Drug interactions
Methohexital + Promethazine
Severity: Major
Methohexital and Promethazine: 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
Methohexital is a short-acting barbiturate anesthetic, and promethazine is a sedating antihistamine. Together they produce additive CNS and respiratory depression and may cause hypotension. Recovery from anesthesia may be prolonged.
What this interaction means in plain words
Methohexital and Promethazine 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.
Methohexital belongs to Central Nervous System; Promethazine belongs to Respiratory.
Why it happens
Additive CNS depression via GABA-A potentiation by the barbiturate and H1 antagonism with sedative phenothiazine effects.
What to do
Reduce the methohexital dose as needed and provide continuous monitoring of oxygenation, ventilation and blood pressure. Ensure airway support is available.
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?
Pro+ members
Unlock the full page
Create an account and start a Pro+ trial to unlock the full management advice for Methohexital and Promethazine, the additional notes, the evidence detail and the whole-prescription interaction checker.
- Full clinical management advice
- Additional notes
- Evidence detail
- Interaction checker for a whole prescription
Try Pro+ free for 7 days on the web. No card needed.
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 Methohexital
Frequently asked questions
Can I take Methohexital with Promethazine?
MediHelp rates the interaction as major. Methohexital and Promethazine 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. Methohexital is a short-acting barbiturate anesthetic, and promethazine is a sedating antihistamine. Together they produce additive CNS and respiratory depression and may cause hypotension. Recovery from anesthesia may be prolonged.
How serious is the interaction between Methohexital and Promethazine?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Reduce the methohexital dose as needed and provide continuous monitoring of oxygenation, ventilation and blood pressure. Ensure airway support is available.
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.
Full monographs, dosing and an interaction checker in the MediHelp app
Open the complete reference, check multi-drug interactions and use dosing tools in the MediHelp app.
