CLINICAL PHARMACOLOGY
Mechanism Of Action
The mechanism by which COLCRYS exerts its beneficial
effect in patients with FMF has not been fully elucidated; however, evidence
suggests that colchicine may interfere with the intracellular assembly of the
inflammasome complex present in neutrophils and monocytes that mediates
activation of interleukin-1β. Additionally, colchicine disrupts cytoskeletal
functions through inhibition of β-tubulin polymerization into
microtubules and consequently prevents the activation, degranulation and
migration of neutrophils thought to mediate some gout symptoms.
Pharmacokinetics
Absorption
In healthy adults, COLCRYS is absorbed when given orally,
reaching a mean Cmax of 2.5 ng/mL (range 1.1 to 4.4 ng/mL) in one to two hours
(range 0.5 to three hours) after a single dose administered under fasting
conditions.
Following oral administration of COLCRYS given as 1.8 mg
colchicine over one hour to healthy, young adults under fasting conditions,
colchicine appears to be readily absorbed, reaching mean maximum plasma concentrations
of 6.2 ng/mL at a median 1.81 hours (range: 1.0 to 2.5 hours). Following
administration of the nonrecommended high-dose regimen (4.8 mg over six hours),
mean maximal plasma concentrations were 6.8 ng/mL, at a median 4.47 hours
(range: 3.1 to 7.5 hours).
After 10 days on a regimen of 0.6 mg twice daily, peak
concentrations are 3.1 to 3.6 ng/mL (range 1.6 to 6.0 ng/mL), occurring 1.3 to
1.4 hours post dose (range 0.5 to 3.0 hours). Mean pharmacokinetic parameter
values in healthy adults are shown in Table 5.
Table 5: Mean (%CV) Pharmacokinetic Parameters in
Healthy Adults Given COLCRYS
Cmax (Colchicine ng/mL) |
Tmax* (h) |
Vd/F (L) |
CL/F (L/hr) |
t½ (h) |
COLCRYS 0.6 mg Single Dose (N=13) |
2.5 (28.7) |
1.5 (1.0 - 3.0) |
341.5 (54.4) |
54.1 (31.0) |
-- |
COLCRYS 0.6 mg Twice Daily x 10 Days (N=13) |
3.6 (23.7) |
1.3 (0.5 - 3.0) |
1150 (18.7) |
30.3 (19.0) |
26.6 (16.3) |
*Tmax mean (range)
CL = Dose/AUC0-t (calculated from mean values)
Vd = CL/Ke (calculated from mean values) |
In some subjects, secondary colchicine peaks are seen,
occurring between three and 36 hours post dose and ranging from 39% to 155% of
the height of the initial peak. These observations are attributed to intestinal
secretion and reabsorption and/or biliary recirculation.
Absolute bioavailability is reported to be approximately
45%.
Administration of COLCRYS with food has no effect on the
rate of colchicine absorption but does decrease the extent of colchicine by
approximately 15%. This is without clinical significance.
Distribution
The mean apparent volume of distribution in healthy young
volunteers is approximately 5 to 8 L/kg.
Colchicine binding to serum protein is low, 39 ± 5%,
primarily to albumin regardless of concentration.
Colchicine crosses the placenta (plasma levels in the
fetus are reported to be approximately 15% of the maternal concentration).
Colchicine also distributes into breast milk at concentrations similar to those
found in the maternal serum [see Pregnancy and Nursing Mothers].
Metabolism
Colchicine is demethylated to two primary metabolites,
2-O-demethylcolchicine and 3-O-demethylcolchicine (2- and 3-DMC, respectively)
and one minor metabolite, 10-O-demethylcolchicine (also known as colchiceine). In
vitro studies using human liver microsomes have shown that CYP3A4 is involved
in the metabolism of colchicine to 2-and 3-DMC. Plasma levels of these
metabolites are minimal (less than 5% of parent drug).
Elimination/Excretion
In healthy volunteers (n=12), 40% to 65% of 1 mg orally
administered colchicine was recovered unchanged in urine. Enterohepatic
recirculation and biliary excretion are also postulated to play a role in
colchicine elimination. Following multiple oral doses (0.6 mg twice daily), the
mean elimination half-lives in young healthy volunteers (mean age 25 to 28
years of age) is 26.6 to 31.2 hours. Colchicine is a substrate of P-gp.
Extracorporeal Elimination
Colchicine is not removed by hemodialysis.
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: A published report described the
pharmacokinetics of 1 mg oral colchicines 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.
