This trial seeks to assess the feasibility of a full-scale, double-blind, placebo-controlled, randomized trial assessing whether low-dose colchicine (0.5 mg daily) reduces the risk of post-thrombotic syndrome (PTS) in patients with proximal lower extremity deep vein thrombosis (DVT).

Eligible and consenting patients will be randomized via a central web-based randomization system (1:1 ratio) to receive one tablet of colchicine 0.5 mg or identical matching placebo daily starting within 7 days of initiation of anticoagulation for acute, symptomatic, proximal lower extremity Deep Vein Thrombosis (DVT) for a treatment course of 180 days (+/- 7 days). Study drug will start within 24 hours of randomization. The type, dose, and duration of anticoagulant therapy : unfractionated heparin, Low Molecular Weight Heparin (LMWH), fondaparinux, Direct Oral Anticoagulation (DOAC) or Vitamin K Agonist (VKA) will be left to the discretion of the treating physician or local investigator. The study drug will be continued until the end of the treatment period (180 days +/- 7 days). All patients will be observed until the end of study follow-up (365 days +/- 7 days).

Inclusion Criteria:

• Consenting patients 18 years of age or older with a first, acute, symptomatic proximal (popliteal vein or more proximal) objectively confirmed DVT of the lower extremity will be eligible to participate in the study.

Exclusion Criteria:

1. History of an allergic reaction or significant sensitivity to colchicine.
2. Requirement of colchicine for other indications.
3. Active or chronic diarrhea, or documented inflammatory bowel disease (i.e., Crohn's disease or ulcerative colitis), collagenous colitis or irritable bowel syndrome or existing blood dyscrasias.
4. Known or suspected, recent (<30 days) or active infections (acute or chronic).
5. History of cirrhosis, chronic active hepatitis, or severe liver disease.
6. Recent (<30 days) or chronic use of systemic (oral, intravenous) immunosuppressive drugs (including but not limited to steroids, tumor necrosis factor-alpha blockers, cyclosporine).
7. Known active cancer.
8. Any of the following as measured within the past 1-3 months or at screening: alanine, or aspartate aminotransferase >3 times the upper limit of normal, total bilirubin >2 times the upper limit of normal and a creatinine clearance by Cockcroft-Gault formula <30 mL/min.
9. Pregnancy, breast feeding or may be considering pregnancy during the study period or women of childbearing potential unwilling to use appropriate contraception during sex;
10. The use of medication with known drug-to-drug interactions (including but not limited to erythromycin or clarithromycin).
11. Unable or unwilling to provide consent.

To be developed

Upon completion of the full-scale trial

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