Clinical pharmacology of sulphonylurea hypoglycaemic agents: part 2

Antidiabetic therapies and male reproductive function: where do we stand?

Diabetes mellitus has been increasing at alarming rates in recent years, thus jeopardizing human health worldwide. Several antidiabetic drugs have been introduced in the market to manage glycemic levels, and proven effective in avoiding, minimizing or preventing the appearance or development of diabetes mellitus-related complications. However, and despite the established association between such pathology and male reproductive dysfunction, the influence of these therapeutic interventions on such topics have been scarcely explored. Importantly, this pathology may contribute toward the global decline in male fertility, giving the increasing preponderance of diabetes mellitus in young men at their reproductive age. Therefore, it is mandatory that the reproductive health of diabetic individuals is maintained during the antidiabetic treatment. With this in mind, we have gathered the available information and made a critical analysis regarding the effects of several antidiabetic drugs on male reproductive function. Unlike insulin, which has a clear and fundamental role on male reproductive function, the other antidiabetic therapies' effects at this level seem incoherent. In fact, studies are highly controversial possibly due to the different experimental study approaches, which, in our opinion, suggests caution when it comes to prescribing such drugs to young diabetic patients. Overall, much is still to be determined and further studies are needed to clarify the safety of these antidiabetic strategies on male reproductive system. Aspects such as the effects of insulin levels variations, consequent of insulin therapy, as well as what will be the impact of the side effect hypoglycemia, common to several therapeutic strategies discussed, on the male reproductive system are still to be addressed.

ABCC9/SUR2 in the brain: Implications for hippocampal sclerosis of aging and a potential therapeutic target

The ABCC9 gene and its polypeptide product, SUR2, are increasingly implicated in human neurologic disease, including prevalent diseases of the aged brain. SUR2 proteins are a component of the ATP-sensitive potassium ("KATP") channel, a metabolic sensor for stress and/or hypoxia that has been shown to change in aging. The KATP channel also helps regulate the neurovascular unit. Most brain cell types express SUR2, including neurons, astrocytes, oligodendrocytes, microglia, vascular smooth muscle, pericytes, and endothelial cells. Thus it is not surprising that ABCC9 gene variants are associated with risk for human brain diseases. For example, Cantu syndrome is a result of ABCC9 mutations; we discuss neurologic manifestations of this genetic syndrome. More common brain disorders linked to ABCC9 gene variants include hippocampal sclerosis of aging (HS-Aging), sleep disorders, and depression. HS-Aging is a prevalent neurological disease with pathologic features of both neurodegenerative (aberrant TDP-43) and cerebrovascular (arteriolosclerosis) disease. As to potential therapeutic intervention, the human pharmacopeia features both SUR2 agonists and antagonists, so ABCC9/SUR2 may provide a "druggable target", relevant perhaps to both HS-Aging and Alzheimer's disease. We conclude that more work is required to better understand the roles of ABCC9/SUR2 in the human brain during health and disease conditions.

Sulfonylureas: a new look at old therapy

Sulfonylurea compounds were the first available oral antidiabetic agents and they remain an important tool in our quest for optimal glucose control. The sulfonylureas stimulate the release of insulin from pancreatic β-cells and have a number of extrapancreatic effects, including decreasing hepatic insulin clearance and reducing glucagon secretion in patients with type 2 diabetes. Although these agents have been the mainstay of pharmacotherapy for patients with type 2 diabetes mellitus (T2DM), their safety and clinical utility has been a matter of active debate in recent years, as their use is associated with risks of hypoglycemia and weight gain. We review the discovery and mechanisms of action of sulfonylureas, and the results of clinical trials to provide practical information on the pros and cons of their use in clinical practice. This review addresses advances in our understanding of mechanisms of action of sulfonylurea agents, their efficacy in T2DM, side effects, and impact on cardiovascular disease outcomes.

A novel l-isoleucine hydroxylating enzyme, l-isoleucine dioxygenase from Bacillus thuringiensis, produces (2S,3R,4S)-4-hydroxyisoleucine

The unique function of 4-hydroxyisoleucine (4-HIL) is to stimulate glucose-induced insulin secretion in a glucose-dependent manner. 4-HIL is distributed only in certain kinds of plants and mushrooms, but the biosynthetic mechanism of 4-HIL has not been elucidated. Moreover, 4-HIL-producing microorganisms have not been reported. l-isoleucine (l-Ile) hydroxylating activity producing 4-HIL was detected in a cell lysate of Bacillus thuringiensis strain 2e2 AKU 0251 obtained from the mid-late exponential phase of growth. Properties of the purified hydroxylase demonstrated that it is a alpha-ketoglutaric acid (alpha-KG) dependent l-Ile dioxygenase (IDO) and requires alpha-KG, ferric ion, and ascorbic acid for its maximum activity. IDO showed high stereoselectivity in l-Ile hydroxylation producing only (2S,3R,4S)-4-HIL. The N-terminal 22 amino acids sequence revealed high homology to a hypothetical protein (GenBank ID: RBTH_06809) in B. thuringiensis serovar israelensis ATCC 35646. The histidine motif, which is conserved in alpha-KG dependent dioxygenases, is found in RBTH_06809.