A pharmacokinetic study using a single oral dose of one
0.6 mg colchicine tablet was conducted in young healthy subjects (n=20) between
the ages of 18 and 30 years and elderly subjects (n=18) between the ages of 60
and 70 years. Elderly subjects in this study had a median age of 62 years and a
mean (±SD) age of 62.83 ± 2.83 years. A statistically significant difference in
creatinine clearance (mean ± SD) was found between the two age groups (132.56 ±
23.16 mL/min for young vs. 87.02 ± 17.92 mL/min for elderly subjects,
respectively). The following pharmacokinetic parameter values (mean ± SD) were
observed for colchicine in the young and elderly subjects, respectively:
AUC0-inf (ng/hr/mL) 22.39 ± 6.95 and 25.01 ± 6.92; Cmax (ng/mL) 2.61 ± 0.71 and
2.56 ± 0.97; Tmax (hr) 1.38 ± 0.42 and 1.25 ± 0.43; apparent elimination half-life
(hr) 24.92 ± 5.34 and 30.06 ± 10.78; and clearance (mL/min) 0.0321 ± 0.0091 and
0.0292 ± 0.0071.
Clinical studies with colchicine for prophylaxis and
treatment of gout flares and for treatment of FMF did not include sufficient
numbers of patients aged 65 years and older to determine whether they respond
differently than younger patients. In general, dose selection for an elderly
patient with gout should be cautious, reflecting the greater frequency of
decreased renal function, concomitant disease or other drug therapy [see Dose
Modification for Coadministration of Interacting Drugs and Geriatric Use].
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 with FMF who had normal renal function or end-stage renal disease
requiring dialysis. 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 FMF and
normal renal function [see Dose Modification in Renal Impairment and Renal
Impairment].
Hepatic Impairment: Published reports on the
pharmacokinetics of IV colchicine in patients with severe chronic liver
disease, as well as those with alcoholic or primary biliary cirrhosis and
normal renal function suggest wide interpatient 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 Dose Modification in
Hepatic Impairment and Hepatic Impairment]. No pharmacokinetic data
are available for patients with severe hepatic impairment (Child-Pugh C).
Drug Interactions
In Vitro Drug Interactions: In vitro studies in
human liver microsomes have shown that colchicine is not an inhibitor or
inducer of CYP1A2, CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP2E1 or
CYP3A4 activity.
In Vivo Drug Interactions: The effects of
coadministration of other drugs with COLCRYS on Cmax, AUC and Cmin are
summarized in Table 6 (effect of other drugs on colchicine) and Table 7 (effect
of colchicine on other drugs). For information regarding clinical
recommendations, see Table 1 in Dose Modification for Coadministration of Interacting
Drugs [see Dose Modification for Coadministration of Interacting Drugs].
Table 6: Drug Interactions: Pharmacokinetic Parameters
for COLCRYS (Colchicine, USP) Tablets in the Presence of the Coadministered
Drug
Coadministered Drug |
Dose of Coadministered Drug (mg) |
Dose of COLCRYS (mg) |
N |
% Change in Colchicine Concentrations from Baseline (Range: Min - Max) |
Cmax |
AUC0-t |
Cyclosporine |
100 mg single dose |
0.6 mg single dose |
23 |
270.0
(62.0 to 606.9) |
259.0
(75.8 to 511.9) |
Clarithromycin |
250 mg twice daily, 7 days |
0.6 mg single dose |
23 |
227.2
(65.7 to 591.1) |
281.5
(88.7 to 851.6) |
Ketoconazole |
200 mg twice daily, 5 days |
0.6 mg single dose |
24 |
101.7
(19.6 to 219.0) |
212.2
(76.7 to 419.6) |
Ritonavir |
100 mg twice daily, 5 days |
0.6 mg single dose |
18 |
184.4
(79.2 to 447.4) |
296.0
(53.8 to 924.4) |
Verapamil |
240 mg daily, 5 days |
0.6 mg single dose |
24 |
40.1
(-47.1 to 149.5) |
103.3
(-9.8 to 217.2) |
Diltiazem |
240 mg daily, 7 days |
0.6 mg single dose |
20 |
44.2
(-46.0 to 318.3) |
93.4
(-30.2 to 338.6) |
Azithromycin |
500 mg x 1 day, then 250 mg x 4 days |
0.6 mg single dose |
21 |
21.6
(-41.7 to 222.0) |
57.1
(-24.3 to 241.1) |
Grapefruit juice |
240 mL twice daily, 4 days |
0.6 mg single dose |
21 |
-2.55
(-53.4 to 55.0) |
-2.36
(-46.4 to 62.2) |
Estrogen-containing oral contraceptives: In healthy
female volunteers given ethinyl estradiol and norethindrone (Ortho-Novum 1/35)
coadministered with COLCRYS (0.6 mg twice daily à 14 days), hormone
concentrations are not affected.
