Colchicine

Mechanism

💊 Common Business Names

Colchimax, Colchicina Kern, Colcrys, Mitigare, Goutnil.

🔬 Pharmacological Group

Inhibitor of tubulin polymerization. Antigout and cellular immunomodulator.

Mechanism of Action

Collchicine selectively inhibits microtubule network function in inflammatory immune cells:

• Binding to the Active Site of Tubulin: It binds reversibly covalently to soluble tubulin dimers (α and β), preventing their rapid polymerization and inhibiting cellular self-assembly of cytoplasmic microtubules.
• Blockade of Cellular Recruitment and Chemotaxis:
  1. Inhibition of Neutrophil Migration: When the cellular microtubule network is disorganized, the neutrophil loses the plasticity of its cytoskeleton necessary for endothelial adhesion, chemotaxis and capillary transmigration (diapedesis) towards the joint space rich in monosodium urate crystals (MSU).
  2. Blocking the NLRP3 Inflammasome: Interferes with the dural assembly of the NLRP3 inflammasome within the cytoplasm of the activated macrophage, potently suppressing the maturation and release of interleukin-1 beta (IL-1β), the cytokine initiating the gout attack.
  3. Inhibition of Lysosomal Degranulation: Decreases the local release of lysosomal proteases and hydrolases from phagocytes during crystal phagocytosis, mitigating dural joint inflammation.

Pharmacokinetics

Key Pharmacokinetics

Indicators and dose

Dosage and Adjustment

• Adults (Treatment of Acute Gout Attack):
  • Low Dose Precision Dosing Protocol: Administer immediately at the first signs of an acute attack 1.0 mg of colchicine orally, followed by 0.5 mg or 0.6 mg after 1 hour. Do not exceed 1.5 - 1.8 mg total in the next 24 hours.
  • (The historical protocol of administering 0.5 mg every hour until severe diarrhea is induced or pain is relieved is currently outlawed and out of use worldwide clinically due to unnecessary toxicity.)
• Adults (Attack Prophylaxis when Initiating Hypourice-lowering Therapy):
  • 0.5 mg to 1.0 mg orally once daily for a minimum of 3 to 6 months as tolerated.
• Pediatrics: Not recommended for gout; evaluable only in the management of Familial Mediterranean Fever in people over 4 years of age at doses of 0.3 - 1.2 mg/day orally adjusted to clinical response.
• Adjustment in Kidney Failure:
  • Cl_cr 30-59 mL/min: Do not absolutely exceed 0.5 - 0.6 mg/day for maintenance, and space the acute attack treatments at least a minimum of 14 days between cycles.
  • Cl_cr < 30 mL/min: Contraindicated for chronic prophylactic use. For acute attacks, it is advisable to reduce the starting dose to a maximum of 0.5 mg in a single dose and avoid repeating the drug.
• Adjustment in Liver Failure: Avoid in severe liver failure compensated by the risk of unpurified fecal accumulation.

Security

Contraindications

• Absolute: Severe renal failure (Cl_cr < 30 mL/min) in patients who simultaneously consume CYP3A4 or P-gp inhibitors; severe hepatic impairment (Child-Pugh C) with identical coadministration; history of hypersensitivity to the active ingredient; blood dyscrasias or pre-existing aplastic anemia.
• Relative: Elderly patients who are dehydrated or have moderate cardiac dysfunction.

Adverse Effects (ADR)

• Common / Dose Limiting: Diffuse abdominal cramping pain, nausea, repeated vomiting, profuse watery diarrhea (secondary to mitotic blockage of the epithelial cells of the mucosa of the intestinal tract with rapid cell turnover; serves as a warning signal of imminent systemic toxicity that requires immediate suspension of the dose).
• Rare / Serious: Severe myelotoxicity (leukopenia, extreme neutropenia with opportunistic sepsis, thrombocytopenia); Colchicine Neuromyopathy (progressive weakness of the proximal muscles, increase in serum CPK due to mitochondrial damage of the myocyte and peripheral nerve, favored in nephropathies); total irreversible alopecia; transient azoospermia. Fatal multiorgan failure in overdose.

Critical Alert: Deadly Synergism of Interactions with CYP3A4 and P-gp

As colchicine is a critical biological substrate of P-glycoprotein (P-gp) and CYP3A4, simultaneous coadministration with strong inhibitors of these proteins (such as Clarithromycin, Erythromycin, Ketoconazole, Itraconazole, Cyclosporin, Ritonavir or Verapamil) in patients with pre-existing moderate renal or hepatic failure, may induce an absolute blockage of its clearance. Plasma concentrations of colchicine rise drastically instantaneously, causing a clinical picture of fulminant multisystem cellular toxicity with a fatal course characterized by refractory multiple organ failure, hemodynamic shock, extreme aplastic pancytopenia and generalized myopathy.

Drug Interactions

• Statins (Atorvastatin, Simvastatin) or Fibrates: High synergism that notably increases the incidence of myopathy or severe rhabdomyolysis, requiring close control of serum CPK.
• Potent P-gp and CYP3A4 inhibitors: Absolutely contraindicated in kidney or liver patients; and require drastic dose reductions of 50-75% of colchicine in healthy patients.
• Acetylsalicylic acid: It slightly decreases its excretion due to competition in the active excretion of the renal tubule.

Pregnancy and Breastfeeding

Classified in FDA Category C. It quickly crosses the placenta and exerts direct cytotoxic effects by cellular mitotic blockade, being associated with a minor increase in abortions and possible malformations in animals. Prophylactic therapy should be suspended in women with a desire to become pregnant. Breastfeeding: Compatible with caution; It is excreted in moderate quantities in milk that have not been shown to induce clinical toxicity in infants if low and spaced maternal doses are respected.