Drug-Induced Endocrine and Metabolic Disorders

Complex interactions exist amongst the various components of the neuroendocrine system in order to maintain homeostasis, energy balance and reproductive function. These components include the hypothalamus-pituitary- adrenal and -gonadal axes, the renin-angiotensin-aldosterone system, the sympathetic nervous system and the pancreatic islets. These hormones, peptides and neurotransmitters act in concert to regulate the functions of many organs, notably the liver, muscles, kidneys, thyroid, bone, adrenal glands, adipocytes, vasculature, intestinal tract and gonads, through many intermediary pathways. Endocrine and metabolic disorders can arise from imbalance amongst numerous hormonal factors. These disturbances may be due to endogenous processes, such as increased secretion of hormones from a tumour, as well as exogenous drug administration. Drugs can cause endocrine abnormalities via different mechanisms, including direct alteration of hormone production, changes in the regulation of the hormonal axis, effects on hormonal transport, binding, and signalling, as well as similar changes to counter-regulatory hormone systems. Furthermore, drugs can affect the evaluation of endocrine parameters by causing interference with diagnostic tests. Common drug-induced endocrine and metabolic disorders include disorders of carbohydrate metabolism, electrolyte and calcium abnormalities, as well as drug-induced thyroid and gonadal disorders. An understanding of the proposed mechanisms of these drug effects and their evaluation and differential diagnosis may allow for more critical interpretation of the clinical observations associated with such disorders, better prediction of drug-induced adverse effects and better choices of and rationales for treatment.

Cytochrom-P450 mediierte Arzneimittelinteraktionen mit Antibiotika

This review focuses on drug interactions with commonly prescribed antibiotics. With each drug coadministered, the likelihood of an adverse interaction increases exponentially. Thus, poly-pharmacotherapy possesses important clinical challenges for clinicians and exposes patients to potentially life-threatening risks. In particular, following co-administration of drugs such as tricyclic antidepressants, anticoagulants and antiarrhythmics, which are characterized by narrow therapeutic windows, even small changes in plasma levels can cause serious adverse reactions and/or therapeutic failure. The hepatic and intestinal cytochrome, or CYP-450 enzyme system is responsible for the biotransformation of a multitude of drugs and is frequently involved in drug interactions. The present review therefore presents a comprehensive overview on potential drug interactions with antibiotics, which are mediated by the cytochrome-P450-enzymes.

Effects of Chinese Herbal Medicines on Intestinal Drug Absorption

Sho-saiko-to (Xiao-Chai-Hu-Tang), one of the major traditional Chinese medicines, has been frequently prescribed with other synthetic or biotechnological drugs for the treatment of various acute or chronic diseases in Japan, and thus it is important to understand the interactions between Sho-saiko-to and coadministered drugs. This paper reviews the effects of Sho-saiko-to on the pharmacokinetics and pharmacodynamics of concomitant drugs in the gastrointestinal tract. Sho-saiko-to slightly hastens the gastrointestinal absorption of the sulfonylurea compound tolbutamide. Furthermore, it is considered that the increase in the gastrointestinal absorption rate by Sho-saiko-to may potentiate the hypoglycemic effects of tolbutamide in the early period after oral administration. Sho-saiko-to can facilitate the epithelial membrane permeability of tolbutamide at an early phase across the rat jejunum in situ and Caco-2 cell monolayers. It is also suggested that Sho-saiko-to enhances the energy-dependent transport of tolbutamide and has an inhibitory effect on the passive paracellular transport of tolbutamide in Caco-2 cells. This result might be related to the accelerated in vivo absorption rate of tolbutamide by concomitant dosing with Sho-saiko-to in rats. In addition, Sho-saiko-to has inhibitory effects on the efflux pump mediated by MDR1, and it appears that the crude constituents in Glycyrrhizae radix, glycyrrhizic acid and liquiritin, contribute to MDR1 suppression.

Use of insulin and oral hypoglycemic medications in patients with diabetes mellitus and advanced kidney disease

Diabetes mellitus is recognized as a leading cause of chronic kidney disease (CKD) and end-stage renal disease (ESRD) in the United States. There is a vast array of medications used to treat diabetes, including insulin and the sulfonylureas, as well as newer classes of drugs such as the thiazolidinediones and biguanides. In patients with reduced glomerular filtration rate (GFR), it is necessary to decrease the dosage of some of these drugs, while others are best avoided altogether. Accumulation of either the parent compound or its metabolites can result in symptomatic hypoglycemia, or in the case of metformin, significant lactic acidosis. In this article we will review the use of insulin and the various classes of oral medications used to treat type 2 diabetes mellitus, focusing on their pharmacokinetic properties and dosing in patients with advanced kidney disease.

