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In vivo and in vitro studies exploring the pharmacokinetic interaction between bosentan, a dual endothelin receptor antagonist, and glyburide.

BACKGROUND: In a clinical trial with patients with chronic heart failure, a higher incidence of elevated levels of liver transaminases was observed during concomitant treatment with bosentan, a dual endothelin receptor antagonist, and glyburide (INN, glibenclamide), a sulfonylurea-type antidiabetic drug, than with treatment with bosentan alone. This study was conducted to investigate a possible pharmacokinetic interaction between bosentan and glyburide. METHODS: In a randomized, 2-way crossover study, 12 healthy volunteers received treatments A and B. Treatment A consisted of 125 mg bosentan twice a day for 10 days plus concomitant 2.5 mg glyburide twice a day on days 6 to 10. Treatment B consisted of 2.5 mg glyburide twice a day for 10 days plus concomitant 125 mg bosentan twice a day on days 6 to 10. Plasma concentrations of bosentan and its metabolites and of glyburide were measured on days 5 and 10 of treatment A and treatment B, respectively. RESULTS: Bosentan reduced the area under the concentration-versus-time curve of glyburide approximately 40% (P <.05). Glyburide decreased the area under the concentration-versus-time curve of bosentan and its metabolites 20% to 30% (P <.05). Results of in vitro experiments showed that glyburide is metabolized by cytochrome P450 (CYP) 2C9, 2C19, and 3A4. No interaction was observed on the level of serum protein binding. CONCLUSIONS: The plasma levels of both bosentan and glyburide were reduced after concomitant administration. This finding is consistent with a CYP3A4-inducing potential of both drugs. The observed pharmacodynamic interaction between bosentan and glyburide in patients with chronic heart failure cannot be explained by a pharmacokinetic interaction.

Adolescent↗

Evaluation of glipizide and glyburide in a health maintenance organization.

OBJECTIVE: To determine if there was a difference in the long-term glycemic control, average daily dose, and cost of therapy in patients with noninsulin-dependent diabetes mellitus (NIDDM) treated with glyburide and glipizide in a health maintenance organization (HMO). DESIGN: Retrospective evaluation of medical and pharmacy records. SETTING: Multispecialty group practice HMO. PATIENTS: 140 NIDDM patients being treated with either glyburide (n = 70) or glipizide (n = 70) were randomly selected from the populations of patients receiving either drug using computerized pharmacy records. MAIN OUTCOME MEASURE: Mean daily doses and blood glucose measurements (fasting blood glucose, random blood glucose, hemoglobin A1C) were stratified in 3-month periods from the time the drug therapy was started or the patient first presented to the clinic for a total of 18 months. Long-term glycemic control was defined as fasting blood glucose less than 8.33 mmol/L (150 mg/dL). RESULTS: The groups were comparable with regard to age (53.4 y glyburide, 56.7 y glipizide), gender (43 M:27 F glyburide, 47 M:23 F glipizide), race (38 W/16 B/16 H glyburide, 45 W/16 B/9 H glipizide), concurrent medical conditions, adverse effects, and compliance. Long-term glycemic control was similar in both groups. Although the number of subjects who were controlled (by definition) tended to be greater in the glyburide group, no clinical or statistical difference was found. There was no statistical difference in mean daily dose between the ethnic groups, but the small numbers preclude further analysis. The glipizide group had a larger percentage increase in dose within the first year than did the glyburide group; however, the percentage increase from the 3-month dose was similar after 18 months (22.7 percent glyburide, 27.5 percent glipizide.) Average daily cost of therapy, based on mean daily dose, was slightly lower for glyburide-treated patients. CONCLUSIONS: If glycemic control is similar with glyburide and glipizide, as seen in this study, economic considerations regarding choice of therapy and formulary inclusion may be appropriate.

Adult↗

Long-term safety of pioglitazone versus glyburide in patients with recently diagnosed type 2 diabetes mellitus.

