Chlordiazepoxide belongs to Central Nervous System; Fosphenytoin belongs to Central Nervous System.
Why it happens
Phenytoin induces CYP3A4 and other hepatic enzymes, increasing chlordiazepoxide metabolism; benzodiazepines may also variably change phenytoin levels.
What to do
Monitor clinical response to chlordiazepoxide and adjust the dose as needed. Check phenytoin concentrations when starting or stopping the benzodiazepine.
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 Chlordiazepoxide
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 Chlordiazepoxide with Fosphenytoin?
MediHelp rates the interaction as moderate. Chlordiazepoxide 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 enzyme inducer that can lower chlordiazepoxide concentrations and reduce its effect. Benzodiazepines can also alter phenytoin levels unpredictably, so both anxiolytic and anticonvulsant control may be affected.
How serious is the interaction between Chlordiazepoxide 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 to chlordiazepoxide and adjust the dose as needed. Check phenytoin concentrations when starting or stopping the benzodiazepine.
What other medicines interact with Chlordiazepoxide?
MediHelp also lists interactions of Chlordiazepoxide with, for example, Alfentanil, Alprazolam, Amobarbital. The full list is on the Chlordiazepoxide page.
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