Drug interactions
Pentazocine + Phenobarbital
Severity: Major
Pentazocine and Phenobarbital: major interaction.
Last updated
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 combined with an opioid can cause deep sedation, respiratory depression, coma and death. Phenobarbital also induces hepatic enzymes, which may alter the exposure of pentazocine over time.
What this interaction means in plain words
Pentazocine 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 central nervous system and respiratory depression; phenobarbital additionally induces hepatic metabolism.
What to do
Avoid if possible, or use the lowest effective doses and monitor respiratory rate and sedation closely. Reassess analgesic response because enzyme induction may reduce pentazocine effect.
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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Other interactions of Pentazocine
- Calcium / magnesium / potassium / sodium oxybates + Pentazocine Contraindicated
- Olanzapine / samidorphan + Pentazocine Contraindicated
- Pentazocine + Phenelzine Contraindicated
- Pentazocine + Tranylcypromine Contraindicated
- Alfentanil + Pentazocine Major
- Alprazolam + Pentazocine Major
Frequently asked questions
Can I take Pentazocine with Phenobarbital?
MediHelp rates the interaction as major. Pentazocine 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 combined with an opioid can cause deep sedation, respiratory depression, coma and death. Phenobarbital also induces hepatic enzymes, which may alter the exposure of pentazocine over time.
How serious is the interaction between Pentazocine 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: Avoid if possible, or use the lowest effective doses and monitor respiratory rate and sedation closely. Reassess analgesic response because enzyme induction may reduce pentazocine effect.
What other medicines interact with Pentazocine?
MediHelp also lists interactions of Pentazocine with, for example, Calcium / magnesium / potassium / sodium oxybates, Olanzapine / samidorphan, Phenelzine. The full list is on the Pentazocine page.
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