Diltiazem 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
Diltiazem
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.
Diltiazem (a blood pressure and heart medicine) can cause colchicine (used for gout) to build up in your body. Diltiazem slows down the systems that normally break colchicine down and push it out of your cells, so more colchicine stays behind.
That matters because too much colchicine can be very dangerous, even life-threatening. Watch for warning signs like severe diarrhea, vomiting, stomach pain, muscle weakness, or unusual tiredness. Please don't stop or change either medicine on your own. Talk with your pharmacist or doctor. They can safely lower your colchicine dose or take other steps to protect you, and this is very manageable when your care team knows you take both.
Effect: Diltiazem inhibits both CYP3A4-mediated metabolism and P-gp-mediated efflux of colchicine, increasing colchicine exposure and the risk of serious or fatal toxicity (neuromyopathy, bone marrow suppression, multi-organ failure). Colchicine is the affected substrate; neither drug is a prodrug, so exposure rises.
- Severity: Contraindicated with dual inhibitors, especially in renal or hepatic impairment.
- Evidence: Probable; onset unspecified.
- Management: Avoid in renal/hepatic impairment. If coadministration is necessary in patients with normal organ function, reduce colchicine daily dose by 50% to 75% or decrease dosing frequency, and monitor for toxicity.
What happens
Increased colchicine exposure and an increased risk of fatal toxicity
Interaction Deep Dive
Colchicine must not be given together with P-gp inhibitors1. When colchicine is combined with agents that inhibit both CYP3A4 and P-gp, there is a risk of severe, potentially fatal toxicity. Should coadministration of colchicine and a P-gp inhibitor become unavoidable, the colchicine dose ought to be modified, either by cutting the daily amount by 50% to 75% 3 or by decreasing how often it is taken. Furthermore, in patients who have renal or hepatic impairment, colchicine is contraindicated alongside P-gp and CYP3A4 inhibitors 3. In such patients with renal and hepatic impairment, the use of these inhibitors together with colchicine has produced life-threatening or fatal colchicine toxicity 2.
Why it happens (mechanism)
Inhibition of P-gp-mediated efflux transport of colchicine; inhibition of CYP3A4-mediated metabolism of colchicine
How to manage this interaction
This combination is taken seriously because diltiazem can make colchicine levels rise. The good news is your care team has clear ways to handle it.
- Keep taking both exactly as prescribed unless your doctor or pharmacist tells you otherwise.
- Your team may lower your colchicine dose (often by half or more) or space out the doses, and may monitor you more closely.
- This combination is generally avoided entirely if you have kidney or liver problems, so make sure your team knows your full history.
- Call your pharmacist or prescriber right away if you have severe diarrhea, vomiting, muscle weakness, or numbness/tingling.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Diltiazem and Colchicine together?
Diltiazem raises colchicine levels and can cause dangerous toxicity, so this combo is contraindicated, especially with kidney or liver problems. Don't stop either drug on your own, but contact your pharmacist or doctor promptly so they can adjust your colchicine dose or choose a safer plan. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Diltiazem and Colchicine interaction?
It is rated contraindicated. These should generally not be used together.
How quickly could this interaction happen?
The documented onset is "unspecified". The timing of this interaction is not well characterized.
How is the Diltiazem and Colchicine interaction managed?
This combination is taken seriously because diltiazem can make colchicine levels rise. The good news is your care team has clear ways to handle it. Keep taking both exactly as prescribed unless your doctor or pharmacist tells you otherwise. Your team may lower your colchicine dose (often by half or more) or space out the doses, and may monitor you more closely. This combination is generally avoide… Management is individual — always follow your own care team's guidance.
How strong is the evidence for this interaction?
The evidence is graded "probable". Good supporting evidence, though not definitively proven.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Diltiazem 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 (3)
- Product Information: LODOCO(R) oral tablets, colchicine oral tablets. AGEPHA Pharma USA, LLC (per FDA), Parsippany, NJ, 2023. DailyMed
- Product Information: MITIGARE(R) oral capsules, colchicine oral capsules. Hikma Specialty USA Inc (per FDA), Columbus, OH, 2024. DailyMed
- Hansten PD, Tan MS, Horn JR, et al: Colchicine drug interaction errors and misunderstandings: recommendations for improved evidence-based management. Drug Saf 2023; 46(3):223-242. PubMed
Keep reading about Diltiazem
Keep reading about Colchicine
These medications also interact with supplements
Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:
major · moderate · minor — check everything you take with our drug–supplement interaction checker.
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