Absorption: In healthy adults, colchicine capsules when given orally reached a mean C max of 3 ng/mL in 1.3 h (range 0.7 to 2.5 h) after 0.6 mg single dose administration. 

Absolute bioavailability is reported to be approximately 45%.

Administration with food has no effect on the rate or extent of colchicine absorption.

Colchicine is not effectively removed by hemodialysis.

Distribution: Colchicine has a mean apparent volume of distribution in healthy young volunteers of approximately 5 to 8 L/kg. Colchicine binding to serum protein is about 39%, primarily to albumin. Colchicine crosses the placenta and distributes into breast milk [see Pregnancy (8.1) and Nursing Mothers (8.3)] . 

Metabolism: A published in vitro human liver microsome study showed that about 16% of colchicine is metabolized to 2-O-demethylcolchicine and 3-O-demethylcolchicine (2- and 3-DMC, respectively) by CYP3A4. Glucuronidation is also believed to be a metabolic pathway for colchicine. 

Excretion: In a published study in healthy volunteers, 40 to 65% of the total absorbed dose of colchicine (1 mg administered orally) was recovered unchanged in urine. Enterohepatic recirculation and biliary excretion are also believed to play a role in colchicine elimination. Colchicine is a substrate of P-gp and P-gp efflux is postulated to play an important role in colchicine disposition. Elimination half-life in humans was found to be 31 h (range 21.7 to 49.9 h). 

Special Populations: There is no difference between men and women in the pharmacokinetic disposition of colchicine. 

Pediatric Patients: Pharmacokinetics of colchicine was not evaluated in pediatric patients. 

Elderly: Pharmacokinetics of colchicine have not been determined in elderly patients. A published report described the pharmacokinetics of 1 mg oral colchicine tablet in four elderly women compared to six young healthy males. The mean age of the four elderly women was 83 years (range 75 to 93), mean weight was 47 kg (38 to 61 kg) and mean creatinine clearance was 46 mL/min (range 25 to 75 mL/min). Mean peak plasma levels and AUC of colchicine were two times higher in elderly subjects compared to young healthy males. It is possible that the higher exposure in the elderly subjects was due to decreased renal function. 

Renal impairment: Pharmacokinetics of colchicine in patients with mild and moderate renal impairment is not known. A published report described the disposition of colchicine (1 mg) in young adult men and women patients who had end-stage renal disease requiring dialysis compared to patients with normal renal function. Patients with end-stage renal disease had 75% lower colchicine clearance (0.17 vs. 0.73 L/hr/kg) and prolonged plasma elimination half-life (18.8 hrs vs. 4.4 hrs) as compared to subjects with normal renal function [see Renal Impairment (8.6)] . 

Hepatic impairment: Published reports on the pharmacokinetics of intravenous colchicine in patients with severe chronic liver disease, as well as those with alcoholic or primary biliary cirrhosis, and normal renal function suggest wide inter-patient variability. In some subjects with mild to moderate cirrhosis, the clearance of colchicine is significantly reduced and plasma half-life prolonged compared to healthy subjects. In subjects with primary biliary cirrhosis, no consistent trends were noted [see Hepatic Impairment (8.7)] . No pharmacokinetic data are available for patients with severe hepatic impairment (Child-Pugh C). 

Drug Interactions: Pharmacokinetic studies evaluating changes in systemic levels of colchicine when co-administered with CYP3A4 inhibitors in healthy volunteers have been conducted with colchicine capsules. While voriconazole 200 mg BID for 5 days (considered a strong CYP3A4 inhibitor) and cimetidine 800 mg BID for 5 days (considered a weak CYP3A4 inhibitor) did not cause any changes in colchicine systemic levels, fluconazole 200 mg QD for 4 days with a 400 mg loading dose (considered a moderate CYP3A4 inhibitor) increased colchicine AUC by 40%. As voriconazole, cimetidine, and fluconazole are known as CYP3A4 inhibitors that do not inhibit P-gp, these studies show that CYP3A4 inhibition by itself may not lead to clinically significant increases in colchicine systemic levels in humans, and P-gp inhibition in addition to CYP3A4 inhibition may be necessary for clinically meaningful interactions of colchicine. However, based on published case reports that indicate the presence of colchicine toxicity when colchicine is co-administered with strong to moderate CYP3A4 inhibitors such as clarithromycin, erythromycin, grapefruit juice, etc., as well as the 40% increase in systemic levels of colchicine observed with concomitantly administered fluconazole (a moderate CYP3A4 inhibitor that is not known to inhibit P-gp) in a drug-drug interaction study, the drug-drug interaction potential of colchicine with strong or moderate CYP3A4 inhibitors that do not inhibit P-gp cannot be ruled out completely. 

Co-administration of colchicine capsules with propafenone (a P-gp inhibitor) at 225 mg BID for 5 days, in a pharmacokinetic study in healthy volunteers, did not cause any changes in systemic levels of colchicine. This indicates that propafenone can be administered with colchicine capsules without any dose adjustment. However, these results should not be extrapolated to other P-gp inhibitors as colchicine is known to be a substrate for P‑gp and case reports of colchicine toxicity associated with the co-administration of P-gp inhibitors such as cyclosporine have been published.