Improved effect of glibenclamide on administration before breakfast

Oral Agents for the Treatment of Gestational Diabetes

PURPOSE OF REVIEW

To review the current evidence of the safety and efficacy of the use of oral agents for treatment of gestational diabetes (GDM).

RECENT FINDINGS

The use of metformin and glyburide in pregnancy for treatment of GDM has dramatically increased since the early 2000s. Meta-analyses suggest that glyburide may increase the risk for large for gestational (LGA) infants and neonatal hypoglycemia. Conversely, metformin may potentially decrease rates of pregnancy-induced hypertension, LGA, neonatal hypoglycemia, and maternal weight gain. However, recent long-term offspring studies indicate a potential detrimental effect of metformin on fat mass that suggests an effect of such medication on fetal programming. While there have been several novel oral anti-diabetes medications brought to market in the past decade, there is minimal data to guide use and in particular data regarding long-term safety for the exposed offspring of treated women. Most professional societies recommend insulin as first-line treatment of gestational diabetes after failure of lifestyle modification. Both metformin and glyburide cross the placenta and long-term safety data is limited. However, patient satisfaction is substantially higher with use of oral agents, and the current literatures suggest that metformin may reduce several common short-term adverse outcomes related to GDM.

A pharmacologic approach to the use of glyburide in pregnancy

Despite widespread use of glyburide to treat pregnancy-related hyperglycemia, the dosing regimen is based in large part on pharmacokinetic and pharmacodynamic studies in men and nonpregnant women. Like many medications used by pregnant women, adequate pharmacokinetic and pharmacodynamic data in pregnancy have been sorely lacking. This lack of information can lead to both overdosing with excessive side effects and underdosing with an inadequate therapeutic response. Both of these problems may apply to glyburide use in pregnancy. This commentary provides a pharmacologic basis for altering the glyburide administration regimen. Taking glyburide 1 hour before a meal may improve efficacy in patients with pregnancy-related hyperglycemia.

Control of postprandial hyperglycemia: optimal use of short-acting insulin secretagogues

OBJECTIVE

This study was designed to compare the efficacy of acute premeal administration of glipizide versus nateglinide in controlling postprandial hyperglycemia in subjects with non-insulin-requiring type 2 diabetes.

RESEARCH DESIGN AND METHODS

A total of 20 subjects (10 female, 10 male) with non-insulin-requiring type 2 diabetes were admitted overnight to the General Clinical Research Center on four occasions. In random order, 10 mg glipizide (30 min premeal), 120 mg nateglinide (15 min premeal), 10 mg glipizide plus nateglinide (30 and 15 min premeal, respectively), or placebo pills (30 and 15 min premeal) were administered in a double-blind fashion before a standardized breakfast. Blood was drawn for analysis of glucose, insulin, and C-peptide at -0.05, 0, 0.5, 1, 2, 3, and 4 h relative to the meal.

RESULTS

The subjects were aged 56 +/- 2 years and were moderately obese (BMI 31 +/- 1 kg/m(2)), with a mean HbA(1c) of 7.4 +/- 0.4%. The peak postprandial glucose excursion above baseline was higher with placebo (6.1 +/- 0.5 mmol/l) than glipizide (4.3 +/- 0.6 mmol/l, P = 0.002), nateglinide (4.2 +/- 0.4 mmol/l, P = 0.001), or glipizide plus nateglinide (4.1 +/- 0.5 mmol/l, P = 0.001). The area under the curve for the glucose excursion above baseline was also higher with placebo (14.1 +/- 1.8 mmol/h. l) compared with glipizide (6.9 +/- 2.4 mmol/h. l, P = 0.002), nateglinide (9.7 +/- 2 mmol/h. l, P = 0.004), or glipizide plus nateglinide (5.6 +/- 2.2 mmol/h. l, P < 0.001). Peak and integrated glucose excursions did not differ significantly between glipizide and nateglinide. However, by 4 h postmeal, plasma glucose levels were significantly higher with nateglinide (9 +/- 0.9 mmol/l) compared with the premeal baseline (7.8 +/- 0.6 mmol/l, P = 0.04) and compared with the 4-h postprandial glucose level after administration of glipizide (7.6 +/- 0.6 mmol/l, P = 0.02). Integrated postprandial insulin levels were higher with glipizide (1,556 +/- 349 pmol/h. l) than nateglinide (1,364 +/- 231 pmol/h. l; P = 0.03). Early insulin secretion, as measured by insulin levels at 30 min postmeal, did not differ between glipizide and nateglinide.

