CLINICAL PHARMACOLOGY
Mechanism Of Action
Repaglinide lowers blood
glucose levels by stimulating the release of insulin from the pancreas. This
action is dependent upon functioning beta (β) cells in the pancreatic islets.
Insulin release is glucose-dependent and diminishes at low glucose
concentrations.
Repaglinide closes
ATP-dependent potassium channels in the β-cell membrane by binding at
characterizable sites. This potassium channel blockade depolarizes the β-cell,
which leads to an opening of calcium channels. The resulting increased calcium
influx induces insulin secretion. The ion channel mechanism is highly tissue
selective with low affinity for heart and skeletal muscle.
Pharmacodynamics
A four-week, double-blind,
placebo-controlled dose-response trial was conducted in 138 patients with type
2 diabetes using doses ranging from 0.25 (not an approved dose) to 4 mg taken
with each of three meals. PRANDIN therapy resulted in dose-proportional glucose
lowering over the full dose range. Plasma insulin levels increased after meals
and reverted toward baseline before the next meal. Most of the fasting blood
glucose-lowering effect was demonstrated within 1-2 weeks.
In a double-blind,
placebo-controlled, 3-month dose titration study, PRANDIN or placebo doses for
each patient were increased weekly from 0.25 mg (not an approved dose) through
0.5, 1, and 2 mg, to a maximum of 4 mg, until a fasting plasma glucose (FPG)
level <160 mg/dL was achieved or the maximum dose reached. The dose that
achieved the targeted control or the maximum dose was continued to end of
study. FPG and 2-hour post-prandial glucose (PPG) increased in patients
receiving placebo and decreased in patients treated with repaglinide.
Differences between the repaglinide-and placebo-treated groups were -61 mg/dL
(FPG) and -104 mg/dL (PPG) (Table 4).
Table 4: PRANDIN vs Placebo : Mean Change from Baseline after 3 Months of
Treatment
|
Repaglinide |
Placebo |
N |
66 |
33 |
Fasting Plasma Glucose (mg/dL) |
Baseline |
220.2 |
215.3 |
Change from baseline (at last visit) |
-31.0* |
30.3 |
Post Prandial Glucose (mg/dL) |
Baseline |
261.7 |
245.2 |
Change from baseline (at last visit) |
-47.6* |
56.5 |
*: p< 0.05 for between group
difference |
The dosing of PRANDIN relative
to meal-related insulin release was studied in three trials including 58
patients. Glycemic control was maintained during a period in which the meal and
dosing pattern was varied (2, 3 or 4 meals per day; before meals x 2, 3, or 4)
compared with a period of 3 regular meals and 3 doses per day (before meals x
3). Blood glucose-lowering effect did not differ when PRANDIN was administered
at the start of a meal, 15 minutes before, or 30 minutes before the meal.
Pharmacokinetics
The pharmacokinetic parameters
of repaglinide obtained from a single-dose, crossover study in healthy subjects
and from a multiple-dose, parallel, dose-proportionality (0.5, 1, 2 and
4 mg) study in patients with type 2 diabetes are summarized in Tables 5 and 6.
These data indicate that repaglinide did not accumulate in serum. Clearance of
oral repaglinide did not change over the 0.5 -4 mg dose range, indicating a
linear relationship between dose and plasma drug levels.
Table 5: Pharmacokinetic Parameters for Repaglinide in
Healthy Subjects
Parameter |
|
CL (based on i.v.) |
38 ± 16 L/hr |
Vss (based on i.v.) |
31 ± 12 L |
AbsBio |
56 ± 9% |
CL = total body clearance Vss =
volume of distribution at steady state AbsBio = absolute bioavailability |
Table 6: Pharmacokinetic Parameters for Repaglinide in
Patients with Type 2 Diabetes*
Dose(m) |
Pharmacokinetic Parameter |
AUC0-24 hr (ng/mL*hr) Mean (SD) |
Cmax0-5 hr (ng/mL) Mean (SD) |
0.5 |
68.9 (154.4) |
9.8 (10.2) |
1 |
125.8 (129.8) |
18.3 (9.1) |
2 |
152.4 (89.60) |
26.0 (13.0) |
4 |
447.4 (211.3) |
65.8 (30.1) |
|
T max0-5 h rMeans (SD) |
T½ Means (Ind Range) |
0.5 -4 |
1.0 - 1.4 (0.3 - 0.5) hr |
1.0 - 1.4 (0.4 - 8.0) hr |
*dosed preprandially with three meals |
Absorption
After oral administration,
repaglinide is completely absorbed from the gastrointestinal tract. After
single and multiple oral doses in healthy subjects or in patients, peak plasma
drug levels (Cmax) occur within 1 hour (Tmax). Repaglinide is eliminated from
the blood stream with a half-life of approximately 1 hour. The mean absolute
bioavailability is 56%. When repaglinide was given with food, the meanTmax wasnotchanged,butthe
meanCmax and AUC(areaunderthetime/plasmaconcentrationcurve) weredecreased20%and
12.4%, respectively.