Transepithelial Permeation of Tolbutamide across the Human Intestinal Cell Line, Caco-2

Sulfonylurea hypoglycemic agents have interindividual variability in the gastrointestinal absorption rate. However, the absorption mechanism at the intestinal epithelium has not yet been clarified. To elucidate contribution of the specific mechanism for transepithelial transport of sulfonylureas, the apical-to-basolateral and basolateral-to-apical transport studies of tolbutamide were carried out using Caco-2 cell monolayers cultured on the polycarbonate membrane. The transported amounts of the substrate were measured by HPLC to estimate the apparent permeability coefficients (P(app)). In the apical-to-basolateral flux, the transport activity of tolbutamide was facilitated when the pH of the apical medium was more acidic than the basolateral one. ATP-depletion decreased the P(app) of tolbutamide. The kinetic analysis of the permeation rate indicated that the saturable process largely contributed to the tolbutamide flux. The P(app) of tolbutamide was lowered by an ionophore and monocarboxylic acids, while dicarboxylic acids and the inhibitor for the anion exchanger had no effect. In addition, mutual inhibition with benzoic acid was observed in transepithelial transport of tolbutamide. On the other hand, the permeation rate of tolbutamide from the basolateral to apical side was concentration-independent and neither affected by metabolic inhibitors, probenecid nor inhibitors for P-glycoprotein. In conclusion, these results suggest that apical-to-basolateral transport of tolbutamide across the Caco-2 cell monolayers is mediated by the pH-dependent specific system, presumably shared with other organic anions such as benzoic acid.

Oral agents for the treatment of type 2 diabetes mellitus: pharmacology, toxicity, and treatment

Currently available oral agents for the treatment of type 2 diabetes mellitus include a variety of compounds from 5 different pharmacologic classes with differing mechanisms of action, adverse effect profiles, and toxicities. The oral antidiabetic drugs can be classified as either hypoglycemic agents (sulfonylureas and benzoic acid derivatives) or antihyperglycemic agents (biguanides, alpha-glucosidase inhibitors, and thiazolidinediones). In this review, a brief discussion of the pharmacology of these agents is followed by an examination of the adverse effects, drug-drug interactions, and toxicities. Finally, treatment of sulfonylurea-induced hypoglycemia is described, including general supportive care and the management of pediatric sulfonylurea ingestions. The adjunctive roles of glucagon, diazoxide, and octreotide for refractory hypoglycemia are also discussed.

Comparison of Capillary Electrophoresis with HPLC for Diagnosis of Factitious Hypoglycemia

Background: The diagnosis of “factitious hypoglycemia” is essentially based on the disclosure of hypoglycemic agents in blood or urine. The aim of this study was to evaluate the performance of capillary electrophoresis (CE) as a quantitative method for determination of chlorpropamide, tolbutamide, glipizide, gliclazide, and glibenclamide in serum.

Methods: Serum samples (1 mL), with internal standard added, were purified by solid-phase extraction on OASISTM HLB cartridges (Waters), dried under reduced pressure, and reconstituted with 30–60 μL of acetonitrile:H2O. Analysis was carried out by micellar electrokinetic capillary chromatography in 5 mmol/L borate, 5 mmol/L phosphate, 75 mmol/L sodium cholate, pH 8.5, containing 25 mL/L methanol. Separation was accomplished in a 20 cm × 50 μm (i.d.) silica capillary at 25 °C and a constant voltage of +10 kV. Pharmacokinetics of gliclazide (80-mg tablet) in a diabetic patient were assayed by both HPLC and CE. Two hypoglycemic patients positive by HPLC analysis for unreported gliclazide and tolbutamide overdose were also screened by CE.

Results: Separation of six drugs (including the internal standard) was accomplished in 5 min plus 5 min rinsing. The between-day CV of the ratio of the areas of the sulfonylurea drugs to internal standard was <1% (n = 10). Linearity (r2 ≥0.998) and recovery (≥80%) were good for all sulfonylurea drugs tested. Pharmacokinetic curves for gliclazide by CE and HPLC were superimposable. CE analysis confirmed the HPLC diagnosis of surreptitious abuse of gliclazide and tolbutamide.

Conclusion: CE is a useful tool in the clinical chemistry and toxicology laboratory for drug monitoring and pharmacokinetic investigations.

