Abstract
The comparative effects of glimepiride (Amaryl; HOE 490) and glibenclamide on insulin
and glucose metabolism under hyperglycaemic and hyperinsulinaemic, euglycaemic clamp
conditions were studied in a double-blind, placebo-controlled, crossover trial. Patients
with sulfonylurea-controlled non-insulin-dependent diabetes were allocated in random
order to placebo, glimepiride (5 mg) or glibenclamide (5 mg) and received one week
treatment of each with no wash-out period. At the end of each treatment week a clamp
study was performed. Two protocols were used. Protocol I used a 5 h hyperglycaemic
clamp at 10.9 mmol/l whole blood glucose concentration and Protocol II used a 3 h
hyperinsulinaemic, euglycaemic clamp at 3.5 mmol/l whole blood glucose concentration.
Both glimepiride and glibenclamide exhibited a hypoglycaemic effect. A significant
redution in fasting whole blood glucose concentration was observed after one-week
treatment of each active agent (fasting glucose: glimepiride v. placebo, 9.3 ± 0.7
v. 10.7 ± 0.8 mmol/l, p < 0.02; glibenclamide v. placebo, 8.9 ± 0.9 v. 10.7 ± 0.8
mmol/l, p < 0.005). This hypoglycaemic action of both preparations administered in
equivalent daily dose appeared comparable. Glimepiride and glibenclamide stimulated
β-cell secretion and in the basal state both β-cell secretory products insulin and
C-peptide, were elevated in the plasma (basal C-peptide concentration: glimepiride
v. placebo, 0.79 ± 0.08 v. 0.68 ± 0.07 nmol/l, p < 0.01; glibenclamide v. placebo,
0.79 ± 0.07 v. 0.68 ± 0.07 nmol/l, p < 0.004). This insulinotropic effect appeared
to be comparable with no demonstrable difference in the efficacy of the two preparations.
Under steady-state hyperglycaemic conditions both agents promoted insulin release
(stimulated C-peptide concentration; glimepiride v. placebo, 1.39 ± 0.16 v. 1.11 ±
0.20 nmol/l, p < 0.006; glibenclamide v. placebo, 1.60 ± 0.18 v. 1.11 ± 0.20 nmol/l,
p < 0.001) and there was no statistically significant difference between active treatments.
Under steady-state euglycaemia both preparations continued to stimulate insulin release
as evidenced by the mean plasma C-peptide concentrations (glimepiridev. placebo, 0.69
± 0.10 v.0.28 ± 0.06 nmol/l, p < 0.01; glibenclamide v. placebo, 0.76 ± 0.12 v. 0.28
± 0.06 nmol/l, p < 0.01). Both glimepiride and glibenclamide had a comparable and
signifiant enhancing effect on glucose metabolism (Protocol II: M: glimepiride v.
placebo 4.4 ± 1.3 v. 1.3 ± 0.7 mg/kg · min, p < 0.05; glibenclamide v. placebo 4.7
± 1.3 v. 1.3 ± 0.7 mg/kg · min, p < 0.03) and improved tissue sensitivity to the action
of insulin as determined by the quantity of glucose metabolised per unit insulin (Protocol
II: M/I ratio: glimepiride v. placebo, 0.09 ± 0.03 v. 0.03 ± 0.01 kg · min per mU/l,
p < 0.02; glibenclamide v. placebo, 0.1 ± 0.03 v. 0.03 ± 0.01 kg · min per mU/l, p
< 0.01). In conclusion, glimepiride is a “second-generation” sulfonylurea agent which
stimulates pancreatic β-cell insulin secretion, lowers blood glucose and improves
tissue insulin sensitivity in non-insulin-dependent diabetic subjects. Its insulinotropic
effect is comparable with that of glibenclamide but may diminish in the presence of
normoglycaemia. The magnitude and hence, the clinical relevance of a selective beta-cytotropic
action, determined by blood glucose concentration, remains to be demonstrated.
Key words
Non-Insulin-Dependent Diabetes - Sulfonylurea - Glimepiride - Glibenclamide - Double-Blind,
Placebo-Controlled, Cross-Over Trial - Hyperglycaemic Glucose Clamp - Hyperinsulinaemic,
Euglycaemic Glucose Clamp - Insulin - C-Peptide