Distribution
After intravenous (IV) dosing in healthy subjects, the
volume of distribution at steady state (Vss) was 31 L, and the total body
clearance (CL) was 38 L/h. Protein binding and
binding to human serum albumin was greater than 98%.
Metabolism And Elimination
Repaglinide is completely metabolized by oxidative
biotransformation and direct conjugation with glucuronic acid after either an
IV or oral dose. The major metabolites are an oxidized dicarboxylic acid (M2),
the aromatic amine (M1), and the acyl glucuronide (M7). The cytochrome P-450
enzyme system, specifically 2C8 and 3A4, have been shown to be involved in the
N-dealkylation of repaglinide to M2 and the further oxidation to M1.
Metabolites do not contribute to the glucose-lowering effect of repaglinide.
Within 96 hours after dosing with 14C-repaglinide as a single, oral
dose, approximately 90% of the radiolabel was recovered in the feces and
approximately 8% in the urine. Only 0.1% of the dose is cleared in the urine as
parent compound. The major metabolite (M2) accounted for 60% of the administered
dose. Less than 2% of parent drug was recovered in feces. Repaglinide appears
to be a substrate for active hepatic uptake transporter (organic anion
transporting protein OATP1B1).
Variability Of Exposure
Repaglinide AUC after multiple
doses of 0.25 to 4 mg with each meal varies over a wide range. The
intra-individual and inter-individual coefficients of variation were 36% and
69%, respectively. AUC over the therapeutic dose range included 69 to 1005
ng/mL*hr, but AUC exposure up to 5417 ng/mL*hr was reached in dose escalation
studies without apparent adverse consequences.
Specific Populations
Geriatric
Healthy volunteers were treated with a regimen of 2 mg
PRANDIN taken before each of 3 meals. There were no significant differences in
repaglinide pharmacokinetics between the group of patients <65 years of age
and a comparably sized group of patients ≥65 years of age [see Use In Specific
Populations].
Gender
A comparison of pharmacokinetics in males and females
showed the AUC over the 0.5 mg to 4 mg dose range to be 15% to 70% higher in
females with type 2 diabetes. This difference was not reflected in the
frequency of hypoglycemic episodes (male: 16%; female: 17%) or other adverse
events.
Race
No pharmacokinetic studies to assess the effects of race
have been performed, but in a U.S. 1-year study in patients with type 2
diabetes, the blood glucose-lowering effect was comparable between Caucasians
(n=297) and African-Americans (n=33). In a U.S. dose-response study, there was
no apparent difference in exposure (AUC) between Caucasians (n=74) and
Hispanics (n=33).
Renal Impairment
Single-dose and steady-state pharmacokinetics of
repaglinide were compared between patients with type 2 diabetes and normal
renal function (CrCl > 80 mL/min), mild to moderate renal function
impairment (CrCl = 40 – 80 mL/min), and severe renal function impairment (CrCl
= 20 – 40 mL/min). Both AUC and Cmax of repaglinide were similar in patients
with normal and mild to moderately impaired renal function (mean values 56.7
ng/mL*hr vs 57.2 ng/mL*hr and 37.5 ng/mL vs 37.7 ng/mL, respectively.) Patients
with severely reduced renal function had elevated mean AUC and Cmax values (98.0ng/mL*hr and 50.7ng/mL, respectively), but this study
showed only a weak correlation between repaglinide levels and creatinine
clearance.
