Diazepam and Phenytoin interaction

Diazepam and Phenytoin: both prescribing labels flag this combination with the strongest language, such as a contraindication, a boxed warning, or an instruction to avoid it.

Major

Do not combine without a prescriber's guidance. The label language below is the strongest FDA uses.

What the FDA labels say

From the Phenytoin label · effective 2024-12-24

Major

…Phenytoin and antacids should not be taken at the same time of day Antineoplastic agents (usually in combination) Bleomycin, carboplatin, cisplatin, doxorubicin, methotrexate Antiviral agents Fosamprenavir, nelfinavir, ritonavir Antiepileptic drugs Carbamazepine, vigabatrin Other Chronic alcohol abuse, diazepam, diazoxide, folic acid, reserpine, rifampin, St.

Drug interactionsnames DiazepamView label on DailyMed

From the Diazepam (Valium) label · effective 2026-08-11

Moderate

Phenytoin There have also been reports that the metabolic elimination of phenytoin is decreased by diazepam.

Drug interactionsnames PhenytoinView label on DailyMed
Moderate

As with other agents that have anticonvulsant activity, when Valium is used as an adjunct in treating convulsive disorders, the possibility of an increase in the frequency and/or severity of grand mal seizures may require an increase in the dosage of standard anticonvulsant medication.

Warningsby drug classView label on DailyMed
Moderate

…be given to the pharmacology of the agents employed particularly with compounds that may potentiate or be potentiated by the action of Valium, such as phenothiazines, antipsychotics, anxiolytics/sedatives, hypnotics, anticonvulsants, narcotic analgesics, anesthetics, sedative antihistamines, narcotics, barbiturates, MAO inhibitors and other antidepressants.

Drug interactionsby drug classView label on DailyMed
Minor

Since Valium has a central nervous system depressant effect, patients should be advised against the simultaneous ingestion of alcohol and other CNS- depressant drugs during Valium therapy.

Warningsby drug classView label on DailyMed
Minor

Patients should be advised against the simultaneous ingestion of alcohol and other CNS-depressant drugs during Valium therapy.

Precautionsby drug classView label on DailyMed

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Not medical advice. Interaction Checker quotes FDA label text and NIH fact sheets. Whether an interaction matters for you depends on doses, timing, kidney and liver function, and other conditions. Confirm with a pharmacist or prescriber.