In healthy volunteers given theophylline coadministered
with COLCRYS (0.6 mg twice daily à 14 days), theophylline concentrations were
not affected.
Table 7: Drug Interactions: Pharmacokinetic Parameters
for Coadministration of Drug in the Presence of COLCRYS (Colchicine, USP)
Tablets
Coadministered Drug |
Dose of Coadministered Drug (mg) |
Dose of COLCRYS (mg) |
N |
% Change in Coadministered Drug Concentrations from Baseline (Range: Min - Max) |
Cmax |
AUC0-t |
Theophylline |
300 mg (elixir) single dose |
0.6 mg twice daily x 14 days |
27 |
1.6
(-30.4 to 23.1) |
1.6
(-28.5 to 27.1) |
Ethinyl Estradiol (Ortho-Novum 1/35) |
21-day cycle (active treatment) + 7-day placebo |
0.6 mg twice daily x 14 days |
27* |
-6.7
(-40.3 to 44.7) |
-3.0†
(-25.3 to 24.9) |
Norethindrone (Ortho-Novum 1/35) |
0.94
(-37.3 to 59.4) |
-1.6†
(-32.0 to 33.7) |
*Conducted in healthy adult females
†AUCτ |
Clinical Studies
The evidence for the efficacy of colchicine in patients
with chronic gout is derived from the published literature. Two randomized
clinical trials assessed the efficacy of colchicine 0.6 mg twice a day for the
prophylaxis of gout flares in patients with gout initiating treatment with
urate-lowering therapy. In both trials, treatment with colchicines decreased
the frequency of gout flares.
The efficacy of a low-dosage regimen of oral colchicine
(COLCRYS total dose 1.8 mg over one hour) for treatment of gout flares was
assessed in a multicenter, randomized, double-blind, placebo-controlled,
parallel group, one-week, dose-comparison study. Patients meeting American
College of Rheumatology criteria for gout were randomly assigned to three
groups: high-dose colchicine (1.2 mg, then 0.6 mg hourly à 6 hours [4.8 mg
total]); low-dose colchicine (1.2 mg, then 0.6 mg in 1 hour [1.8 mg total] followed
by five placebo doses hourly); or placebo (two capsules, then one capsule hourly
à 6 hours). Patients took the first dose within 12 hours of the onset of the flare
and recorded pain intensity (11-point Likert scale) and adverse events over 72
hours.
The efficacy of colchicine was measured based on response
to treatment in the target joint, using patient self-assessment of pain at 24
hours following the time of first dose as recorded in the diary. A responder
was one who achieved at least a 50% reduction in pain score at the 24 hour post
dose assessment relative to the pretreatment score and did not use rescue
medication prior to the actual time of 24 hour post dose assessment.
Rates of response were similar for the recommended
low-dose treatment group (38%) and the nonrecommended high-dose group (33%) but
were higher as compared to the placebo group (16%) as shown in Table 8.
Table 8: Number (%) of Responders Based on Target
Joint Pain Score at 24 Hours Post First Dose
COLCRYS Dose
Responders n (%) |
Placebo
n (%) (n=58) |
% Differences in Proportion |
Low-Dose
(n=74) |
High-Dose
(n=52) |
Low-Dose vs Placebo
(95% CI) |
High-Dose vs Placebo
(95% CI) |
28 (38%) |
17 (33%) |
9 (16%) |
22 (8, 37) |
17 (1, 33) |
Figure 1 shows the percentage of patients achieving
varying degrees of improvement in pain from baseline at 24 hours.
Figure 1 : Pain Relief on Low and High Doses of
COLCRYS and Placebo (Cumulative)
The evidence for the efficacy of colchicine in patients
with FMF is derived from the published literature. Three randomized,
placebo-controlled studies were identified. The three placebo-controlled
studies randomized a total of 48 adult patients diagnosed with FMF and reported
similar efficacy endpoints as well as inclusion and exclusion criteria.
One of the studies randomized 15 patients with FMF to a
six-month crossover study during which five patients discontinued due to study
noncompliance. The 10 patients completing the study experienced five attacks
over the course of 90 days while treated with colchicine compared to 59 attacks
over the course of 90 days while treated with placebo. Similarly, the second
study randomized 22 patients with FMF to a four-month crossover study during
which nine patients discontinued due to lack of efficacy while receiving
placebo or study noncompliance. The 13 patients completing the study experienced
18 attacks over the course of 60 days while treated with colchicines compared
to 68 attacks over the course of 60 days while treated with placebo. The third study
was discontinued after an interim analysis of six of the 11 patients enrolled
had completed the study; results could not be confirmed.
Open-label experience with colchicine in adults and
children with FMF is consistent with the randomized, controlled trial
experience and was utilized to support information on the safety profile of
colchicine and for dosing recommendations.