[Colchicine: recent data on pharmacokinetics and clinical pharmacology]

Colchicine is widely used in the treatment of acute goutty arthritis. Recently, colchicine was shown to be effective in inflammatory diseases such as familial Mediterranean fever. Two proteins can modulate its pharmacokinetics: tubulin, the specific intracellular receptor for colchicine which determines the plasma half-life, and P-glycoprotein, an active efflux pump towards some anticancer drugs which regulates colchicine absorption, distribution, and elimination. Therapeutic dosage is monitored empirically, by the control of the balance between the occurrence of side effects and the clinical efficacy. Recently, using a specific and sensitive radioimmunoassay, the investigation of plasma concentrations during single and multiple dose studies has allowed to define the colchicine pharmacokinetic parameters. Following oral route, colchicine bioavailability is extremely variable (from 24 to 88% of the administered dose), the distribution volume is elevated (7 l/kg) but the binding to albumin is moderate. Colchicine elimination occurred mainly via hepatic pathways and the elimination half-life ranged from 20 to 40 hours. In multiple dose study (1 mg/d), the steady-state is reached 8 days after the first oral administration and plasma concentrations ranged from 0.3 to 2.5 ng/ml. Pharmacokinetic/pharmacodynamic studies show that the biological effects of colchicine were not related to plasma concentrations but with intraleukocyte concentrations. Drug interactions may occur when colchicine is associated to drugs which interact with cytochrome P450 and/or P-glycoprotein and modify renal and/or hepatic clearances. The therapeutic drug monitoring of colchicine during these circumstances could allow to prevent the observation of side effects.