Comparative tolerability of sulphonylureas in diabetes mellitus

The sulphonylurea drugs have been the mainstay of oral treatment for patients with diabetes mellitus since they were introduced. In general, they are well tolerated, with a low incidence of adverse effects, although there are some differences between the drugs in the incidence of hypoglycaemia. Over the years, the drugs causing the most problems with hypoglycaemia have been chlorpropamide and glibenclamide (glyburide), although this is a potential problem with all sulphonylureas because of their action on the pancreatic beta cell, stimulating insulin release. Other specific problems have been reported with chlorpropamide that occur only rarely, if at all, with other sulphonylureas. Hyponatraemia secondary to inappropriate antidiuretic hormone activity, and increased flushing following the ingestion of alcohol, have been well described. The progressive beta cell failure with time results in eventual loss of efficacy, as these agents depend on a functioning beta cell and are ineffective in the absence of insulin-producing capacity. Differences in this secondary failure rate have been reported, with chlorpropamide and gliclazide having lower failure rates than glibenclamide or glipizide. The reasons for this are unclear, but the more abnormal pattern of insulin release produced by glibenclamide may be partly responsible and, indeed, may explain the increased risk of hypoglycaemia with this agent. Previously reported increased mortality associated with tolbutamide therapy has not been substantiated, and more recent data have shown no increased mortality from sulphonylurea treatment. Indeed, benefit from glycaemic control, regardless of the agent used--insulin or sulphonylurea--was reported by the United Kingdom Prospective Diabetes Study. Nevertheless, there is still ongoing controversy in view of the experimental evidence, mainly from animal studies, of potential adverse effects on the heart from sulphonylureas, but these are difficult to extrapolate into clinical situations. Most of these studies have been carried out with glibenclamide, which makes comparison of possible risk difficult. Other cardiovascular risk factors may be modified by gliclazide, which seems unique among the sulphonylureas in this respect. Its reported haemobiological and free radical scavenging activity probably resides in the azabicyclo-octyl ring structure in the side chain. Reduced progression or improvement in retinopathy has been reported in comparative trials with other sulphonylureas, and the effect is unrelated to improvements in glycaemia. There are differences between the sulphonylureas in some adverse effects, risk of hypoglycaemia, failure rates and actions on vascular risk factors. As a group of drugs, they are very well tolerated, but differences in overall tolerability can be identified.

A Chinese traditional medicine, sho-saiko-to (xiao-chaihu-tang), reduces the bioavailability of tolbutamide after oral administration in rats

The effects of Sho-saiko-to on the pharmacokinetics of tolbutamide were investigated in rats. After intravenous administration of tolbutamide (5 mg/kg), no significant change in the pharmacokinetics of tolbutamide was observed in both groups of single and multiple (7 days) pre-administration of Sho-saiko-to (500 mg/kg). In the study of single oral administration of tolbutamide (50 mg/kg), co-administration of Sho-saiko-to tended to accelerate the initial absorption rate of tolbutamide. The area under the plasma concentration-time curve of tolbutamide after oral administration was significantly reduced by Sho-saiko-to. Subsequently, a significant decrease was observed in the oral bioavailability of this drug when Sho-saiko-to was given concomitantly. These findings suggest that Sho-saiko-to reduces the bioavailability of tolbutamide after oral administration in rats, and that this change is not related to hepatic metabolism.

Population-based modeling to demonstrate extrapancreatic effects of tolbutamide

Tolbutamide is used increasingly as an investigative tool in in vivo studies of the physiology of glucose tolerance. Its hypoglycemic effect in nondiabetic subjects is widely variable, reflecting possible variability in its pharmacokinetics, an insulinergic response, an extrapancreatic effect of the drug, or the hypoglycemic effect of insulin itself. Using population-based modeling, we have investigated the kinetics and dynamics of tolbutamide and assessed covariates in two groups of healthy subjects. The results indicate a high variability in insulinergic effect, measured by the area under of the curve of insulin (0-60 min), in response to tolbutamide injection (coefficient of variation = 29-96%). However, it appears that impaired insulin sensitivity is compensated by higher insulin secretion in response to tolbutamide. Thus the hypoglycemic effect of high insulin secretion is minimal in insulin-resistant subjects. Application of the model indicated that tolbutamide has appreciable extrapancreatic effects mediated by prolongation of the residence time of insulin in a remote effect and by enhancement of glucose effectiveness. An effect in increasing the insulin sensitivity index is also possible but could not be confirmed statistically for all groups of subjects studied. These observations may explain inconsistencies between the results of tolbutamide and insulin injection in the frequently sampled intravenous glucose tolerance test and call for further study of insulin- vs. tolbutamide-modified frequently sampled intravenous glucose tolerance tests in the assessment of the insulin sensitivity and glucose effectiveness indexes.