STUDY OBJECTIVE: To evaluate the long-term safety and efficacy of glyburide versus pioglitazone in patients with a recent diagnosis of type 2 diabetes mellitus. DESIGN: Prospective, randomized, multicenter, double-blind trial with a 16-week titration period and a 40-week maintenance period. SETTING: Sixty-five investigative sites in the United States and Puerto Rico. PATIENTS: Five hundred two subjects with a recent diagnosis of type 2 diabetes that was unsuccessfully treated with diet and exercise were randomly assigned to study treatment. Of the 251 patients in each treatment group, 128 (51.0%) glyburide-treated patients and 134 (53.4%) pioglitazone-treated patients completed the study. INTERVENTIONS: Dosages of randomly assigned glyburide and pioglitazone were titrated every 4 weeks for 16 weeks in 5-mg/day and 15-mg/day increments, respectively, until a fasting plasma glucose level between 69 and 141 mg/dl was achieved. The optimized regimen was maintained during the subsequent 40-week double-blind phase. MEASUREMENTS AND MAIN RESULTS: At week 56, glyburide and pioglitazone improved glucose control comparably (change in hemoglobin A(1c) -2.02% and -2.07%, respectively, p=0.669). Withdrawal due to lack of efficacy or adverse events occurred more frequently with glyburide (20.8%) than pioglitazone (12.8%, p<0.032). Significantly higher percentages of glyburide- than pioglitazone-treated patients had a hypoglycemic (24.3% vs 4.4%, p=0.0001) or cardiac (8.8% vs 4.4%, p=0.0478) event. Edema (4.8% vs 7.9%, p=0.1443) and weight gain (4.4% vs 4.0%, p=0.8238) did not differ significantly between the glyburide and pioglitazone groups. Only a few patients discontinued study drug because of weight gain (one glyburide, one pioglitazone), edema (one pioglitazone), or a cardiac event (two glyburide). CONCLUSION: With long-term treatment, both glyburide and pioglitazone resulted in comparable glycemic control; however, pioglitazone was associated with less hypoglycemia and fewer withdrawals due to lack of efficacy or adverse events.

Adolescent↗

Comparison of pharmacokinetics, metabolic effects and mechanisms of action of glyburide and glipizide during long-term treatment.

Fourteen non-insulin-dependent diabetic (NIDDM) patients continued their previous medication (7 on glyburide, 7 on glipizide) for 6 mo, after which they switched to the alternate treatment for another 6 mo. The treatment periods were followed by 1 mo of placebo. The sulfonylurea dose was increased to achieve fasting plasma glucose levels less than 9 mM or to a total maximum daily dose of 25 mg. The mean final doses of glyburide (14.7 +/- 2.4 mg/day) and glipizide (15.2 +/- 2.2 mg/day) were similar. Postprandial (postdose) glipizide levels were higher than those of glyburide, whereas fasting (predose) glyburide concentrations were higher than those of glipizide. Both treatments improved glucose control by 25% compared with placebo. Glipizide therapy evoked higher postprandial insulin concentrations than did glyburide, whereas basal insulin concentrations were higher during glyburide. Insulin sensitivity, assessed by an insulin tolerance test, was more improved with glyburide than with glipizide. In conclusion, overall glucose control is similarly improved by glyburide and glipizide. However, glipizide amplifies the plasma insulin response to meals more than glyburide, whereas glyburide enhances basal insulin secretion more than glipizide. Both pharmacokinetic and pharmacodynamic factors may contribute to these differences.

Blood Glucose↗

Comparison of pharmacokinetics and pharmacodynamics of short- and long-term glyburide therapy in NIDDM.