CONCLUSIONS

Acute premeal administration of nateglinide or glipizide has equal efficacy in controlling postbreakfast hyperglycemia in type 2 diabetes when each drug is administered at the optimum time before the meal. Glipizide causes a more pronounced and sustained postmeal insulin secretory response compared with nateglinide. Glipizide facilitates the return to near-fasting glucose levels at 4 h postmeal, but with the possible risk of increased frequency of postmeal hypoglycemia in drug-naive patients. The clinical decision to use glipizide versus nateglinide should be based on factors other than the control of postprandial hyperglycemia in type 2 diabetes.

[Present status in the treatment of type 2 diabetes mellitus. Insulin-secreting agents]

The functional defect of the pancreatic beta cell represents one of the main therapeutic targets in type 2 diabetes mellitus. Among the currently available oral antidiabetic drugs, only hypoglycaemic sulfonylureas exhibit beta cell stimulating properties. However, their use has some limits, particularly those related to the risk of hypoglycaemia and the frequent secondary therapeutic failure. These drugs have largely contributed to the knowledge of the mechanisms of insulin secretion. Besides some galenic modifications of existing sulfonylureas and the development of new drugs of this family with original properties, like glimepiride, the research is essentially focused on drugs derived from the non sulfonylurea moiety of some sulfonylureas, particularly the meglitinide family, which will probably be available for the clinician in the near future. These drugs act however grossly by the same mechanism than sulfonylureas, even if their binding site on a protein coupled with the ATP sensitive K channel appears different. Among the other possible approaches suggested by the theoretical data concerning the mechanisms of insulin secretion, GLP-1 derivatives probably represent good candidates, if stable analogues are developed.

Is there a concentration-effect relationship for sulphonylureas?

Sulphonylureas have remained the mainstay of oral therapy for type 2 (non-insulin-dependent) diabetes mellitus (NIDDM). They stimulate insulin release from pancreatic beta cells. Pharmacokinetic differences between the various sulphonylureas are of clinical importance in terms of the time to onset of action, timing of drug administration in relation to food intake, magnitude and duration of the glucose-lowering effect and the risk of serious hypoglycaemia. Recent studies with improved analytical sensitivity have shown that the elimination half-life of glibenclamide is longer than previously thought and that 2 metabolites of glibenclamide have significant hypoglycaemic activity. Furthermore, single dose studies in healthy volunteers using an integrated pharmacokinetic-pharmacodynamic model have identified clear concentration-effect relationships for both glibenclamide and its metabolites after oral and intravenous administration. Under multiple dose conditions, kinetic-dynamic relations have been identified with shorter-acting drugs in dosages that give discontinuous sulphonylurea exposure. However, at continuous exposure, i.e. sustained 24-hour therapeutic concentrations in plasma, there is evidence indicating the development of tolerance, which may be caused by downregulation of beta cell sensitivity. As more sophisticated concentration-effect studies appear, it has become evident that currently recommended maximum daily doses of many sulphonylureas are too high.

Sulfonylureas

Sulfonylureas have been available for the treatment of non-insulin-dependent diabetes mellitus (NIDDM) since the 1950s. With the introduction of new oral agents, there is a tendency to discount the value of sulfonylurea therapy. Sulfonylureas have the advantage of multiple formulations, low costs, minimal side effects, and demonstrated efficacy in controlling hyperglycemia. The major disadvantage of sulfonylureas is secondary failure, which may occur with all oral agents as part of the progression of NIDDM. Sulfonylureas should continue to play an important role in the treatment of NIDDM.