Effects of Sho-saiko-to on the pharmacokinetics and pharmacodynamics of tolbutamide in rats

Although Sho-saiko-to (Xiao Chai Hu Tang), a major Chinese traditional medicine, is frequently prescribed with other synthetic or biotechnological drugs for the treatment of various chronic diseases, there is a dearth of information about interactions between sho-saiko-to and co-administered drugs. This paper reports the effects of Sho-saiko-to on the pharmacokinetics and glucose responses of a sulphonylurea hypoglycaemic agent, tolbutamide, after their oral administration in rats. After oral administration of tolbutamide (50 mg kg(-1)) with or without Sho-saiko-to extract powder (300 mg kg(-1)) to male Sprague-Dawley rats cannulated in the jugular vein, plasma tolbutamide and glucose levels were periodically measured. Co-administration of Sho-saiko-to tended to elevate the plasma tolbutamide concentration in the absorption phase. A two-compartment lag-time model was found to describe the plasma tolbutamide concentration-time data. The maximum concentration of tolbutamide was significantly increased and time to reach the maximum concentration was reduced to about 70% by co-administration with Sho-saiko-to. There was no significant change in area under the curve or in the elimination half-life of tolbutamide. The extent of the lowering effect of tolbutamide on plasma glucose levels was increased up to 0.75 h and decreased after 5 h after co-administration of Sho-saiko-to. In conclusion, these studies suggest that sho-saiko-to slightly hastens the gastrointestinal absorption of tolbutamide. Furthermore, it is considered that elevation of the gastrointestinal absorption rate by Sho-saiko-to might potentiate the hypoglycaemic effect of this sulphonylurea in the early period after oral administration.

Rates of hypoglycemia in users of sulfonylureas

OBJECTIVE

To identify the demographic and clinical characteristics of sulfonylurea users. To assess the risk of hypoglycemia in patients treated with sulfonylureas in clinical practice, and to characterize the risk in relation to the different drugs used.

RESEARCH DESIGN AND METHODS

A cohort of 33,243 sulfonylurea users chosen from 719 clinical practices in the United Kingdom were identified through the VAMP-Research database. Information on demographic characteristics, medical diagnoses and use of medical services was obtained through the computerized records. For a stratified sample of 500 patients, general practioners completed a structured questionnaire on the duration, treatment, and complications of diabetes mellitus, obesity, alcohol use, and smoking history. Patients with a diagnosis of hypoglycemia, as recorded in the database within a time-window of a sulfonylurea prescription, were identified. Incidence rates per person-year of sulfonylurea therapy were estimated.

RESULTS

Other than a longer duration of diabetes in users of chlorpropamide, no differences were observed among users of different sulfonylurea agents with respect to diabetic complications, adequacy of diabetic control, obesity, smoking, and excessive alcohol consumption. A diagnosis of hypoglycemia during sulfonylurea therapy was recorded in 605 people over 34,052 person-years of sulfonylurea therapy, which converted into an annual risk of 1.8%. The risk in glibenclamide users was higher than in users of other types of sulfonylureas uses. Duration of therapy, concomitant use of insulin, sulfonylurea-potentiating or antagonizing and concomitant use of beta-blockers were predictive of the risk of developing hypoglycemia.

DISCUSSION

Drug use patterns showed comparability among users of different sulfonylurea agents. Our findings suggest that the rate of diagnosis of hypoglycemia made by physicians is higher for glibenclamide than for other sulfonylureas. An epidemiological study with objectively diagnosed hypoglycemia should be undertaken to confirm these results.

Oral antidiabetic drug use in the elderly

Non-insulin-dependent diabetes mellitus (NIDDM) is a metabolic disease that is common in the elderly, and is characterised by insulin insufficiency and resistance. Measures such as bodyweight reduction and exercise improve the metabolic defects, but pharmacological therapy is the most frequently used and successful therapy. The sulphonylureas stimulate insulin secretion. Metformin and troglitazone increase glucose disposal and decrease hepatic glucose output without causing hypoglycaemia. Acarbose is a dietary aid that spreads the dietary carbohydrate challenge to endogenous insulin over time. These pharmacological agents, either alone or in combination, should improve blood glucose regulation in patients with NIDDM.

A rapid- and short-acting hypoglycemic agent KAD-1229 improves post-prandial hyperglycemia and diabetic complications in streptozotocin-induced non-insulin-dependent diabetes mellitus rats

We investigated therapeutic effects of a rapid- and short-acting non-sulfonylurea hypoglycemic agent, calcium (2S)-2-benzyl-3-(cis-hexahydro-2-isoindolinylcarbonyl)propionate dihydrate (KAD-1229), on streptozotocin (STZ)-induced non-insulin-dependent diabetes mellitus (NIDDM) rats. The effects exerted by KAD-1229 on the post-prandial plasma glucose rise in STZ-induced mild NIDDM (mNIDDM) rats were different from those of sulfonylureas. When KAD-1229 with liquid meal (10 kcal/kg) was given to the mNIDDM rats, the plasma glucose migration was similar to that of normal healthy rats. On the contrary, glibenclamide had little or no effect on the plasma glucose rise 0.5-1 hr after oral administration, and its effect was only evident 2-5 hr after dosing. Tolbutamide showed similar hypoglycemia to that induced by glibenclamide at 2-5 hr with insufficient efficacy at 0.5 hr. Gliclazide sufficiently suppressed the level of post-prandial plasma glucose. However, its complete inhibition of post-prandial plasma glucose was associated with the extra-hypoglycemia 1-5 hr after oral administration. We also tested the efficacy of KAD-1229 in more severe STZ-induced NIDDM (sNIDDM) rats to elucidate the effects of the drug on the long-term glycemic controls and diabetic complications. When the sNIDDM rats were treated with 10 mg/kg KAD-1229 twice a day for about 17 weeks, increases in fasting plasma glucose and hemoglobin A1c were inhibited. Furthermore, treatment with KAD-1229 suppressed the development of microalbuminuria and cortical cataract. We conclude that the rapid- and short-acting insulinotropic agent KAD-1229 is able to improve the deterioration in the glycemic controls and inhibit the development of diabetic complications in STZ-induced NIDDM rats.

