Trial Snapshot
You just survived a heart attack. You're on aspirin, a statin, a P2Y12 inhibitor. Is that enough? COLCOT asked whether adding an anti-inflammatory on top of that guideline therapy lowers recurrent risk.
| Published | 2019, NEJM |
| Patients | 4,745 |
| Sites | 167 |
| Follow-up | Median 22.6 months |
| Design | Randomized, double-blind, placebo-controlled |
| Population | MI within the prior 30 days, on guideline-directed medical therapy |
| Intervention | Colchicine 0.5 mg once daily vs placebo |
The clinical question: does colchicine 0.5 mg/day, started within 30 days of MI, reduce recurrent cardiovascular events on top of standard post-MI therapy?
Primary Endpoint
The primary endpoint was a composite: cardiovascular death, resuscitated cardiac arrest, MI, stroke, or urgent hospitalization for angina leading to revascularization.
HR 0.77 (95% CI 0.61 to 0.96), P=0.02
Absolute risk reduction: 1.6 percentage points
NNT of about 63 comes directly from the 1.6% absolute risk reduction (1 divided by 0.016).
What Moved, What Didn't
The benefit was not spread evenly across the five components of the composite. Two endpoints carried the entire result.
| Component | Hazard ratio | Significant? |
|---|---|---|
| Cardiovascular death | 0.84 (0.46 to 1.52) | No |
| Resuscitated cardiac arrest | 0.83 (0.25 to 2.73) | No |
| MI | 0.91 (0.68 to 1.21) | No |
| Stroke | 0.26 (0.10 to 0.70) | Yes |
| Urgent hospitalization for angina with revascularization | 0.50 (0.31 to 0.81) | Yes |
Stroke and urgent revascularization for angina were the only two components that individually reached significance. CV death and MI, the outcomes clinicians usually care about most, did not move on their own.
The Stroke Signal, Read Carefully
A 74 percent relative risk reduction in stroke was COLCOT's most striking individual finding. It is also the one that deserves the most caution.
Stroke occurred in roughly 0.2% of the colchicine group versus 0.8% of placebo, HR 0.26 (95% CI 0.10 to 0.70).
That confidence interval is wide because the absolute event count is small: on the order of 25 to 30 total stroke events across all 4,745 patients over 22.6 months.
A wide confidence interval built on a handful of events can reflect either a real biological effect or the most dramatic-looking number a rare-event analysis can produce. LoDoCo2, a larger and longer trial in stable coronary disease (Section 9), did not specifically replicate a stroke signal of this size. Treat the point estimate as hypothesis-generating rather than settled.
Timing Matters
A prespecified time-to-treatment-initiation analysis, published separately in the European Heart Journal, split patients by how soon after MI they started colchicine: under 3 days, 4 to 7 days, or 8 to 30 days.
| Start time after MI | Relative risk reduction | Significant? |
|---|---|---|
| Within 3 days | 48% (HR 0.52, 95% CI 0.32 to 0.84) | Yes |
| 4 to 7 days | 4% | No |
| 8 to 30 days | 23% | No |
Earlier is better, and the effect does not fade gradually. It drops sharply after day 3. Start it in-hospital or the benefit is far less certain.
Safety
| Event | Colchicine | Placebo | P value |
|---|---|---|---|
| Diarrhea | 9.7% | 8.9% | 0.35 (not significant) |
| Nausea | 1.8% | 1.0% | Not reported as significant |
| Infection (serious AE) | 2.2% | 1.6% | Not reported as significant |
| Pneumonia (serious AE) | 0.9% | 0.4% | 0.03, only significant safety signal |
Cancer incidence (excluding nonmelanoma skin cancer) was essentially identical between arms: 1.8% colchicine versus 1.9% placebo.
Mechanism
Binds tubulin, which blocks neutrophil migration to sites of vascular injury
Inhibits the NLRP3 inflammasome, reducing downstream IL-1β and IL-18 release
Net effect: dampened leukocyte-driven inflammation at the site of atherosclerotic plaque, theorized to stabilize plaque and blunt the inflammatory cascade that follows MI
Colchicine's anti-inflammatory action here is broad and non-selective, unlike a targeted agent such as the IL-1β antibody canakinumab, which showed a related but more expensive signal in CANTOS.
Where This Sits in Guidelines
The 2023 ESC guidelines for acute coronary syndromes give low-dose colchicine (0.5 mg once daily) a Class IIb recommendation: it may be considered, particularly when other risk factors are insufficiently controlled or events recur. That is a genuine guideline foothold, not just a trial result sitting in a journal.
Worth knowing: in the 2024 ESC chronic coronary syndromes guideline, colchicine's recommendation was actually downgraded from Class IIa to Class IIb, despite no new data arguing against it. That downgrade reflects the field's caution around the LoDoCo2 mortality signal (Section 9) more than any new failure of efficacy.
Related Trials, for Context
COLCOT is one piece of a larger colchicine cardiology story. Reading it next to LoDoCo2 changes how confidently you should hold the stroke and mortality claims.
| Trial | Population | N | Primary result |
|---|---|---|---|
| COLCOT (2019) | Recent MI, within 30 days | 4,745 | 5.5% vs 7.1%, HR 0.77 |
| LoDoCo2 (2020) | Chronic coronary disease | 5,522 | 6.8% vs 9.6%, HR 0.69 |
The caveat LoDoCo2 adds: despite the strong cardiovascular benefit, LoDoCo2 recorded a numerically higher noncardiovascular death rate with colchicine, HR 1.51 (95% CI 0.99 to 2.31), and a higher all-cause death rate, HR 1.21 (95% CI 0.86 to 1.71). Neither reached statistical significance, but neither trial was individually powered to rule the possibility out. Watch this space rather than treating colchicine as risk-free.
Quick Reference Card & Primary Sources
Clinical verdict: colchicine 0.5 mg/day is guideline-endorsed (ESC Class IIb) after MI. Start in-hospital, within 3 days if possible. An old gout drug that earned a genuine, if modest, modern cardiology indication, at roughly $0.10/day generic.
| Question | Answer |
|---|---|
| Reduces the composite endpoint? | Yes, HR 0.77, driven by stroke and urgent revascularization |
| Reduces CV death or MI alone? | No, neither reached significance individually |
| Best time to start? | Within 3 days of MI, in-hospital |
| Main safety signal? | Pneumonia, 0.9% vs 0.4% |
| Guideline status? | ESC Class IIb, 2023 ACS guideline |
Primary sources checked for this guide:
- Tardif JC, Kouz S, Waters DD, et al. Efficacy and Safety of Low-Dose Colchicine after Myocardial Infarction. N Engl J Med. 2019;381(26):2497-2505.
- Bouabdallaoui N, et al. Time-to-treatment initiation of colchicine and cardiovascular outcomes after myocardial infarction in COLCOT. Eur Heart J. 2020;41(42):4092-4099.
- Byrne RA, et al. 2023 ESC Guidelines for the management of acute coronary syndromes. Eur Heart J. 2023.
- Key messages and critical approach of the 2024 ESC guidelines on chronic coronary syndromes. ScienceDirect, 2025 (documents the IIa to IIb downgrade).
- Nidorf SM, et al. Colchicine in Patients with Chronic Coronary Disease (LoDoCo2). N Engl J Med. 2020;383(19):1838-1847.
- Wiki Journal Club. COLCOT summary, accessed July 2026.