The effect of the timing and the administration of acarbose on postprandial hyperglycaemia

To clarify the optimum timing for ingestion of acarbose, a 100 mg dose of this oral hypoglycaemic agent was administered 30 min before, at the beginning, and 15 min after ingestion of a test meal, and the effects of the drug on blood glucose rises were compared with increases observed after a control meal (no drug). Twenty-four patients with Type 2 diabetes were included in a randomized, open, cross-over study. The smallest increases in blood glucose (p < 0.001) occurred when acarbose was taken at the beginning and 15 min after starting the test meal (3.3 +/- 1.6 mmol l-1 and 3.3 +/- 1.4 mmol l-1). The increase in blood glucose levels when acarbose was taken 30 min before the test meal was significantly higher (4.2 +/- 1.8 mmol l-1) and it was at its maximum following the control meal (5.2 +/- 1.7 mmol l-1). Similar results were observed when the effects of acarbose on insulin and C-peptide levels were measured. It is recommended that patients should be instructed to take acarbose with their first mouthful of food.

The effects of magnesium hydroxide on the absorption and efficacy of two glibenclamide preparations

1. The effect of magnesium hydroxide on the absorption and efficacy of two glibenclamide preparations was investigated in healthy volunteers in two separate studies, using a randomized cross-over design with two phases. 2. A single dose of magnesium hydroxide (850 mg) or water only (150 ml) was given immediately after the ingestion of a micronised (1.75 mg, seven subjects) or a non-micronised (2.5 mg, six subjects) preparation of glibenclamide. Plasma concentrations of glibenclamide, insulin and glucose were measured. 3. Magnesium hydroxide accelerated (P less than 0.05) the absorption of glibenclamide from the micronised preparation to a small extent but the extent of absorption and the insulin and glucose responses were unaltered. 4. Coadministration of magnesium hydroxide with the non-micronised glibenclamide preparation increased the area under the plasma glibenclamide concentration-time curve from 0 to 3 h, five-fold (P less than 0.05), the total area three-fold (P less than 0.05) and the peak drug concentration three-fold (P less than 0.05). The incremental insulin area from 0 to 3 h was increased 35-fold (P less than 0.05) and the maximum insulin response 10-fold (P less than 0.05) by magnesium hydroxide. 5. Concomitant ingestion of magnesium hydroxide and non-micronised glibenclamide may greatly enhance the absorption and efficacy of glibenclamide. The absorption of micronised glibenclamide appears to be only slightly influenced by magnesium hydroxide.

Pharmacokinetic and pharmacodynamic studies of glibenclamide in non-insulin dependent diabetes mellitus

1. The pharmacokinetic and pharmacodynamic properties of oral glibenclamide have been studied in 31 hospitalised in-patients and 79 ambulant out-patients with diabetes mellitus. 2. Breakfast was found to have no significant influence on the kinetic behaviour of glibenclamide or on the effect of this drug on blood glucose utilisation. 3. The time course of glibenclamide kinetics after 20 mg dosing was adequately described by a two-compartment open model, yielding mean half-lives of 3.3 +/- 1.5 h (t1/2, lambda 1) and 9.7 +/- 1.2 (t1/2, z) for the initial and terminal elimination phases respectively. 4. No significant accumulation or change in kinetic profile occurred in patients who had normal renal and hepatic function, were treated continuously with glibenclamide, and then rechallenged after 8-12 weeks. 5. Despite inter-individual variations in drug absorption, peak plasma concentrations (Cmax) and the area under the plasma concentration-time curve (AUC(0-24] were dose-dependent over the dose range 5-20 mg. No significant dose-response behaviour was observed in respect of glucose utilisation, suggesting that there is little clinical benefit in using doses of glibenclamide above 5 mg day-1. 6. Comparison of plasma glibenclamide concentrations at different time-bands following doses of 5 and 10 mg showed a wider range in ambulant out-patients than in age-, sex-matched in-patients treated with the same dosages of drug. Mean plasma drug concentrations attained at all time bands up to 8 h after dosing were higher in out-patients than in in-patients, suggesting a tendency to 'over-compliance' by patients in anticipation of attendance at clinic.