OBJECTIVE: To examine the pharmacokinetics and pharmacodynamics of glyburide after single- and multiple-dose administration in patients with type II diabetes. RESEARCH DESIGN AND METHODS: Twenty patients with type II diabetes between 40 and 70 years of age participated in the study. A 24-h pharmacokinetic evaluation including a 4-h Sustacal tolerance test was conducted before instituting glyburide therapy (baseline), after the first 2.5-mg test dose of glyburide and at weeks 6 and 12 of chronic glyburide therapy. Glyburide doses were titrated with a target goal of achieving a fasting plasma glucose of < or = 7.8 mmol/l or to reach maximum daily doses of 20 mg. RESULTS: A significant prolongation in the elimination half-life (t1/2: week 0, 4.0 +/- 1.9 h; week 6, 13.7 +/- 10.5 h; and week 12, 12.1 +/- 8.2 h) and an increased volume of distribution of glyburide was observed during chronic dosing. These results strongly suggest possible drug accumulation. No differences in pharmacokinetic parameters were noted between evaluations at week 6 or week 12. Changes in pharmacodynamic response of glucose, insulin, and C-peptide to chronic glyburide therapy were observed. Glyburide therapy significantly reduced plasma glucose levels at weeks 6 and 12 (percent changes in AUC0-->4. glucose from baseline: week 0, -3 +/- 11%; week 6, -29 +/- 13%; and week 12, -26 +/- 19%). Pancreatic insulin secretion was acutely enhanced and maintained during long-term therapy. Responsiveness to therapy as assessed by the ratio of AUC0-->4.glucose:AUC0-->4.C-peptide was significantly improved at all weeks compared with baseline. No pharmacodynamic response differences were observed between the week 6 and the week 12 evaluations. CONCLUSIONS: This study demonstrates that significant differences in glyburide pharmacokinetics and pharmacodynamics exist between single-dose and steady-state conditions. These differences support the need for careful dosage titration of glyburide to achieve a desired therapeutic response in patients with type II diabetes.

Adult↗

Glyburide and glipizide, second-generation oral sulfonylurea hypoglycemic agents.

The chemistry, pharmacology, pharmacokinetics, clinical efficacy, adverse effects, and dosage of glyburide and glipizide, two second-generation oral sulfonylurea hypoglycemic agents, are reviewed. Glyburide and glipizide are well absorbed after oral administration. The absorption of glipizide is delayed by food; in contrast, glyburide absorption does not seem to be affected by administration with meals. Both drugs are extensively metabolized by the liver. A two-compartment open model adequately describes the pharmacokinetics of these drugs. The apparent elimination half-life of glyburide in oral dosage forms available in the United States ranges from 7 to 10 hours. Glipizide has a terminal elimination half-life of 2-7 hours. The effects of renal and hepatic disease on the pharmacokinetics of glyburide and glipizide have not been well studied. Based on controlled, comparative studies in patients with new-onset, diet-failed, Type II diabetes, glyburide appears to be at least as effective as chlorpropamide and tolazamide in controlling blood glucose. Glipizide has shown efficacy comparable to or greater than that of chlorpropamide and tolbutamide. Glyburide and glipizide appear to be comparable in terms of their ability to control fasting blood glucose in Type II diabetics. The recommended initial dosage of glyburide in newly diagnosed Type II diabetics is 2.5-5 mg once daily. For glipizide, the initial dosage should be 5 mg once daily. Elderly or debilitated patients and those with renal or hepatic impairment should be started on lower dosages initially. Glyburide and glipizide have adverse effects that are similar to those observed with the first-generation oral hypoglycemic agents. Glyburide and glipizide do not appear to offer major therapeutic advantages over first-generation oral sulfonylurea hypoglycemic agents. However, they may represent therapeutic alternatives for some patients who do not respond satisfactorily to other sulfonylureas.

Chemical Phenomena↗

Glyburide protein binding and the effect of albumin glycation in children, young adults, and older adults with diabetes.

Because glyburide is a weak acid that is more than 98% bound to albumin, the authors evaluated the binding in vitro and the influence of albumin glycation in children, young adults, and older adults with diabetes mellitus. Glyburide binding to non-glycated albumin was greater than 98%, and remained constant over a total concentration range of 50 to 1000 ng/mL. Increasing the albumin concentration from 0.5 to 5.0 g/dL was logarithmically related to the free fraction of glyburide. After the in vitro glycation of albumin (range, 5.7-15.6%), mean (+/- SD) glyburide binding was 99.05 +/- 0.082%, a value in agreement with that obtained from control serum. Serum samples from 57 subjects with type I and 16 patients with type II diabetes were incubated with 300 ng/mL of unlabeled glyburide and 200 ng/mL of 14C-glyburide. The extent of albumin glycation varied from 5 to 22% for the type I subjects and 5 to 14% for the type II subjects. The free fraction from these groups ranged from 1.07 to 1.75% and 0.66 to 0.88% for the type I and type II subjects, respectively. Although these values did not differ significantly from those of the control samples, the glyburide free fraction in patients with type I diabetes (1.39 +/- 0.85%) was significantly greater than that found for the 16 elderly patients with type II diabetes (0.78 +/- 0.05%). A significant linear relationship was not found between glyburide free fraction and the degree of albumin glycation for either group. Glyburide protein binding did not appear to be influenced by the extent of albumin glycation.