Hepatic Impairment
A single-dose, open-label study was conducted in 12
healthy subjects and 12 patients with chronic liver disease (CLD) classified by
Child-Pugh scale and caffeine clearance. Patients with moderate to severe
impairment of liver function had higher and more prolonged serum concentrations
of both total and unbound repaglinide than healthy subjects (AUChealthy: 91.6
ng/mL*hr; AUCCLD patients: 368.9 ng/mL*hr; Cmax, healthy: 46.7 ng/mL; Cmax, CLD
patients: 105.4 ng/mL). AUC was statistically correlated with caffeine
clearance. No difference in glucose profiles was observed across patient
groups.
Drug-Drug Interactions
Drug interaction studies performed in healthy volunteers
show that PRANDIN had no clinically relevant effect on the pharmacokinetic
properties of digoxin, theophylline, or warfarin. Co-administration of
cimetidine with PRANDIN did not significantly alter the absorption and
disposition of repaglinide.
Additionally, the following drugs were studied in healthy
volunteers with co-administration of PRANDIN.
Table 7: Effect of Other Drugs on AUC and Cmax of
Repaglinide
Study Drug |
Dosing |
Repaglinide Dosing1 |
Repaglinide |
AUC |
Cmax |
Clarithromycin* |
250 mg BID for 4 days |
|
40% ↑ |
67% ↑ |
Clopidogrel* |
300 mg (Day 1) 75 mg QD (Day 2-3) |
0.25 mg
(Day 1 and 3) |
(day 1) 5.1 fold ↑ (3.9-6.6)
(day 3) 3.9 fold ↑ (2.9-5.3) |
2.5 fold ↑(1.8-3.5)
2.0 fold ↑ (1.3-3.1) |
Cyclosporine |
100 mg (2 doses 12 hours apart) |
|
2.5 fold↑ |
1.8 fold↑ |
Deferasirox* |
30 mg/kg QD for 4 days |
0.5 mg |
2.3 fold ↑ |
62% ↑ |
Fenofibrate |
200 mg QD for 5 days |
|
0% |
0% |
Gemfibrozil* |
600 mg BID for 3 days |
|
8.1 fold ↑ |
2.4 fold ↑ |
Itraconazole* |
100 mg BID for 3 days |
|
1.4 fold ↑ |
1.5 fold↑ |
Gemfibrozil + Itraconazole* Co-administration |
Gem: 600 mg BID for 3 days Itra: 100 mg BID for 3 days |
|
19 fold ↑ |
2.8 fold ↑ |
Ketoconazole |
200 mg QD for 4 days |
2 mg |
15% ↑ |
16%↑ |
Levonorgestrel/ethinyl Estradiol |
(0.15 mg/0.03 mg) Combination tablet QD for 21 days |
2 mg |
0% |
20% ↑ |
Nifedipine* |
10 mg TID for 4 days |
2 mg |
0% |
0% |
Rifampin* |
600 mg QD for 6-7 days |
4 mg |
32-80% ↓ |
17-79% ↓ |
Simvastatin |
20 mg QD for 4 days |
2 mg |
0% |
26% ↑ |
Trimethoprim* |
160 mg BID for 2 days |
|
61% ↑ |
41% ↑ |
160 mg QD for 1 day |
1Unless indicated all drug interactions were
observed with single dose of 0.25 mg repaglinide
↑indicates increase
↓indicates decrease
* Indicates data are from published literature |
Clinical Studies
Monotherapy Trials
A double-blind,
placebo-controlled trial was carried out in 362 patients treated for 24 weeks.
HbA1c for the PRANDIN-treated groups (1 and 4 mg groups combined) at the end of
the study was decreased compared to the placebo-treated group in treatment
naïve patients and in patients previously treated with oral hypoglycemic agents
by 2.1% and 1.7%, respectively. In this fixed-dose trial, patients who were
treatment naïve to oral hypoglycemic agent therapy and patients with a HbA1c below
8% at baseline showed greater blood glucose-lowering.
Combination Trials
PRANDIN In Combination With Metformin
PRANDIN was studied in
combination with metformin in 83 patients not satisfactorily controlled on
exercise, diet, and metformin alone. PRANDIN dosage was titrated for 4 to 8
weeks, followed by a 3-month maintenance period. Combination therapy with
PRANDIN and metformin resulted in statistically significant improvement in
HbA1c and fasting plasma glucose (FPG) compared to PRANDIN or metformin
monotherapy (Table 8). In this study where metformin dosage was kept constant,
the combination therapy of PRANDIN and metformin showed dose-sparing effects
with respect to PRANDIN. The improvement in HbA1c and FPG of the combination
group was achieved at a lower daily PRANDIN dosage than in the PRANDIN
monotherapy group (Table 8).
