CLINICAL PHARMACOLOGY
Miglitol is a desoxynojirimycin derivative that delays the digestion of ingested carbohydrates, thereby
resulting in a smaller rise in blood glucose concentration following meals. As a consequence of plasma
glucose reduction, GLYSET Tablets reduce levels of glycosylated hemoglobin in patients with Type II
(non-insulin-dependent) diabetes mellitus. Systemic nonenzymatic protein glycosylation, as reflected by
levels of glycosylated hemoglobin, is a function of average blood glucose concentration over time.
Mechanism Of Action
In contrast to sulfonylureas, GLYSET does not enhance insulin secretion. The antihyperglycemic action
of miglitol results from a reversible inhibition of membrane-bound intestinal α-glucoside hydrolase
enzymes. Membrane-bound intestinal α-glucosidases hydrolyze oligosaccharides and disaccharides to
glucose and other monosaccharides in the brush border of the small intestine. In diabetic patients, this
enzyme inhibition results in delayed glucose absorption and lowering of postprandial hyperglycemia.
Because its mechanism of action is different, the effect of GLYSET to enhance glycemic control is
additive to that of sulfonylureas when used in combination. In addition, GLYSET diminishes the
insulinotropic and weight-increasing effects of sulfonylureas.
Miglitol has minor inhibitory activity against lactase and consequently, at the recommended doses,
would not be expected to induce lactose intolerance.
Pharmacokinetics
Absorption
Absorption of miglitol is saturable at high doses: a dose of 25 mg is completely absorbed, whereas a
dose of 100 mg is 50% – 70% absorbed. For all doses, peak concentrations are reached in 2 to 3 hours.
There is no evidence that systemic absorption of miglitol contributes to its therapeutic effect.
Distribution
The protein binding of miglitol is negligible (<4.0%). Miglitol has a volume of distribution of 0.18
L/kg, consistent with distribution primarily into the extracellular fluid.
Metabolism
Miglitol is not metabolized in humans or in any animal species studied. No metabolites have been
detected in plasma, urine or feces, indicating a lack of either systemic or pre-systemic metabolism.
Excretion
Miglitol is eliminated by renal excretion as unchanged drug. Following a 25 mg dose, over 95% of the
dose is recovered in the urine within 24 hours. At higher doses, the cumulative recovery of drug from
urine is somewhat lower due to the incomplete bioavailability. The elimination half-life of miglitol
from plasma is approximately 2 hours.
Special Populations
Renal Impairment
Because miglitol is excreted primarily by the kidneys, accumulation of miglitol is expected in patients
with renal impairment. Patients with creatinine clearance <25 mL/min taking 25 mg 3 times daily,
exhibited a greater than two-fold increase in miglitol plasma levels as compared to subjects with
creatinine clearance >60 mL/min. Dosage adjustment to correct the increased plasma concentrations is
not feasible because miglitol acts locally. Little information is available on the safety of miglitol in
patients with creatinine clearance <25 mL/min. Therefore, treatment of these patients with miglitol is not
recommended.
Hepatic Impairment
Miglitol pharmacokinetics were not altered in cirrhotic patients relative to healthy control subjects.
Since miglitol is not metabolized, no influence of hepatic function on the kinetics of miglitol is
expected.
Gender
No significant difference in the pharmacokinetics of miglitol was observed between elderly men and
women when body weight was considered.
Race
Several pharmacokinetic studies were conducted in Japanese volunteers, with results similar to those
observed in Caucasians. A study comparing the pharmacodynamic response to a single 50 mg dose in
Black and Caucasian healthy volunteers indicated similar glucose and insulin responses in both
populations.
Clinical Studies
Clinical Experience in Non-Ins ulin-Dependent Diabetes Mellitus (NIDDM) Patients on Dietary
Treatment Only
GLYSET Tablets were evaluated in two U.S. and three non-U.S. controlled, fixed-dose, monotherapy
studies, in which 735 patients treated with GLYSET were evaluated for efficacy analyses (see Table 1).
In Study 1, a 1-year study in which GLYSET was evaluated as monotherapy and also as combination
therapy, there was a statistically significantly smaller increase in mean glycosylated hemoglobin
(HbA1c) over time in the miglitol 50 mg 3 times daily monotherapy arm compared to placebo.
Significant reductions in mean fasting and postprandial plasma glucose levels and in mean postprandial
insulin levels were observed in patients treated with GLYSET compared with the placebo group.
In Study 2, a 14-week study, there was a significant decrease in HbA1c in patients receiving GLYSET
50 mg 3 times daily or 100 mg 3 times daily compared to placebo. In addition, there were significant
reductions in postprandial plasma glucose and postprandial serum insulin levels compared to placebo.
Study 3, was a 6-month dose-ranging trial evaluating GLYSET at doses from 25 mg 3 times daily, to 200
mg 3 times daily. GLYSET produced a greater reduction in HbA1c than placebo at all doses, although
the effect was statistically significant at the 100 mg 3 times daily and 200 mg 3 times daily. In addition,
all doses of GLYSET produced significant reductions in postprandial plasma glucose and postprandial
insulin levels compared to placebo.
Studies 4 and 5 were 6-month studies evaluating GLYSET at 50 and 100 mg 3 times daily, and 100 mg 3
times daily, respectively. As compared to placebo, GLYSET produced reductions in HbA1c, as well as
a significant reduction in postprandial plasma glucose in both studies at the doses employed.