Chlorpropamide-induced cholestatic liver failure resulting in death

OBJECTIVE

To describe the first reported case of a death that occurred as a result of chlorpropamide-induced cholestatic liver disease.

METHODS

We review the clinical and laboratory details of an 81-year-old man with type II diabetes mellitus, who was hospitalized because of nausea, vomiting, and jaundice.

RESULTS

The patient had been taking a sulfonylurea (chlorpropamide, 250 mg orally three times a day) for 2 months. On initial assessment, the patient was noted to have cutaneous and scleral icterus and an erythematous maculopapular rash on the torso. The alkaline phosphatase level was substantially increased, and the transaminases were mildly increased. Use of all medications was discontinued. In the hospital, the patient's status rapidly deteriorated, and death ensued after cardiopulmonary arrest on day 6.

CONCLUSION

The findings were consistent with a hypersensitivity reaction to chlorpropamide that ultimately resulted in fulminant cholestatic liver disease and death.

Effects of aspirin and ibuprofen on the pharmacokinetics and pharmacodynamics of glyburide in healthy subjects

OBJECTIVE

To determine the effects of aspirin and ibuprofen on the pharmacokinetics and pharmacodynamics of glyburide in healthy volunteers.

DESIGN

Single-center, randomized, two-way, crossover design following an initial baseline evaluation phase.

SETTING

Outpatient, university-based ambulatory care facility.

PATIENTS

Sixteen healthy nonsmoking men aged 20-34 years.

INTERVENTION

Three phases consisting of six treatments. Phase 1 began with treatment A, a baseline oral glucose tolerance test (GTT), followed by treatment B, glyburide 5 mg plus a GTT. The other two phases were administered in a crossover design. Phase 2 consisted of the administration of aspirin 975 mg qid for 4 days. On day 3 a GTT was administered (treatment C) and on day 4 glyburide 5 mg plus a GTT was administered (treatment E). Phase 3 consisted of the administration of ibuprofen 600 mg qid for 4 days with a GTT on day 3 (treatment D) and glyburide 5 mg plus a GTT on day 4 (treatment F).

MAIN OUTCOME MEASURES

Serum glyburide concentrations after each treatment, as well as glucose and insulin, ibuprofen, and salicylate serum concentrations and glyburide free fractions.

RESULTS

Aspirin administration resulted in an 85% increase in mean total glyburide oral clearance and a 29% increase in glyburide free fraction. Ibuprofen administration resulted in a slight increase in mean glyburide free fraction, but no significant changes in glyburide pharmacokinetic parameters were observed. Insulin concentrations were increased during the glyburide plus aspirin treatment. Conflicting results were observed in the glucose parameters.

CONCLUSIONS

The potential for this glyburide-aspirin interaction resulting in a transient hypoglycemia should be considered in diabetic patients receiving glyburide therapy.

Glibenclamide vs gliclazide in type 2 diabetes of the elderly

The objective of this study was to compare the effect of two sulphonylureas on the frequency of hypoglycaemic events and glycaemic control in elderly patients with Type 2 diabetes. Twenty-two untreated elderly patients were treated with glibenclamide or gliclazide in a randomized double-blind fashion. Prior to treatment, a biochemical profile, an oral glucose tolerance test, and a 2-h hyperglycaemic glucose clamp (glucose 5.4 mmol l-zs-1 above baseline) were performed. Patients were seen regularly over 6 months to assess glycaemic control and the frequency of hypoglycaemic reactions. Hyperglycaemic clamp studies and oral glucose tolerance tests were repeated at 1 and 6 months. The area under the curve for the oral glucose tolerance test (glibenclamide: 15.5 +/- 0.7; gliclazide: 14.9 +/- 0.8 mmol l-1 (p = NS)) and the haemoglobin A1C (glibenclamide: 7.4 +/- 0.2%; gliclazide: 7.9 +/- 0.5% (p = NS)) were similar at 6 months. Hypoglycaemic reactions were significantly more frequent with glibenclamide than with gliclazide: 17 vs 4 (p < 0.01). Insulin sensitivity index (ml kg-1 min-1 pmol-1 x 100) was increased significantly by glibenclamide but not gliclazide (glibenclamide: 0.284 +/- 0.116 (baseline) vs 0.518 +/- 0.102 (6 months) (p < 0.05), gliclazide: 0.260 +/- 0.048 (baseline) vs 0.358 +/- 0.048 (6 months) (p = NS)). We conclude that glycaemic control was equivalent with the two drugs but the incidence of hypoglycaemic reactions was significantly greater with glibenclamide probably because this drug increases insulin sensitivity to a greater degree.

