Drug interactions
Promethazine + Secobarbital
Severity: Major
Promethazine and Secobarbital: major interaction.
Last updated Sources: US FDA label
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
Promethazine and the barbiturate secobarbital both depress the CNS, so the combination can cause profound sedation and respiratory depression. Barbiturates may also induce hepatic enzymes and alter drug levels.
What this interaction means in plain words
Promethazine and Secobarbital can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Promethazine belongs to Respiratory; Secobarbital belongs to Central Nervous System.
Why it happens
Additive CNS and respiratory depression from H1 antagonism and GABA-A potentiation.
What to do
Avoid the combination where possible, or reduce doses and monitor respiratory rate and level of consciousness. Warn patients against driving and alcohol.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
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References
Other interactions of Promethazine
- Ibutilide + Promethazine Contraindicated
- Pimozide + Promethazine Contraindicated
- Promethazine + Thioridazine Contraindicated
- Alfentanil + Promethazine Major
- Amiodarone + Promethazine Major
- Amisulpride + Promethazine Major
Other interactions of Secobarbital
- Calcium / magnesium / potassium / sodium oxybates + Secobarbital Contraindicated
- Doravirine + Secobarbital Contraindicated
- Elbasvir / grazoprevir + Secobarbital Contraindicated
- Elvitegravir / cobicistat / emtricitabine / tenofovir df + Secobarbital Contraindicated
- Isavuconazonium + Secobarbital Contraindicated
- Lonafarnib + Secobarbital Contraindicated
Frequently asked questions
Can I take Promethazine with Secobarbital?
MediHelp rates the interaction as major. Promethazine and Secobarbital can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Promethazine and the barbiturate secobarbital both depress the CNS, so the combination can cause profound sedation and respiratory depression. Barbiturates may also induce hepatic enzymes and alter drug levels.
How serious is the interaction between Promethazine and Secobarbital?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid the combination where possible, or reduce doses and monitor respiratory rate and level of consciousness. Warn patients against driving and alcohol.
What other medicines interact with Promethazine?
MediHelp also lists interactions of Promethazine with, for example, Ibutilide, Pimozide, Thioridazine. The full list is on the Promethazine page.
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