Colchicine Poisoning

Sources

• Rosen's Emergency Medicine, Ch. 153 (Antimitotic Toxins)
• Goodman & Gilman's Pharmacological Basis of Therapeutics, Ch. on Gout Pharmacology

Mechanism of Toxicity

• Microtubule disruption: Colchicine binds tubulin and inhibits microtubule polymerization, arresting cell division in G1 phase (antimitotic). This effect is greatest on cells with rapid turnover — GI epithelium, neutrophils, and bone marrow cells are most vulnerable.
• Impaired intracellular transport: Disruption of microtubule-based cytoskeletal function impairs secretion, motility, and structural integrity of cells throughout the body.
• Multi-system cellular failure: Beyond mitosis, colchicine depresses the respiratory center, constricts blood vessels, alters neuromuscular function, and causes GI neurogenic stimulation followed by direct depression.
• The drug has a large volume of distribution (forms tubulin complexes in tissues), long plasma half-life (~31 hours), and undergoes enterohepatic circulation — all features that prolong toxicity and limit decontamination.

Toxic Doses

Clinical Phases

Phase 1 — Gastrointestinal (0–24 hours)

• Severe nausea, vomiting, watery/bloody diarrhea
• Abdominal cramping and pain
• Hypovolemia from GI losses
• Electrolyte disturbances
• ⚠️ Often misdiagnosed as acute gastroenteritis or food poisoning

Phase 2 — Multi-Organ Failure (24–72 hours)

• Cardiovascular: Cardiogenic shock, dysrhythmias
• Pulmonary: Acute respiratory distress syndrome (ARDS)
• Hematologic: Pancytopenia (bone marrow suppression → neutropenia, thrombocytopenia, anemia)
• Hepatic: Elevated transaminases, liver failure
• Musculoskeletal: Rhabdomyolysis
• Infectious: Sepsis (from neutropenia and mucosal barrier breakdown)
• Neurologic: Ascending neuromuscular paralysis (rare at very high doses)

Phase 3 — Recovery (if survived)

• Rebound leukocytosis (white cell recovery from marrow)
• Resolution of multi-organ dysfunction
• Alopecia may occur weeks later (from damage to hair follicle mitotic cells)

Differential Diagnosis

Diagnostic Workup

• CBC: Assess for pancytopenia (early sign of bone marrow suppression)
• Serum electrolytes: Hyponatremia, hypokalemia from GI losses
• Renal function (BMP/creatinine): Assess for renal failure
• Liver function tests: Transaminases, bilirubin
• Creatine phosphokinase (CPK): Rhabdomyolysis
• ECG: Assess for dysrhythmias (QTc, QRS widening)
• Serum colchicine levels: Available via reference labs, but results are delayed and should not alter or delay emergency management

Management

There is no commercially available antidote for colchicine poisoning in the United States. Management is entirely supportive.

Decontamination

• Activated charcoal (1 g/kg PO): Administer if patient presents within 1 hour of a potentially lethal ingestion and has an intact airway. Particularly important given enterohepatic recirculation.
• Gastric lavage: May be considered in massive, very recent ingestion (< 1 hour)
• Multiple-dose activated charcoal: May interrupt enterohepatic recirculation (consider in large ingestions)

Supportive Care (cornerstone)

• Aggressive IV fluid resuscitation for hypovolemia and electrolyte replacement
• Vasopressors (norepinephrine) for refractory shock/cardiogenic failure
• Mechanical ventilation for ARDS
• Broad-spectrum antibiotics for sepsis (given expected neutropenia)
• Transfusions (PRBCs, platelets) for severe pancytopenia
• G-CSF (filgrastim): May stimulate marrow recovery in neutropenia — used empirically in severe cases
• Continuous cardiac monitoring

Therapies NOT Available / Not Useful

• No specific antidote exists in the US (colchicine-specific Fab fragments have been investigated but are not commercially available)
• Hemodialysis is not effective due to large volume of distribution and high tissue binding

Disposition

Key Drug Interactions (Increasing Toxicity Risk)

• CYP3A4 inhibitors (e.g., clarithromycin, fluconazole, cyclosporine): Increase colchicine plasma levels — potentially fatal at therapeutic doses
• P-glycoprotein inhibitors: Same effect; colchicine is a P-gp substrate

Important Clinical Pearl