Table 1 Res ults of Monotherapy Study with GLYSET
Study |
Treatment |
HbA1c
(%) |
1-hourPos tprandial Glucose
(mg/dL) |
Mean Change from Bas eline* |
Treatment
Effect† |
Mean Change from Baseline |
Treatment
Effect† |
1 (U.S.) |
Placebo |
+0.71 |
- |
+24 |
- |
GLYSET 50 mg 3
times daily |
+0.13 |
-0.58‡ |
-39 |
-63‡ |
2 (U.S.) |
Placebo |
+0.47 |
- |
+15 |
- |
GLYSET 50 mg 3
times daily |
-0.22 |
-0.69‡ |
-52 |
-67‡ |
GLYSET 100 mg 3
times daily |
-0.28 |
-0.75‡ |
-59 |
-74‡ |
3 (non-U.S.) |
Placebo |
+0.18 |
- |
+2 |
- |
GLYSET 25 mg 3
times daily |
-0.08 |
-0.26 |
-33 |
-35‡ |
GLYSET 50 mg 3
times daily |
-0.22 |
-0.40 |
-45 |
-47‡ |
GLYSET 100 mg 3
times daily |
-0.63 |
-0.81‡ |
-62 |
-64‡ |
GLYSET 200 mg 3
times daily§ |
-0.84 |
-1.02‡ |
-85 |
-87‡ |
4 ( non-U.S.) |
Placebo |
+0.01 |
- |
+8 |
- |
GLYSET 50 mg 3 times daily |
-0.35 |
-0.36‡ |
-20 |
-28‡ |
GLYSET 100 mg 3
times daily |
-0.57 |
-0.58‡ |
-25 |
-33‡ |
5 (non-U.S.) |
Placebo |
+0.32 |
- |
+17 |
- |
GLYSET 100 mg 3 times daily |
-0.43 |
-0.75‡ |
-38 |
-55‡ |
*Mean baseline ranged from 7.54 to 8.72% in these studies.
†The result of subtracting the placebo group average.
‡p≤ 0.05
§Although results for the 200 mg 3 times daily are presented for completeness, the
maximum recommended dosage of GLYSET is 100 mg 3 times daily. |
Clinical Experience In NIDDM Patients Receiving Sulfonylureas
GLYSET was studied as adjunctive therapy to a background of maximal or near-maximal sulfonylurea
(SFU) treatment in three large, double-blind, randomized studies (two U.S. and one non-U.S.) in which
471 patients treated with GLYSET were evaluated for efficacy (see Table 2).
Study 6 included patients under treatment with maximal doses of SFU at entry. At the end of this 14-
week study, the mean treatment effects on glycosylated hemoglobin (HbA1c) were -0.82% and -0.74%
for patients receiving GLYSET 50 mg 3 times daily plus SFU, and GLYSET 100 mg 3 times daily plus
SFU, respectively.
Study 7 was a 1-year study in which GLYSET at 25, 50 or 100 mg 3 times daily was added to a maximal
dose of glyburide (10 mg twice daily). At the end of this study, the mean treatment effects on HbA1c of
GLYSET when added to maximum glyburide therapy were -0.30%, -0.62%, and -0.73% with 25, 50 and
100 mg 3 times daily dosages of GLYSET, respectively.
In Study 8, the addition of GLYSET 100 mg 3 times daily to a background of treatment with glyburide
produced an additional mean treatment effect on HbA1c of -0.66%.
Table 2 Results of Combination Therapy with GLYSET Plus Sulfonylurea
(SFU)
Study |
Treatment |
HbA1c
(%) |
1-hourPos tprandial Glucose
(mg/dL) |
Mean Change from Bas eline* |
Treatment
Effect† |
Mean Change from Baseline |
Treatment
Effect† |
6 (U.S.) |
Placebo + SFU |
+0.33 |
- |
-1 |
- |
GLYSET 50 mg 3
times daily + SFU |
-0.49 |
-0.82‡ |
-69 |
-68‡ |
GLYSET 100 mg 3
times daily + SFU |
-0.41 |
-0.74‡ |
-73 |
-72‡ |
7 (U.S.) |
Placebo + SFU |
+1.01 |
- |
48 |
- |
GLYSET 25 mg 3
times daily + SFU |
+0.71 |
-0.30 |
-2 |
-50‡ |
GLYSET 50 mg 3
times daily + SFU |
+0.39 |
-0.62‡ |
-13 |
-61‡ |
GLYSET 100 mg 3
times daily + SFU |
+0.28 |
-0.73‡ |
-33 |
-81‡ |
8 (non-U.S.) |
Placebo + SFU |
+0.16 |
- |
+10 |
- |
GLYSET 100 mg 3 times daily + SFU |
-0.50 |
-0.66‡ |
-36 |
-46‡ |
*Mean baseline ranged from 8.56 to 9.16% in these studies.
†The result of subtracting the placebo group average. ‡ p≤ 0.05 |
Dose Response
Results from controlled, fixed-dose studies of GLYSET as monotherapy or as combination treatment
with a sulfonylurea were combined to derive a pooled estimate of the difference from placebo in the
mean change from baseline in glycosylated hemoglobin (HbA1c) and postprandial plasma glucose as
shown in Figures 1 and 2:
Figure 1: HbA1c (%) Mean Change From Baseline: Treatment Effect Pooled Results from Controlled Fixed-Dose Studies in Table1 and 2
Figure 2: 1-Hour Postprandial Plasma Glucose Mean Change From Baseline: Treatment Effect Pooled Results from Controlled Fixed-Dose Studies in Table 1 and 2
Because of its mechanism of action, the primary pharmacologic effect of miglitol is manifested as a
reduction in postprandial plasma glucose, as shown previously in all of the major clinical trials.
GLYSET was statistically significantly different from placebo at all doses in each of the individual
studies with respect to effect on mean one-hour postprandial plasma glucose, and there is a dose
response from 25 to 100 mg 3 times daily for this efficacy parameter.