Drug interactions
Lorazepam + Phenobarbital
Severity: Major
Lorazepam and Phenobarbital: 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
Phenobarbital and lorazepam together cause additive sedation and respiratory depression. Phenobarbital may also induce hepatic enzymes, though lorazepam is cleared mainly by glucuronidation so this effect is modest.
What this interaction means in plain words
Lorazepam and Phenobarbital 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.
Why it happens
Additive GABA-A mediated CNS depression, with possible modest enzyme induction by phenobarbital.
What to do
Monitor sedation, respiratory status and blood pressure, and use the lowest effective doses. Take special care in older, frail or respiratory-compromised patients.
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 Lorazepam
Frequently asked questions
Can I take Lorazepam with Phenobarbital?
MediHelp rates the interaction as major. Lorazepam and Phenobarbital 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. Phenobarbital and lorazepam together cause additive sedation and respiratory depression. Phenobarbital may also induce hepatic enzymes, though lorazepam is cleared mainly by glucuronidation so this effect is modest.
How serious is the interaction between Lorazepam and Phenobarbital?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor sedation, respiratory status and blood pressure, and use the lowest effective doses. Take special care in older, frail or respiratory-compromised patients.
What other medicines interact with Lorazepam?
MediHelp also lists interactions of Lorazepam with, for example, Alfentanil, Alprazolam, Amobarbital. The full list is on the Lorazepam page.
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