Drug interactions
Paracetamol + Phenobarbital
Severity: Moderate
Paracetamol and Phenobarbital: moderate 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 induces hepatic enzymes, which can reduce paracetamol levels and increase production of the hepatotoxic metabolite NAPQI. This raises the risk of liver injury, especially with high doses or overdose.
What this interaction means in plain words
Paracetamol and Phenobarbital can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Why it happens
Induction of CYP enzymes and glucuronidation increases oxidative paracetamol metabolism to NAPQI.
What to do
Avoid chronic high-dose paracetamol in patients on phenobarbital and keep to the lowest effective dose. Monitor liver function with prolonged use and treat overdose early with acetylcysteine.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
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Other interactions of Paracetamol
- Ethanol + Paracetamol Major
- Busulfan + Paracetamol Moderate
- Carbamazepine + Paracetamol Moderate
- Cholestyramine + Paracetamol Moderate
- Felbamate + Paracetamol Moderate
- Fosphenytoin + Paracetamol Moderate
Frequently asked questions
Can I take Paracetamol with Phenobarbital?
MediHelp rates the interaction as moderate. Paracetamol and Phenobarbital can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Phenobarbital induces hepatic enzymes, which can reduce paracetamol levels and increase production of the hepatotoxic metabolite NAPQI. This raises the risk of liver injury, especially with high doses or overdose.
How serious is the interaction between Paracetamol and Phenobarbital?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid chronic high-dose paracetamol in patients on phenobarbital and keep to the lowest effective dose. Monitor liver function with prolonged use and treat overdose early with acetylcysteine.
What other medicines interact with Paracetamol?
MediHelp also lists interactions of Paracetamol with, for example, Ethanol, Busulfan, Carbamazepine. The full list is on the Paracetamol page.
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