Diazepam and Promethazine interaction

Diazepam and Promethazine: both prescribing labels describe an interaction that usually calls for monitoring, a dose change, or spacing the doses.

Moderate

Usually manageable with monitoring or a dose change. Tell your pharmacist you take both.

What the FDA labels say

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

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

From the Promethazine (PROMETHAZINE HYDROCHLORIDE) label · effective 2026-04-16

Moderate

The impairment may be amplified by concomitant use of other central-nervous-system depressants such as alcohol, sedatives/hypnotics (including barbiturates), narcotics, narcotic analgesics, general anesthetics, tricyclic antidepressants, and tranquilizers; therefore such agents should either be eliminated or given in reduced dosage in the presence of promethazine…

Warningsby drug classView label on DailyMed
Moderate

Drug Interactions CNS Depressants Promethazine Syrup may increase, prolong, or intensify the sedative action of other central-nervous-system depressants, such as alcohol, sedatives/hypnotics (including barbiturates), narcotics, narcotic analgesics, general anesthetics, tricyclic antidepressants, and tranquilizers; therefore, such agents should be avoided or administered…

Drug interactionsby drug classView label on DailyMed
Moderate

CNS Depressants Promethazine Syrup may increase, prolong, or intensify the sedative action of other central-nervous-system depressants, such as alcohol, sedatives/hypnotics (including barbiturates), narcotics, narcotic analgesics, general anesthetics, tricyclic antidepressants, and tranquilizers; therefore, such agents should be avoided or administered in reduced…

Drug interactionsby drug classView label on DailyMed

Taking more than these two? Interactions stack. Check your whole list at once; it stays in your browser.

Open in the checker

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.