Phenobarbital and Colchicine: Interaction Details
AI-assisted, pharmacist-reviewed · AI content regenerated Jul 11, 2026 · Source data updated Jul 2, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Phenobarbital
Colchicine
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
You've been prescribed phenobarbital and colchicine together, so let's talk about how they interact. Phenobarbital speeds up an enzyme in your liver (called CYP3A) that breaks down colchicine. When colchicine gets cleared out faster, there may be less of it in your body, which could make it less effective at doing its job (for example, controlling gout flares).
I want to be clear that this is based on how these drugs work in theory, not strong real-world proof. The good news is your care team can handle this easily by watching how well your colchicine is working and adjusting your dose if needed. Please don't change anything on your own, just check in with your doctor or pharmacist.
Mechanism: Phenobarbital is a CYP3A4 inducer; colchicine is a CYP3A4 (and P-gp) substrate. Induction increases colchicine metabolism, lowering its plasma exposure (reduced AUC/Cmax) and potentially reducing efficacy.
Direction: Reduced colchicine effect (neither drug is a prodrug here).
- Severity: Major
- Onset: Unspecified (enzyme induction is typically delayed, days to weeks)
- Evidence: Theoretical
Management: Monitor clinical response to colchicine (e.g., gout flare control). If coadministration is unavoidable, the colchicine dose may need to be increased and individualized. In neonatal use, monitor closely.
What happens
Reduced CYP3A substrate exposure and reduced efficacy of CYP3A substrate
Interaction Deep Dive
When PHENobarbital, which induces CYP3A, is taken together with a CYP3A substrate, the exposure to that substrate can fall, potentially lowering its therapeutic effect. Where such combined use is unavoidable, neonates should be watched carefully and raising the dose of the CYP3A substrate as needed should be considered1.
Why it happens (mechanism)
Induction of CYP3A-mediated metabolism of CYP3A substrates
How to manage this interaction
Here's how your care team typically handles this combination:
- Keep taking both exactly as prescribed unless your doctor tells you otherwise.
- Your team may monitor how well the colchicine is working (for example, whether your gout symptoms stay controlled).
- Because phenobarbital can lower colchicine levels, your colchicine dose may need to be adjusted and individualized by your prescriber.
- If a baby or newborn is involved, closer monitoring is standard.
What to do: Tell your pharmacist or prescriber that you take both, and mention it if your colchicine doesn't seem to be working as well as before.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Phenobarbital and Colchicine together?
Phenobarbital can speed up how your body clears colchicine, which may make the colchicine work less well; your care team can manage this by monitoring your response and adjusting the colchicine dose if needed. Keep taking both as prescribed and check in with your pharmacist or doctor. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Phenobarbital and Colchicine interaction?
It is rated major. Potentially serious — often needs a change or close monitoring.
How quickly could this interaction happen?
The documented onset is "unspecified". The timing of this interaction is not well characterized.
How is the Phenobarbital and Colchicine interaction managed?
Here's how your care team typically handles this combination: Keep taking both exactly as prescribed unless your doctor tells you otherwise. Your team may monitor how well the colchicine is working (for example, whether your gout symptoms stay controlled). Because phenobarbital can lower colchicine levels, your colchicine dose may need to be adjusted and individualized by your prescriber. If a bab… Management is individual — always follow your own care team's guidance.
How strong is the evidence for this interaction?
The evidence is graded "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
Questions for your pharmacist
- Does my dose of Phenobarbital or Colchicine need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there a safer alternative to one of these medications for me?
References (1)
- Product Information: SEZABY(TM) intravenous injection, phenobarbital sodium intravenous injection. Sun Pharmaceutical Industries Inc (per manufacturer), Cranbury, NJ, 2022. DailyMed
Keep reading about Phenobarbital
Keep reading about Colchicine
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