Atazanavir 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
Atazanavir
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.
Atazanavir (Reyataz) can cause colchicine to build up in your body. Atazanavir slows down the liver enzyme (called CYP3A4) that normally breaks colchicine down. When colchicine can't be cleared, its levels climb, and colchicine has a narrow safety window. Too much can cause serious problems like severe diarrhea, muscle weakness, and dangerous effects on the blood and other organs. In some people this combination has even been life-threatening.
The good news is your care team can manage this. Please don't stop either medicine on your own. Talk with your pharmacist or doctor, who may lower your colchicine dose or choose a safer plan based on your kidney and liver health.
Mechanism: Atazanavir is a strong CYP3A4 inhibitor (and P-gp inhibitor); colchicine is a CYP3A4/P-gp substrate. Inhibition reduces colchicine clearance, increasing exposure and risk of toxicity.
- Direction: Increased colchicine AUC/Cmax, increased toxicity risk (neuromyopathy, GI toxicity, myelosuppression, multiorgan failure).
- Evidence: Theoretical for atazanavir specifically; extrapolated from documented fatal toxicity with clarithromycin.
- Management: Contraindicated in renal or hepatic impairment. In normal renal/hepatic function, dose-reduce colchicine (e.g., gout flare: 0.6 mg once, then 0.3 mg 1 h later, no repeat course sooner than 3 days; prophylaxis and FMF per labeling). Applies for 14 days after the inhibitor.
What happens
Increased colchicine exposure and an increased risk of colchicine toxicity
Interaction Deep Dive
Taking colchicine together with a strong CYP3A4 inhibitor is contraindicated, since colchicine toxicity that is both life-threatening and fatal has been documented in such patients even when colchicine is dosed within the therapeutic range1. Colchicine serves as a substrate for both CYP3A4 and P-glycoprotein (P-gp). When colchicine was combined with clarithromycin, a strong inhibitor of CYP3A4 and P-gp, colchicine exposure rose substantially and fatal toxicity ensued. Toxicity has likewise been seen when colchicine was given alongside a CYP3A4 inhibitor and when it was given alongside a P-gp inhibitor3. For patients with renal or hepatic impairment, coadministration of colchicine with a strong CYP3A4 inhibitor (which includes every protease inhibitor other than fosamprenavir) is contraindicated. In patients whose renal and hepatic function is normal and who are currently receiving, or who have received within the previous 14 days, a strong CYP3A4 inhibitor, the colchicine dose must be modified. When treating a gout flare, lower the colchicine dose to a single 0.6 mg tablet, followed 1 hour later by 0.3 mg (half a tablet), with the next dose given no sooner than 3 days afterward. For gout flare prophylaxis, cut the colchicine dose from 0.6 mg twice daily down to 0.3 mg once daily, or from 0.6 mg once daily down to 0.3 mg every other day. When treating familial Mediterranean fever, the colchicine dose should not exceed 0.6 mg per day (which may be administered as 0.3 mg twice daily)2.
Why it happens (mechanism)
Inhibition of CYP3A4-mediated colchicine metabolism by atazanavir
How to manage this interaction
Keep taking both medicines as prescribed until your care team advises otherwise, but raise this combination with your pharmacist or prescriber promptly.
- If you have kidney or liver problems, this pairing is generally not used together, so your team may choose a different option.
- If your kidney and liver function are normal, your colchicine dose will likely be lowered and individualized by your care team.
- This dose adjustment also applies if you've taken atazanavir within the past 14 days.
- Report any severe diarrhea, vomiting, muscle pain or weakness, numbness, or unusual tiredness right away.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) While the interaction involving atazanavir, a potent CYP3A4 inhibitor, and colchicine has not been formally examined, an interaction between colchicine and clarithromycin, which is another potent CYP3A4 inhibitor, led to fatal colchicine toxicity. When a single 0.6 mg dose of colchicine was given to patients (n=23) who had been receiving clarithromycin 250 mg twice daily for 7 days, colchicine Cmax and AUC rose by 227.2% and 281.5%, respectively 2.
Common questions
Can I take Atazanavir and Colchicine together?
Atazanavir can raise colchicine to toxic levels; do not combine at usual doses. Your care team will either avoid the combination (especially with kidney or liver problems) or reduce and individualize your colchicine dose. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Atazanavir 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 Atazanavir and Colchicine interaction managed?
Keep taking both medicines as prescribed until your care team advises otherwise, but raise this combination with your pharmacist or prescriber promptly. If you have kidney or liver problems, this pairing is generally not used together, so your team may choose a different option. If your kidney and liver function are normal, your colchicine dose will likely be lowered and individualized by your car… 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 Atazanavir 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 (4)
- Product Information: LODOCO(R) oral tablets, colchicine oral tablets. AGEPHA Pharma USA, LLC (per FDA), Parsippany, NJ, 2023. DailyMed
- Product Information: COLCRYS oral tablets, colchicine oral tablets. Takeda Pharmaceuticals America Inc (per FDA), Deerfield, IL, 2020. DailyMed
- Product Information: GLOPERBA(R) oral solution, colchicine oral solution. Romeg Therapeutics LLC (per FDA), Woburn, MA, 2019. DailyMed
- Product Information: REYATAZ(R) oral capsules, atazanavir sulfate oral capsules. Bristol-Myers Squibb Company, Princeton, NJ, 2010. DailyMed
Keep reading about Atazanavir
Keep reading about Colchicine
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