Colchicine

Colchicine is a pharmaceutical alkaloid (C₂₂H₂₅NO₆, MW 399.44 g/mol), not a nutritional compound. It is a tricyclic tropane alkaloid originally derived from Colchicum autumnale (autumn crocus) and Gloriosa superba. It contains no macronutrients, vitamins, minerals, fiber, or protein of nutritional relevance. Key chemical features: • Active compound: Colchicine — a lipophilic alkaloid with three rings (trimethoxyphenyl ring A, seven-membered ring B, tropolone ring C with acetamide group). • Bioavailability: Oral bioavailability approximately 45% (range 24–88%), with rapid gastrointestinal absorption; peak plasma concentration (Cmax) reached in 0.5–2 hours. • Distribution: Large volume of distribution (~5–8 L/kg), extensive tissue binding, particularly to intracellular tubulin. Concentrates in leukocytes (especially neutrophils) at levels 16-fold higher than plasma. • Metabolism: Primarily hepatic via CYP3A4-mediated demethylation; also a substrate of P-glycoprotein (P-gp) efflux transporter. Major metabolite: 2-O-demethylcolchicine and 3-O-demethylcolchicine (both less active). • Elimination half-life: 20–40 hours in plasma; however, leukocyte half-life is substantially longer (~60 hours), contributing to prolonged pharmacodynamic effects. • Enterohepatic recirculation: Significant; 10–20% of dose excreted unchanged in urine, with biliary/fecal excretion accounting for a major elimination route. • Typical therapeutic doses: 0.5–1.2 mg/day for prophylaxis; 1.2 mg followed by 0.6 mg one hour later for acute gout flare. • Narrow therapeutic index: Toxic dose is close to therapeutic dose; doses exceeding 0.5 mg/kg can be fatal. • Natural source concentration: Colchicum autumnale corms contain approximately 0.1–0.8% colchicine by dry weight; seeds contain up to 0.4–1.2%. Gloriosa superba tubers contain 0.7–1.2%. • No caloric value, no essential nutrient content. This is strictly a pharmacologically active compound, not a food or dietary supplement.