Adolescent↗

Increased muscle glucose uptake in response to chronic glyburide treatment is not related to changes in glucose transporter (GLUT4) protein.

1. The mechanism of action of glyburide (a sulfonylurea) on muscle has been investigated by measuring glucose uptake and glucose transporter (GLUT4) protein levels after chronic glyburide treatment. 2. A dietary induced insulin resistant rat model (4 wk of high-fat, high-sucrose feeding) was given glyburide (2 mg/kg/day) for 10 days and glucose uptake was measured in a perfused hindquarter preparation. 3. Protein levels of the GLUT4 glucose transporter were determined by Western analysis. 4. After 7 days of treatment, rats fed glyburide had lower blood glucose concentrations 2 hr (72 +/- 5 vs 103 +/- 12 mg/dl) and 24 hr (97 +/- 7 vs 123 +/- 7 mg/dl) after glyburide administration with no difference in serum insulin levels compared to vehicle treated animals. 5. Glucose uptake was approx doubled in basal state (0 insulin) in response to glyburide (2.8 +/- 0.4 vs 1.7 +/- 0.2 mumol/g per hr). 6. Maximal insulin (100 nM) stimulated glucose uptake tended to be higher in the glyburide treated group, but did not reach statistical significance (8.0 +/- 0.7 vs 7.0 +/- 0.6 mumol/g per hr). 7. Western analysis revealed no significant effect of glyburide on the GLUT4 protein level in skeletal muscle. 8. These results suggest that glyburide alters glucose uptake through some mechanism other than alterations in the level of the GLUT4 glucose transporter protein.

Animals↗

Effects of glimepiride and glyburide on glucose counterregulation and recovery from hypoglycemia.

Severe hypoglycemia, the most serious side effect of sulfonylurea therapy, has been reported to occur more frequently with glyburide than glimepiride. The present studies were undertaken to test the hypothesis that a differential effect on glucagon secretion may be involved. We performed hyperinsulinemic hypoglycemic (approximately 2.5 mmol/L) clamps in 16 healthy volunteers who received in randomized order placebo, glyburide (10 mg), and glimepiride (4 mg) just before beginning the insulin infusion and measured plasma glucagon, insulin, C-peptide, glucagon, epinephrine, cortisol, and growth hormone levels during the clamp and during a 3-hour recovery period after discontinuation of the insulin infusion. Neither sulfonylurea altered glucagon responses or those of other counterregulatory hormones (except cortisol) during the clamp. However, glyburide delayed plasma glucose recovery from hypoglycemia (plasma glucose at end of recovery period: control, 4.9 +/- 0.2 mmol/L; glyburide, 3.7 +/- 0.2 mmol/L; P = .0001; glimepiride, 4.5 +/- 0.2 mmol/L; P = .08). Despite lower plasma glucose levels, glyburide stimulated insulin secretion during this period (0.89 +/- 0.13 vs 1.47 +/- 0.15 pmol x kg(-1) x min(-1), control vs glyburide; P = .001), whereas glimepiride did not (P = .08). Short-term administration of glyburide or glimepiride did not alter glucagon responses during hypoglycemia. In contrast, during recovery from hypoglycemia, glyburide but not glimepiride inappropriately stimulates insulin secretion at low plasma glucose levels. This differential effect on insulin secretion may be an important factor in explaining why glyburide causes severe hypoglycemia more frequently than glimepiride.

