Chemical formula: C₂₂H₂₅NO₆ Molecular mass: 399.443 g/mol PubChem compound: 2833
The mechanism of action of colchicine in the treatment of gout is not clearly understood. Colchicine is considered to act against the inflammatory response to urate crystals, by possibly inhibiting the migration of granulocytes into the inflamed area. Other properties of colchicine, such as interaction with the microtubules, could also contribute to the operation. Onset of action is approximately 12 hours after oral administration and is maximal after 1 to 2 days.
In the AGREE (Acute Gout Flare Receiving Colchicine Evaluation) study low- and high-dose colchicine were compared using a randomized, placebo-controlled design. The high-dose prolonged colchicine regimen (4.8 mg total over 6 hours) was compared with a placebo and a low-dose abbreviated regimen (1.8 mg total over 1 hour, i.e. 1.2 mg followed by 0.6 mg in 1 hour). Both colchicine regimens were significantly more effective than placebo, with 32.7% responders in the high-dose group, 37.8% responders in the low-dose group, and 15.5% responders in the placebo group (p=0.034 and p=0.005, respectively, versus placebo). The results at the primary 24-hour end point demonstrate superior safety of low-dose colchicine, without loss of efficacy, relative to high-dose colchicine for early acute gout flare (self-administered within 12 hours of flare onset). The pharmacokinetic analysis performed in this study showed that the colchicine plasma concentration was decreased substantially from about 12 hours after administration in healthy volunteers.
Colchicine prophylaxis (0.6 mg twice daily) during initiation of allopurinol for chronic gouty arthritis reduced the frequency and severity of acute flares, and reduced the likelihood of recurrent flares. Treatment may be continued for up to 6 months, based on clinical data. Prospective randomized controlled trials are needed to further evaluate flare prophylaxis for up to 6 months, after 6 months, and over time.
Colchicine is rapidly and almost completely absorbed after oral administration. Maximum plasma concentrations are met usually after 30 to 120 minutes. The terminal half-life is 3 to 10 hours. Plasma protein binding is approximately 30%. Colchicine is partially metabolised in the liver and then in part via the bile. It accumulates in leucocytes. Colchicine is largely excreted (80%) in unchanged form and as metabolites in the faeces. 10-20% is excreted in the urine.
Colchicine is significantly excreted in urine in healthy subjects. Clearance of colchicine is decreased in patients with impaired renal function. Total body clearance of colchicine was reduced by 75% in patients with end-stage renal disease undergoing dialysis.
The influence of renal impairment on the pharmacokinetics of colchicine was assessed in a study in patients with familial Mediterranean fever (FMF), 5 women and 4 men, with (n=4) and without (n=5) renal impairment. The mean age was 30 years (range 19-42 years). All 5 patients with renal impairment had biopsy-proven amyloidosis; 4 were on routine hemodialysis and 1 had a serum creatinine CL of 15 ml/min. They could therefore be classified as having severe renal impairment. Subjects received 1 mg colchicine except for 1 subject with cirrhosis who received 500 micrograms. A 4-fold decrease in colchicine CL was observed in subjects with renal impairment compared to those with normal renal function (0.168 ± 0.063 l/h/kg vs. 0.727 ± 0.110 l/h/kg). The terminal half-life was 18.8 ± 1.2 h for subjects with severe renal impairment and 4.4 ± 1.0 h for those with normal renal function. The volume of distribution was similar between groups. The patient with cirrhosis had a 10-fold lower CL compared to the subjects with normal renal function.
No pharmacokinetics data are available in children.
In one study, a bacterial test indicated that colchicine has a slight mutagenic effect.
However, two other bacterial tests and a test in Drosophila melanogaster found that colchicine was not mutagenic.
Tests have shown that colchicine induces chromosomal aberrations and micronuclei, and causes some DNA damage.
Tests in animals have shown that colchicine is teratogenic.
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