Table 8: PRANDIN in Combination with Metformin: Mean
Change from Baseline after 4 to 5 Months of Treatment1
|
PRANDIN Monotherapy |
PRANDIN Combination Therapy with Metformin |
Metformin Monotherapy |
N |
28 |
27 |
27 |
Median Final Dose (mg/day) |
12 |
6 (PRANDIN) 1500 (metformin) |
1500 |
HbA1C (%) |
Baseline |
8.6 |
8.3 |
8.6 |
Change from baseline |
-0.38 |
-1.41* |
-0.33 |
Fasting Plasma Glucose (mg/dL) |
Baseline |
174 |
184 |
194 |
Change from baseline |
8.8 |
-39.2* |
-4.5 |
Weight (kg) |
Baseline |
87 |
93 |
91 |
Change from baseline |
3.0 |
2.4# |
-0.90 |
1: based on intent-to-treat analysis
*: p< 0.05, for pairwise comparisons with PRANDIN and
metformin monotherapy.
#: p< 0.05, for pairwise comparison with metformin. |
PRANDIN In Combination With
Pioglitazone
A combination therapy regimen
of PRANDIN and pioglitazone (N=123) was compared to PRANDIN alone (N=61) and
pioglitazone alone (N=62) in a 24-week trial that enrolled 246 patients
previously treated with sulfonylurea or metformin monotherapy (HbA1c >
7.0%). PRANDIN dosage was titrated during the first 12 weeks, followed by a
12-week maintenance period. Combination therapy resulted in statistically
significant improvement in HbA1c and FPG compared to monotherapy (Figure 1).
The changes from baseline for completers in FPG (mg/dL) and HbA1c (%),
respectively were: -39.8 mg/dL and -0.1% for PRANDIN, -35.3 mg/dL and -0.1% for
pioglitazone and -92.4 mg/dL and -1.9% for the combination. In this study where
pioglitazone dosage was kept constant, the combination therapy group showed
dose-sparing effects with respect to PRANDIN (see Figure 1 Legend). The
improvement in HbA1c and FPG of the combination group was achieved at a lower
daily PRANDIN dosage than in the PRANDIN monotherapy group.
Figure 1: PRANDIN in Combination with Pioglitazone:
HbA1c Values
LEGEND: HbA1c values by
study week for patients who completed study (combination, N = 101; PRANDIN, N =
35, pioglitazone, N = 26). Subjects with FPG above 270 mg/dL were withdrawn
from the study. Pioglitazone dose: fixed at 30 mg/day; PRANDIN median final
dose: 6 mg/day for combination and 10 mg/day for monotherapy.
PRANDIN In Combination With Rosiglitazone
A combination therapy regimen
of PRANDIN and rosiglitazone was compared to monotherapy with either agent
alone in a 24-week trial that enrolled 252 patients previously treated with
sulfonylurea or metformin (HbA1c > 7.0%). Combination therapy resulted in
statistically significant improvement in HbA1c and FPG compared to monotherapy
(Table 9 below). The glycemic effects of the combination therapy were
dose-sparing with respect to both total daily PRANDIN dosage and total daily
rosiglitazone dosage (see Table 9 Legend). The improvement in HbA1c and FPG of
the combination therapy group was achieved with lower daily dose of PRANDIN and
rosiglitazone, as compared to the respective monotherapy groups.
Table 9: PRANDIN in Combination with Rosiglitazone:
Mean Change from Baseline in a 24-Week Study1
|
PRANDIN Monotherapy |
PRANDIN Combination Therapy with Rosiglitazone |
Rosiglitazone Monotherapy |
N |
63 |
127 |
62 |
Median Final Dose (mg/day) |
12 |
6 (PRANDIN) 4 (Rosiglitazone) |
8 |
HbA1C (%) |
Baseline |
9.3 |
9.1 |
9.0 |
Change from baseline |
-0.17 |
-1.43 * |
-0.56 |
Fasting Plasma Glucose (mg/dL) |
Baseline |
269 |
257 |
252 |
Change from baseline |
-54 |
-94* |
-67 |
Change in Weight (kg) |
+ 1.3 |
+4.5# |
+3.3 |
1: based on intent-to-treat analysis
*: p< 0.001
for comparison to either monotherapy
#: p< 0.05 for comparison to PRAND |