Adult↗

Acceleration of stiffness in underperfused diabetic rat hearts by glyburide, a KATP channel blocker, and its prevention by levcromakalim and insulin.

OBJECT: To clarify the role of the KATP channels in myocardial dysfunction during underperfusion with norepinephrine (NE) in the diabetic heart, particularly the heart treated with sulphonylurea derivatives. METHODS: Isolated 6-week streptozotocin-diabetic rat hearts with a balloon in the left ventricle (LV) were paced and perfused with normoxic Krebs-Henseleit solution. Agents were infused for 15-25 min before as well as during 60-min underperfusion (2 ml/min/g heart weight) with 10(-6) M NE. Regional myocardial flow distribution was measured using dye microspheres. The effects of ex vivo glyburide (10(-6) M, a sulphonylurea anti-diabetic drug and a specific KATP channel inhibitor) on contractile dysfunction and abnormal regional myocardial energy metabolism were examined during underperfusion with NE in the absence of presence of levcromakalim (10(-4) M, a selective K+ channel opener) and insulin (2 mU/min/g heart weight). RESULTS: The flow rate was greater in the LV subendocardium than the subepicardium during normal perfusion, and smaller at 60-min underperfusion with NE. The LV diastolic tension and pressure during underperfusion with NE increased more rapidly in the presence of glyburide. At 60-min underperfusion with NE, the diastolic pressure elevation was still higher in the glyburide-treated heart, and decreases in tissue ATP, creatine phosphate (CP), energy charge, phosphorylation potential and CP/inorganic phosphate (P(i)) ratio, and increases in AMP, P(i) and lactate were more marked in the glyburide-treated heart, particularly in the LV subendocardium. Thus, ex vivo glyburide enhanced the increase in LV stiffness and abnormal myocardial energy metabolism during underperfusion with NE in diabetic hearts. These changes were reduced by levcromakalim to the level during underperfusion with NE without glyburide. Insulin did not prevent the glyburide-induced earlier exacerbation of the increase in LV stiffness during underperfusion with NE, but reduced the detrimental effects 20 min after the onset of underperfusion. CONCLUSIONS: KATP channels in the diabetic myocardium probably open during underperfusion with NE, and it helps delay the initiation of the increase in cardiac stiffness. Glyburide may have harmful effects in the ischemic diabetic heart; the myocardial KATP channel blockade during underperfusion with NE enhanced the increase in LV stiffness and abnormal myocardial energy metabolism. The glyburide-induced detrimental effects in the ischemic diabetic heart are prevented by levcromakalim and partly by insulin.

Animals↗

Glyburide decreases myocardial oxygen pressure in dogs.

BACKGROUND: Reports show that glyburide, an adenosine triphosphate sensitive potassium (K+ATP) channel blocker, will reverse the myocardial protective effect of inhalational anesthesia. We evaluated the effect of glyburide on myocardial tissue oxygen pressure (PmO2) in dogs anesthetized with desflurane. METHODS: Twelve dogs were anesthetized with 8% end-tidal desflurane for baseline anesthesia. A flow probe was placed on the left anterior descending (LAD) artery. A probe that measured PmO2 was inserted into the middle myocardium in the LAD region. After baseline measures, six dogs received i.v. 1 mg kg(-1) of glyburide and six dogs received sham vehicle treatment. After the glyburide or sham treatment, each dog received an i.v. infusion of adenosine 0.1 microg kg(-1) x min(-1), sodium nitroprusside (SNP) 2-4 microg kg(-1) x min(-1) and 14% end-tidal desflurane in random order. RESULTS: Glyburide decreased LAD artery flow from 59 +/- 9 ml min(-1) to 30 +/- 6 ml min(-1) (P < 0.05) and PmO2 from 44 +/- 16 mmHg to 30 +/- 9 mmHg (P < 0.05). Adenosine infusion increased LAD artery blood flow 180% in the sham-treated dogs but produced no change in the glyburide-treated dogs. Sodium nitroprusside infusion increased LAD artery flow and decreased PmO2 in both the glyburide- and sham-treated dogs. Desflurane (14%) did not reverse the glyburide-induced vasoconstriction but increased PmO2 to 38 +/- 20 mmHg (P < 0.05). CONCLUSION: Glyburide produced myocardial tissue hypoxia, which was not changed by adenosine, worsened by SNP and improved by 14% desflurane. The improvement in PmO2 with desflurane occurred without a change in myocardial blood flow.

