The COLchicine and Atrial FIBrillation Trial

Inclusion Criteria:

1. Living address in the Capital Region of Denmark
2. Age > 18
3. Diagnosed with paroxysmic/persistent AF.
4. Planned or acute admission for cardioversion of AF with successful outcome.
5. Female participants should either not be of childbearing potential, defined aspostmenopausal for at least 1 year or surgically sterile, or is of childbearingpotential and practicing one of the following methods of contraception throughout thestudy and for 30 days after study completion: Hormonal contraception (oralcontraceptives, contraceptive implant, injectable birth control, contraceptive patch,or vaginal ring) or intrauterine device
6. Participants will have given written, informed consent and are able and willing tocomply with the requirements of the study protocol.
7. Optimal background therapy (in relation to comorbidities and development of heartfailure / thromboembolic event) for AF as judged by the investigator.

Exclusion Criteria:

1. Colchicine treatment for another cause, e.g. gout
2. Allergy/hypersensitivity to colchicine
3. Uncontrolled hypertension (systolic BP >180 mmHg or diastolic BP >110 mmHg)
4. History of malignancy of any organ system excluding a successfully treatednon-metastatic cutaneous squamous cell or basal cell carcinoma, localized prostatecancer and/or localized carcinoma in situ of the cervix
5. Cirrhosis, chronic active hepatitis or other severe hepatic disease
6. Hemodialysis
7. Estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73 m2
8. Systemic treatment with moderate or strong cytochrome P450 3A4 (CYP3A4) inhibitors orP-glycoprotein inhibitors (list in Appendix 1)
9. Permanent AF
10. Female participants who are pregnant, lactating, or considering becoming pregnantduring the study or for 6 months after study completion
11. Significant drug or alcohol abuse during the last year
12. Current use of or plans to initiate chronic systemic steroid therapy during the study (topical or inhaled steroids are allowed)
13. Planned ablation procedure as treatment for AF
14. If cardiovascular surgery or ablation has been done the past three months prior toinclusion.
15. Chronic inflammatory bowel disease (Crohn's disease or ulcerative colitis) or chronicdiarrhea
16. Use of other investigational drugs within 30 days of the time of enrollment
17. Any surgical or medical condition, which in the opinion of the investigator, may placethe patient at higher risk from his/her participation in the study, or is likely toprevent the patient from complying with the requirements of the study or completingthe study.
18. Suspected AF, confirmed with ECG, at time of inclusion and randomization