Absorption
In healthy adults, GLOPERBA reached a mean Cmax of 2.16 ± 0.87 ng/mL in 1 hour (range 0.5 to 2 hours) after a single dose administered under fasting conditions. A minimal food effect was observed when GLOPERBA was administered following a high fat, high calorie meal. A slight decrease in Cmax was observed; however, the overall extent of absorption based on AUC0-t and AUC0-inf, was similar in the fed and fasted states. The absolute bioavailability of colchicine is reported to be approximately 45%. Mean pharmacokinetic parameter values for GLOPERBA in healthy adults are shown in Table1.
Table 1:
Mean Pharmacokinetic Parameter Estimates for GLOPERBA in Healthy Adults
|
| Parameter | GLOPERBA, 0.6 mg (0.12 mg/mL, 5 mL) Fasted (N=34) | GLOPERBA, 0.6 mg (0.12 mg/mL, 5 mL) Fed (N=34) |
| Cmax (ng/mL) | 2.16 (0.87) | 1.68 (0.39) |
| AUC0-t (h∙ng/mL) | 18.59 (4.64) | 17.20 (4.23) |
| AUC0-inf (h∙ng/mL) | 19.90 (4.74) | 18.47 (4.29) |
| Tmax (h) (Min-Max) | 1.00 (0.50: 2.00) | 2.00 (1.00: 4.00) |
| t1/2 (h) | 31.04 (5.99) | 30.54 (5.22) |
|
Distribution
The mean apparent volume of distribution(Vz/F) of GLOPERBA in healthy adults was approximately 1420 L. Colchicine binding to serum protein is reported to be low (39%) primarily due to albumin regardless of concentration.
Colchicine crosses the placenta (plasma levels in the fetus are reported to be approximately 15% of the maternal concentration) [see Use in Specific Populations (8.1)]. Colchicine also distributes into breast milk at concentrations similar to those found in the maternal serum [see Use in Specific Populations (8.2)].
Metabolism
In vitro studies using human liver microsomes have shown that CYP3A4 is involved in the metabolism of colchicine to 2-O-demethylcolchicine (2-DMC) and 3-O-demethylcolchicine (3-DMC). Glucuronidation is also believed to be a metabolic pathway for colchicine.
Elimination
The mean elimination half-life of GLOPERBA in healthy adults is 31 hours (± 6 hours). In a published study in healthy adults approximately 40 to 65% of a single 1-mg oral dose of colchicine was reported to be recovered unchanged in urine. Enterohepatic recirculation and biliary excretion are postulated to play a role in colchicine elimination. Colchicine is also a substrate of P-gp, and P-gp efflux is postulated to play an important role in colchicine disposition.
Specific Populations
There is no difference between men and women in the pharmacokinetic disposition of colchicine.
Pediatric Patients: Pharmacokinetics of colchicine were not evaluated in pediatric patients.
Geriatric Patients: Pharmacokinetics of GLOPERBA have not been determined in elderly patients. A published report described the pharmacokinetics of a 1-mg oral colchicine tablet dose 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/minute (range 25 to 75 mL/minute). 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.
Patients with 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 hours vs. 4.4 hours) as compared to subjects with normal renal function [see Use in Specific Populations (8.6)].
Patients with 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 Use in Specific Populations (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 and P-gp inhibitors in healthy subjects have been conducted with GOLPERBA. Carvedilol 20 to 40 mg QD (considered a P-gp inhibitor), amlodipine 5 to 10 mg QD (considered a weak inhibitor of CYP3A4) and ciprofloxacin 500 mg BID (considered a moderate CYP3A4 inhibitor) did not cause any significant changes in colchicine systemic levels. Co-administration with posaconazole 300 mg QD (considered a strong CYP3A4 inhibitor) increased AUC by approximately 3-fold.
These results should not be extrapolated to other inhibitors as colchicine is known to be a substrate for CYP3A4 and P-gp, and case reports of colchicine toxicity associated with the co-administration of CYP3A4 and P-gp inhibitors (i.e., clarithromycin) have been published.
Fatal drug interactions have been reported when colchicine is administered with clarithromycin, a dual inhibitor of CYP3A4 and P-gp. Toxicities have also been reported when colchicine is administered with inhibitors of CYP3A4 that may not be potent inhibitors of P-gp (e.g., grapefruit juice), or inhibitors of P-gp that may not be potent inhibitors of CYP3A4 (e.g., cyclosporine). If treatment with a P-gp and CYP3A4 inhibitor is required in patients with normal renal and hepatic function, the patients’ dose of colchicine may need to be reduced or interrupted.