Adenosine↗

Prospective observational study to establish predictors of glyburide success in women with gestational diabetes mellitus.

OBJECTIVE: To establish parameters associated with therapeutic success in gestational diabetics treated with glyburide. STUDY DESIGN: A total of 69 gestational diabetics who failed dietary therapy were treated with glyburide. Inadequate glycemic control on maximum dose glyburide (10 mg b.i.d.) was considered treatment failure. The glyburide failure rate was calculated and factors that might predict success with glyburide were analyzed between the success and failure groups using chi(2) or Student'st-tests. RESULTS: The glyburide failure rate was 18.8%. Gestational age at glyburide initiation (p<0.01), pretreatment fasting blood sugars (p<0.001), and 1-hour postprandial values (p<0.001) were the only statistically significant factors between the two groups. Glyburide success was predicted if dietary failure occurred after 30 weeks, or fasting blood sugars were <110 mg/dl and 1-hour postprandials were <140 mg/dl (sensitivity 98%, specificity 65%). CONCLUSION: Gestational diabetics who fail dietary therapy after 30 weeks gestation or have fasting blood sugars <110 mg/dl and 1-hour postprandials <140 mg/dl do well on glyburide therapy.

Adult↗

Glyburide-stimulated glucose transport in cultured muscle cells via protein kinase C-mediated pathway requiring new protein synthesis.

To study the mechanism of action of sulfonylurea agents on peripheral tissues without the potentially confounding influences of insulin, the direct effect of glyburide (i.e., in the absence of insulin) was evaluated in the L6 cultured myogenic cell line. Glyburide approximately doubled the incorporation of [14C]-glucose into glycogen. The rate-determining enzymes of glycogen metabolism, glycogen synthase and glycogen phosphorylase, were unaffected by the drug. Glucose transport (2-deoxyglucose uptake) was also approximately doubled. The phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) also doubled glucose transport and showed the same lag period (4-6 h) as glyburide before an effect occurred. Blockade of protein kinase C activity by either 1-(5-isoquinolinesulfonyl)-2 methyl piperazine (H7) or chronic exposure to TPA completely abolished the stimulation by glyburide. Cycloheximide, a protein synthesis inhibitor, also completely eliminated the effect of glyburide. The presence of ATP-sensitive K+ channels was assessed by measuring 86Rb efflux in ATP-depleted L6 muscle cells and RINm5F cells (which served as a positive control). Such channels were present and responded appropriately to glyburide and diazoxide in pancreatic beta-cells but were not present in muscle cells. Glyburide stimulation of glucose transport was completely eliminated by both Quin 2, an intracellular chelator of Ca2+, and verapamil, a Ca2+ channel blocker. However, glyburide did not raise intracellular Ca2+ levels. We conclude that glyburide stimulates glucose transport in cultured L6 muscle cells by a protein kinase C-mediated pathway that requires new protein synthesis. Although intracellular Ca2+ metabolism may also be involved, the initial step in the mechanism of action is probably different between pancreatic beta-cells and muscle cells.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗

Slow elimination of glyburide in NIDDM subjects.