The effects of ingestion time of gliclazide in relationship to meals on plasma glucose, insulin and C-peptide levels

The effect of altering the timing of gliclazide administration in relation to a meal was studied in ten type 2 (non-insulin dependent) chronically treated diabetics. Gliclazide was given 30 min before, at the start of and 30 min after breakfast or omitted altogether. Plasma gliclazide was present at greater than 2 mg/l throughout the study periods. Administration at 30 min after the meal significantly delayed the time to peak for plasma gliclazide. No significant difference was noted in plasma glucose, insulin or c-peptide patterns with any protocol. It is concluded that, in clinical practice, with chronically treated diabetics the timing of gliclazide ingestion in relation to meals is not critical.

Sulphonylurea antidiabetic drugs. An update of their clinical pharmacology and rational therapeutic use

Apart from the amelioration of symptoms, a major aim of the treatment of non-insulin-dependent diabetes mellitus (NIDDM, type 2 diabetes) should be the prevention of cardiovascular complications. These are associated with the chronic hyperglycaemia that is characteristic of NIDDM, and the risk of complications is already increased in subjects with impaired glucose tolerance (IGT). For these reasons, and because hyperglycaemia appears to be a self-perpetuating condition, treatment should be introduced as early as possible and should be aimed at normalisation of blood glucose. To enable early detection and intervention, screening is necessary. As diet regulation alone rarely suffices to normalise blood glucose, addition of sulphonylurea drugs is indicated in many cases. If introduced in the IGT phase, sulphonylureas drugs combined with diet regulation may postpone the development of IGT to manifest NIDDM, and may reduce the increased risk of cardiovascular morbidity and mortality. Sulphonylureas stimulate insulin release, possibly via interaction with receptors in the pancreatic B cells. In addition, such treatment enhances the reduced insulin action. This might be a primary effect but is also a consequence of the increased access to insulin and the subsequent reduction of hyperglycaemia. Sulphonylureas may enhance insulin availability by reducing insulin clearance. Effects on blood lipids are probably secondary phenomena. Fast and short acting sulphonylureas may improve the impaired meal-induced acute insulin release. If combined with weight-reducing diet regulation and introduced early, such treatment can maintain (near) normal blood glucose levels and an improved insulin action for several years without increasing basal insulin secretion, without chronic hyperinsulinaemia, and without weight increase. If not combined with diet regulation, sulphonylurea therapy is likely to fail. If introduced when NIDDM is advanced, the efficacy of these drugs is limited, with secondary failures developing at a rate of 5 to 10% per year. Continuous (24-hour-a-day) exposure to drug treatment could possibly desensitise the B cell to sulphonylurea stimulation. 'Second-generation' sulphonylurea drugs have a higher potency than 'first-generation' drugs, but this need not signify a greater clinical efficacy. The effect of several of these drugs may be increased if they are ingested half an hour before meal(s). Short acting sulphonylureas may be safer than long acting ones, which seem more likely to cause long lasting and fatal hypoglycaemia, at least in elderly patients.(ABSTRACT TRUNCATED AT 400 WORDS)

The relationship between the pharmacokinetics and pharmacodynamic effects of oral hypoglycaemic drugs

Oral hypoglycaemic drugs have widely differing pharmacokinetic properties. Possible pharmacodynamic benefits include greater efficacy and fewer adverse effects. In general, it has not been possible to demonstrate unequivocal differences in clinical efficacy between the sulphonylureas during long term use, although there are clear differences in potency. These differences have been emphasised to the extent that the term 'second-generation' has been used for the most potent sulphonylureas, but there is little to suggest that potency is of any therapeutic significance. Trials to study differences in efficacy have rarely been of acceptable design. They have often used fixed doses of drugs, begging the question of whether true potency ratios have been established for chronic treatment. They have rarely involved substantial numbers of patients in double-blind crossover studies with a suitable washout period. Trials which show that there is a clear relationship between drug concentrations in blood and drug effects (whether therapeutic effects or adverse effects such as severe hypoglycaemia) are generally lacking. Qualitative and semiquantitative analysis of adverse effects supports the concept that drugs with a long half-life (e.g. chlorpropamide), renally excreted active metabolites (e.g. acetohexamide) or unusual properties (e.g. glibenclamide, which accumulates progressively in islet tissue) are more likely to cause prolonged hypoglycaemia, which may be fatal. The major adverse effect of treatment with biguanides is lactic acidosis, and this probably occurs more commonly in patients treated with phenformin than those treated with metformin because of pharmacogenetic variation in phenformin metabolism. The available evidence therefore favours the use of drugs with a short elimination half-life which are extensively metabolised and which have no active metabolites.