Problems and pitfalls of sulphonylurea therapy in older patients

The prevalence of non-insulin-dependent diabetes mellitus (type II) increases with age, so that approximately half of all known patients in English-speaking countries are over 65 years of age. There is no reason to believe that the criteria for blood glucose control should be any less stringent for elderly patients unless they have a limited life expectancy. Sulphonylurea drugs remain an effective means of achieving blood glucose control after failure of dietary therapy alone in older patients. However, changes in normal metabolism of drugs with age and the development of other pathologies in elderly patients make it important that these drugs are prescribed with care. Severe symptomatic hypoglycaemia is the most serious adverse effect of sulphonylurea drugs and this becomes progressively more likely with increasing age, depending primarily on the substantial reduction of renal function with normal aging. Other adverse effects are much less commonly of clinical importance. To minimise the risk of hypoglycaemia, it is important that patients receive closely supervised dietary management with education about their disease for at least 3 months before sulphonylurea drugs are prescribed. In elderly patients a short-acting agent with no active metabolites should be used. As patients become older, those receiving long-acting agents can be changed to short-acting agents before problems arise. If blood glucose control appears satisfactory on treatment, then symptoms of hypoglycaemia should be sought. If control is poor, then the criteria for introduction of insulin, with appropriate education, do not differ from those in younger patients.

Determination of glibenclamide and its two major metabolites in human serum and urine by column liquid chromatography

A simple reversed-phase liquid chromatographic method for the measurement of low concentrations of glibenclamide (glyburide) and its two major metabolites, 4-trans- and 3-cis-hydroxyglibenclamide, in human serum and urine has been developed. The compounds were extracted with n-hexane-dichloromethane (1:1). The UV detection wavelength was 203 nm. The minimum detectable serum level of glibenclamide was 1 ng ml (2 nM), and the relative standard deviation was 8.9% (n = 9). When maximum sensitivity was desired the metabolites were chromatographed separately. Metabolites in urine were measured by the same method after five-fold sample dilution. The utility of the method was tested on a healthy volunteer who ingested 3.5 mg of glibenclamide. The parent drug was present in the serum for at least 18 h, and the metabolites in the urine for at least 24 h.

Chlorpropamide overdose in renal failure: management with charcoal hemoperfusion

A potentially lethal chlorpropamide overdose in a patient with chronic renal failure on long-term hemodialysis was treated by two courses of charcoal hemoperfusion. Hemoperfusion shortened the half-life clearance of the drug from a mean value of 93.6 to 3.4 hours. Calculation of the fractional extraction indicated that hemoperfusion reduced the body burden of the drug by 24% and 19% (mean values) during the first and second hours of treatment, respectively. We conclude that charcoal hemoperfusion should be considered a definitive therapeutic option in such cases.

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.

Lack of primary effect of sulphonylurea (glipizide) on plasma lipoproteins and insulin action in former type 2 diabetics with attenuated insulin secretion

A double-blind, placebo-controlled investigation has been made into the effects of 8 weeks of glipizide treatment in diabetics previously classified as Type 2 but with subsequent attenuation of insulin secretion and thence maintained on exogenous insulin. Although all patients were exposed to therapeutic plasma concentrations of glipizide, fasting blood glucose, haemoglobin A1 and plasma lipoproteins (HDL, LDL, total cholesterol and triglycerides) did not show any consistent improvement following this treatment. It appears unlikely that SU (glipizide) has any primary effect on insulin action or on plasma lipoproteins. Its primary action is to augment insulin release and availability, so, its use should be restricted to Type 2 diabetics who retain insulin secretion.

Serum gliclazide concentration in diabetic patients. Relationship between gliclazide dose and serum concentration

Serum levels of gliclazide were determined by radioimmunoassay in seven healthy controls and in 18 diabetic in-patients receiving single oral dosing and consecutive dosing over 5 days. Following a single oral dose of 40 mg in the seven controls and eight diabetic patients, and 120 mg in ten diabetic patients, the serum levels of gliclazide peaked on average at 2 h, followed by a slow decline, the t1/2 being 16.5 h in the volunteers, 12.3 h in the diabetic patients receiving 40 mg, and 10.5 h in those receiving 120 mg. During consecutive administration, the serum levels both at fasting and at the peak reached a plateau in 2 days and no further accumulations were observed. The steady-state peak levels of gliclazide in the diabetic patients revealed a strongly positive correlation with the dose per m2 body surface area (r = 0.78, P less than 0.001), and their steady-state fasting levels correlated positively but weakly with the dose per m2 body surface area (r = 0.48, P less than 0.05). Thus, measuring either the fasting or the peak concentration of gliclazide will be useful for monitoring drug concentration in the serum. Pharmacokinetics of gliclazide will contribute to the elucidation of the relationship of serum level and clinical effectiveness in diabetic subjects.