OBJECTIVE: To determine the terminal elimination half-life of glyburide in non-insulin-dependent diabetes mellitus (NIDDM) subjects after cessation of long-term treatment. RESEARCH DESIGN AND METHODS: Ten NIDDM patients (5 of each sex, 36-72 years old, without hepatic or renal disease) taking a median glyburide dose of 14 mg/day, who were to start insulin therapy because of sulfonylurea failure, were studied. Serum glyburide concentrations, measured by a newly developed selective and sensitive liquid chromatographic method, were followed from 10 to 48 h after the last glyburide dose. RESULTS: Serum glyburide levels declined in three different phases, with a terminal gamma-phase between 18 and 48 h having a mean +/- SD half-life of 15.0 +/- 6.7 h. Two patients had half-lives over 20 h. The half-life values did not correlate with fasting blood glucose, age, body weight, body mass index, or creatinine levels. The latter agrees with the assumption that glyburide is completely eliminated by metabolic transformation. Although longer than previously observed, the current half-life values are in accordance with clinical experience that glyburide is a long-acting sulfonylurea. CONCLUSIONS: The elimination of glyburide in NIDDM subjects is slower than previously reported. The long half-life adds support to the use of a once-daily dosage of glyburide. It also justifies increased caution when using this sulfonylurea.

Adult↗

Importance of early insulin secretion: comparison of nateglinide and glyburide in previously diet-treated patients with type 2 diabetes.

OBJECTIVE: This study compared the effects of nateglinide, glyburide, and placebo on postmeal glucose excursions and insulin secretion in previously diet-treated patients with type 2 diabetes. RESEARCH DESIGN AND METHODS: This randomized, double-blind, placebo-controlled multicenter study was conducted in 152 patients who received either nateglinide (120 mg before three meals daily, n = 51), glyburide (5 mg q.d. titrated to 10 mg q.d. after 2 weeks, n = 50), or placebo (n = 51) for 8 weeks. Glucose, insulin, and C-peptide profiles during liquid meal challenges were measured at weeks 0 and 8. At weeks -1 and 7, 19-point daytime glucose and insulin profiles, comprising three solid meals, were measured. RESULTS: During the liquid-meal challenge, nateglinide reduced the incremental glucose area under the curve (AUC) more effectively than glyburide ( = -4.94 vs. -2.71 mmol. h/l, P < 0.05), whereas glyburide reduced fasting plasma glucose more effectively than nateglinide ( = -2.9 vs. -1.0 mmol/l, respectively, P < 0.001). In contrast, C-peptide induced by glyburide was greater than that induced by nateglinide ( = +1.83 vs. +0.95 nmol. h/l, P < 0.01), and only glyburide increased fasting insulin levels. During the solid meal challenges, nateglinide and glyburide elicited similar overall glucose control ( 12-h incremental AUC = -13.2 vs. -15.3 mmol. h/l), but the insulin AUC induced by nateglinide was significantly less than that induced by glyburide ( 12-h AUC = +866 vs. +1,702 pmol. h/l, P = 0.01). CONCLUSIONS: This study demonstrated that nateglinide selectively enhanced early insulin release and provided better mealtime glucose control with less total insulin exposure than glyburide.

Aged↗

Pharmacokinetics and pharmacodynamics of glyburide in young and elderly nondiabetic adults.

The pharmacokinetics and pharmacodynamics of glyburide were studied in elderly and young nondiabetic adults. Healthy nondiabetic men and women 18-40 years of age (young subjects) and 60-85 years of age (elderly subjects) were recruited. After an overnight fast, the subjects were given a baseline glucose tolerance test (GTT). The next day, again after a fast, each subject was given a 5-mg oral tablet of glyburide, and the GTT was performed one hour later. Serum glucose, serum insulin, and plasma glyburide concentrations were determined. Twenty elderly (mean +/- S.D. age, 65.7 +/- 5.3 years) male (n = 10) and female (n = 10) volunteers and 15 young (22.3 +/- 4.5 years) male volunteers were enrolled. Compared with the young subjects, the elderly subjects had slower glyburide absorption, as determined from a lower peak plasma concentration and smaller area under the plasma concentration-time curve from zero to four hours (AUC0-4). The elderly subjects also had a lower glyburide elimination rate constant and higher volume of distribution and a 52% higher free fraction. There was no difference in the glyburide AUC0-24 or AUC0-infinity or in oral clearance between the groups. The elderly group had greater increases in serum glucose and insulin concentrations after the baseline GTT. After glyburide administration, the elderly group had a smaller fractional decrease in the glucose AUC0-3 from the baseline GTT result than the young subjects. Linear regression analysis of the relationship between the fractional change in glucose concentration and the glyburide AUC0-4 showed significantly different slopes between the two groups. The aging process appears to affect the pharmacokinetics and pharmacodynamics of glyburide.