Clinical pharmacology of sulfonylureas

Sulfonylureas seem to have similar mechanisms of action, including an acceleration and increase of insulin secretion, an increase of the systemic availability of insulin, and probably indirectly, an increase of insulin action. Sulfonylureas may postpone the development of impaired glucose tolerance (IGT) to manifest non-insulin-dependent diabetes mellitus (NIDDM), and all NIDDM subjects should benefit from sulfonylurea treatment except those in whom insulin secretion has been attenuated. The most effective use is the combination of diet restriction and sulfonylurea introduced in NIDDM subjects soon after transition from IGT to NIDDM. A simple screening procedure has been devised to find the subjects at this early stage. Newer sulfonylureas, such as glipizide and glyburide, are more potent than the older ones, such as tolbutamide and chlorpropamide. During chronic treatment, glipizide and glyburide seem to be equally effective in reducing blood glucose levels, and they do so without causing a chronic elevation of insulin secretion, signifying that they do not increase the risk of pancreatic B cell exhaustion. Glipizide has rapid and complete absorption, as well as a rapid distribution and elimination. This may explain why it is less liable than other sulfonylureas to provoke long-lasting hypoglycemia, which is the major danger when using sulfonylureas. Despite its rapid elimination, 7.5 to 15 mg glipizide can be administered once daily without loss of therapeutic efficacy. This may be due in part to enterohepatic recirculation of the drug in response to meals. The therapeutic efficacy is increased if glipizide is received half an hour before breakfast.

Potentiation by previous nutrients of glibenclamide-induced insulin release in man. An effect which is counteracted by meal-induced retardation of drug absorption

We have studied the impact of a previous meal on insulin and glucose responses to the subsequent administration of glibenclamide. Healthy volunteers and NIDDM patients ingested a standard low-carbohydrate breakfast, and glibenclamide was administered 110-120 min later either as an intravenous bolus (12.5 micrograms/kg body wt), or as a tablet (5 mg HB 419). When glibenclamide was administered i.v. the drug raised insulin and lowered blood glucose levels, and previous breakfast potentiated these effects both in healthy volunteers and in NIDDM patients. Conversely when glibenclamide was given as a tablet the drug per se raised C-peptide and lowered blood glucose levels under fasting conditions, whereas the drug had no effect when ingested after breakfast. Measurements of glibenclamide in plasma revealed that previous breakfast delayed the systemic appearance of ingested glibenclamide. We conclude that nutrients sensitize insulin-releasing cells to subsequent stimulation by glibenclamide, thereby aggravate a blood-glucose-lowering effect of the drug. However this effect, which could potentially induce undesirable hypoglycaemia in sulphonylurea-treated diabetics, is counteracted when glibenclamide is taken orally because of a meal-induced decrease in drug absorption.

Review of glyburide after one year on the market

After one year on the American market, glyburide, a second-generation sulfonylurea, seems well accepted by physicians. If the hyperglycemia of patients with type II diabetes mellitus is not corrected by diet and exercise, glyburide can be used as adjunctive therapy. The drug is comparable in efficacy to the first-generation sulfonylurea chlorpropamide, but it has fewer reported side effects. Additionally, glyburide does not appear to interact with other medications and is well absorbed from the gastrointestinal tract. Although the drug had been reported to produce hypoglycemia, increased clinical experience--along with use of judicious dosages in appropriate patients--has decreased the incidence of hypoglycemia. Although still in the investigational stage, combination insulin/glyburide therapy may also benefit subgroups of type II diabetic patients. Glyburide is a useful and rational addition to therapy in properly selected patients with type II diabetes mellitus.