Anti-hyperglycaemic action of BRL 26830, a novel beta-adrenoceptor agonist, in mice and rats

BRL 26830, (R*,R*)-(+/-)-methyl 4-[2-[(2-hydroxy-2-phenylethyl)amino] propyl] benzoate, is a new orally active anti-hyperglycaemic agent. In 24 hr-fasted rats and mice, BRL 26830 decreased the blood glucose concentration following the administration of a subcutaneous glucose load. It also improved oral and intravenous glucose tolerance in 24 hr-fasted rats and decreased the post-prandial blood glucose concentration following the consumption of the complete, milk-based, meal "Nutrament". BRL 26830 produced a dose-related increase in the plasma insulin concentration and since it was inactive in lowering blood glucose in streptozotocin-diabetic rats, it is likely that its acute action on glucose tolerance was through the stimulation of insulin secretion. In contrast to the sulphonylurea, glibenclamide, BRL 26830 had no effect on the blood glucose concentration in 5 hr-fasted rats and only produced a transient reduction in 24 hr-fasted rats. BRL 26830 did not improve glucose tolerance when given acutely to hyperinsulinaemic C57BL/6 ob/ob mice. However, chronic treatment of these mice with BRL 26830 for 14-43 days resulted in a significant improvement in glucose tolerance.

Beta-blockers and glucose control

Literature on the effects of beta-blockers on blood glucose is reviewed. Data are presented regarding the adrenergic influences on glucose regulation and the effects of beta-blockade during hypo- and hyperglycemia in normal and diabetic individuals. beta-adrenergic stimulation enhances insulin and glucagon secretion, as well as glycogenolysis, gluconeogenesis, and lipolysis. alpha-adrenergic stimulation inhibits insulin secretion and may inhibit glucagon secretion and enhance liver glycogenolysis. In nondiabetics, beta-blockers represent minimal risk of affecting glucose control. In insulin-dependent diabetics, beta-blockers can prolong, enhance, or alter the symptoms of hypoglycemia, while hyperglycemia appears to be the major risk in noninsulin-dependent diabetics. beta-blockers can potentially increase blood glucose concentrations and antagonize the action of oral hypoglycemic drugs.

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.

Hypoglycemic coma induced by inadvertent administration of glyburide

A 79-year-old nondiabetic woman was inadvertently given a 5-mg tablet of glyburide. Blood glucose concentration was 2.6 mmol/L three hours after ingestion. The patient was discharged 9 hours after ingestion and readmitted 10 1/2 hours after ingestion, in a hypoglycemic coma (blood glucose, 0.65 mmol/L). She was treated with two bolus doses of dextrose and intravenous dextrose. Her blood glucose was abnormal until hospital day 3. On hospital day 4, she was discharged with no apparent sequelae. This patient's severe reaction may have been due to mild renal insufficiency or concurrent use of timolol. Should inadvertent administration of glyburide occur in a patient with impaired renal function, the patient should be monitored for at least 24 hours.

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.

Hypoglycemic activity of 1-alpha-(3,4-dimethoxyphenethylaminomethyl) -2-hydroxybenzylalcohol 1/2 fumarate (TA-078) in the mouse, rat and dog

1-alpha-(3,4-Dimethoxyphenethylaminomethyl)-2-hydroxybenzylalcohol 1/2 fumarate (TA-078) is a new hypoglycemic agent structurally different from any existing hypoglycemic drug. It depresses the rise of blood glucose when it is orally administered to glucose-loaded mice, rats and beagle dogs at minimal doses of 1, 10 and 2.5 mg/kg, respectively. In contrast with tolbutamide, TA-078 hardly affected fasting blood glucose levels in rats and dogs and only weakly reduced fasting blood glucose levels in mice. Oral administration of TA-078 to KK mice also improved glucose tolerance, while no improvement was observed in streptozotocin-diabetic rats. TA-078 elevated plasma immunoreactive insulin (IRI) levels in mice and rats soon after its oral administration. In fasted rats, TA-078 caused only a transient increase in plasma IRI but did not affect plasma immunoreactive glucagon (IRG) levels in the early phase after its administration. On the other hand, tolbutamide induced a sustained increase in plasma IRI and a transient but marked decrease in plasma IRG. In perfused rat pancreas, TA-078 stimulated insulin secretion. The stimulation by 10 micrograms/ml TA-078 in the perfusion liquid required the presence of a normal concn (5.6 mM) of glucose, whereas the same concn of tolbutamide stimulated insulin release even at a low glucose concn (2.8 mM).