Adolescent↗

Cellular mechanism of glyburide-induced insulin gene expression in isolated rat islets.

The cellular mechanism for the effects of glyburide on the synthesis and release of insulin and insulin gene expression in isolated islets was investigated. On incubation for 1 h, glyburide increased insulin release without affecting either the insulin content or the PPI mRNA level. H-7, an inhibitor of PKC, inhibited the glyburide-induced insulin release, while H-8, an inhibitor of cyclic nucleotide-dependent protein kinases, did not affect the glyburide-induced insulin release. On incubation for 20 h, glyburide increased insulin release and the PPI mRNA level, without affecting the insulin content. H-7 inhibited glyburide-induced insulin release and increased the PPI mRNA level. H-8 significantly inhibited both the glyburide-induced increase in insulin release and increase in PPI mRNA level. In conclusion, glyburide stimulated insulin release via a PKC-mediated pathway and increased the PPI mRNA level via cyclic nucleotide-dependent protein kinase(s).

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗

Effects of glyburide on in vivo insulin-mediated glucose disposal.

The purpose of this study was to examine the effects of glyburide on peripheral (muscle) and hepatic insulin sensitivity in patients with non-insulin-dependent diabetes mellitus (NIDDM) and insulin-dependent diabetes mellitus (IDDM) as well as in healthy control subjects. In protocol 1, 10 patients with NIDDM and seven young healthy control subjects were studied. Changes in insulin sensitivity (40 mU/m2.min euglycemic insulin clamp), hepatic glucose production (3-[3H]glucose turnover), and insulin secretion (+125 mg/dL hyperglycemic clamp) were measured before and after 3 months (in patients with NIDDM) and 6 weeks (in young control subjects) of glyburide therapy. In protocol 2, five patients with IDDM and eight patients with insulin-treated NIDDM were evaluated before and after two months of glyburide therapy (20 mg per day). Changes in daily insulin requirements, 24-hour plasma glucose profiles, glycohemoglobin, glucagon-stimulated C-peptide secretion, insulin sensitivity, and hepatic glucose production were measured. In protocol 1, glyburide significantly improved insulin sensitivity (p less than 0.01) and insulin secretion (p less than 0.01) in the NIDDM patients. The elevated rates of hepatic glucose production (2.4 +/- 0.3 mg/kg.min) were reduced after glyburide therapy (1.7 +/- 0.2 mg/kg.min; p less than 0.01) and were highly correlated with an improvement in fasted plasma glucose levels (r = 0.92; p less than 0.001). Insulin sensitivity also improved in the young healthy control subjects after glyburide therapy (6.5 +/- 0.5 to 7.6 +/- 0.7 mg/kg.min; p less than 0.05). In protocol 2, glyburide treatment produced no change in daily insulin requirement (54 +/- 8 versus 53 +/- 7 units per day), mean 24-hour glucose levels (177 +/- 20 versus 174 +/- 29 mg/dL), glycohemoglobin (10.1 +/- 1.0 percent versus 9.5 +/- 7 percent), C-peptide secretion, insulin sensitivity, or basal hepatic glucose production (p values not significant) in the IDDM patients. In contrast, the insulin-treated NIDDM patients had significant reductions in mean daily insulin requirement (72 +/- 6 versus 58 +/- 9 units per day; p = 0.05), mean 24-hour plasma glucose levels (153 +/- 10 to 131 +/- 5 mg/dL; p less than 0.05), and glycohemoglobin levels (10.3 +/- 0.7 percent to 8.0 +/- 0.4 percent; p less than 0.05) and an improvement in C-peptide secretion (0.24 +/- 0.07 to 0.44 +/- 0.09 pmol/mL; p = 0.08). Stimulated C-peptide levels were highly correlated with a reduction in insulin dose observed during the 2-month treatment period (r = 0.93; p less than 0.001). Insulin sensitivity improved slightly but not significantly after glyburide treatment.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