Glyburide: a second-generation sulfonylurea hypoglycemic agent. History, chemistry, metabolism, pharmacokinetics, clinical use and adverse effects

Glyburide, a second-generation hypoglycemic sulfonylurea, is 200 times as potent as tolbutamide. This increase is due to greater intrinsic hypoglycemic potency of the molecule rather than to a prolonged biologic half-life. Glyburide is inactivated by the liver to 4-trans-hydroxyglyburide and 3-cis-hydroxyglyburide; 50% of these compounds is excreted in the urine and 50% in the bile. Although the serum concentration of glyburide can be measured by radioimmunoassay and high-performance liquid chromatography, the importance of its serum concentration in the reduction of hyperglycemia is not yet established. Glyburide has a therapeutic effectiveness comparable to that of the first-generation sulfonylurea chlorpropamide; however, it has a lower frequency of adverse effects. To date it has a low frequency of clinically significant interactions with other drugs. Glyburide should not be prescribed for patients with liver disease or significant renal disease. Because glyburide is a potent hypoglycemic agent, it should be prescribed in small initial doses, particularly for elderly patients with diabetes. At the present time there is no definite evidence that it modifies the increased risk of cardiovascular disease of diabetic patients. Although glyburide is a potent stimulator of pancreatic insulin secretion after short-term administration, an additional mechanism of action during long-term administration is to decrease the resistance of muscle and liver to the action of insulin. It is a useful medication for patients with type II diabetes whose hyperglycemia is not adequately reduced by dietary management and exercise. It can be used as the initial drug in these patients or as the replacement drug for those with primary or secondary failure during therapy with first-generation sulfonylureas.

Pharmacokinetics and metabolic effects of glibenclamide and glipizide in type 2 diabetics

Fifteen Type 2 diabetics were treated for 4-week periods with once daily (10 mg) glibenclamide, glipizide and placebo according to a double-blind cross-over protocol. Post-dose glipizide concentrations were three times higher than those of glibenclamide, due to the incomplete bioavailability of the latter. On the other hand, pre-dose drug levels were similar, as an expression of the slower absorption and/or elimination of glibenclamide. Both active treatments reduced postprandial blood glucose concentrations and 24-hour urinary glucose excretion to a similar degree, but fasting blood glucose concentrations were slightly lower during glibenclamide treatment. Both active treatments enhanced fasting and postprandial insulin and C-peptide concentrations, the C-peptide response being greater after glipizide than after glibenclamide. Plasma glucagon and GIP concentrations were not significantly affected. Insulin sensitivity was increased by glibenclamide but not by glipizide. Neither therapy affected insulin binding to erythrocytes. It appears that both glibenclamide and glipizide improved glucose metabolism by sustained stimulation of insulin secretion, which was most pronounced with glipizide. Only glibenclamide improved insulin sensitivity and was slightly more active than glipizide on fasting blood glucose levels. The differences may be consequences of the pharmacokinetics, but differences in pharmacodynamics cannot be excluded.

Clinical pharmacology of glipizide

The clinical pharmacology of glipizide and other sulfonylureas is briefly reviewed. Reevaluation of the University Group Diabetes Program data suggests that sulfonylureas do not increase cardiovascular mortality. Instead, a long-term study of subjects with impaired glucose tolerance indicates that sulfonylureas reduce the frequency of cardiovascular morbidity and can postpone or even prevent the development of impaired glucose tolerance to manifest diabetes. It is likely that all sulfonylureas have the same principal mechanism(s) of action but that they differ in potency and pharmacokinetics, resulting in considerable clinical differences. Thus, glipizide and glibenclamide (glyburide) are much more potent than tolbutamide and chlorpropamide. Glipizide has the most rapid absorption and onset of action, as well as the shortest half-life and effect-duration; hence the risk of long-lasting hypoglycemia is minute. Glipizide has complete bioavailability, and its blood glucose-lowering effect is improved when it is given before breakfast. Glipizide may be administered once daily without loss of therapeutic efficacy.