Metformin and metoprolol CR treatment in non-obese men

Changes in Plasma Free Fatty Acids Associated with Type-2 Diabetes

Type 2 diabetes mellitus (T2DM) is associated with increased total plasma free fatty acid (FFA) concentrations and an elevated risk of cardiovascular disease. The exact mechanisms by which the plasma FFA profile of subjects with T2DM changes is unclear, but it is thought that dietary fats and changes to lipid metabolism are likely to contribute. Therefore, establishing the changes in concentrations of specific FFAs in an individual’s plasma is important. Each type of FFA has different effects on physiological processes, including the regulation of lipolysis and lipogenesis in adipose tissue, inflammation, endocrine signalling and the composition and properties of cellular membranes. Alterations in such processes due to altered plasma FFA concentrations/profiles can potentially result in the development of insulin resistance and coagulatory defects. Finally, fibrates and statins, lipid-regulating drugs prescribed to subjects with T2DM, are also thought to exert part of their beneficial effects by impacting on plasma FFA concentrations. Thus, it is also interesting to consider their effects on the concentration of FFAs in plasma. Collectively, we review how FFAs are altered in T2DM and explore the likely downstream physiological and pathological implications of such changes.

Effects of metformin on endothelial health and erectile dysfunction

Erectile dysfunction (ED) affects approximately 18 million American men. ED may be attributed to several etiologies, including arteriogenic, psychogenic, neurogenic, hormonal, drug-induced, and systemic disease or aging related factors. Specific to arteriogenic ED, three major mechanisms have been identified: (I) endothelium-dependent vasodilatory impairment; (II) sympathetic nerve activity elevation; (III) atherosclerotic luminal narrowing. Additionally, these insults have been linked to the insulin resistant state, which in turn is comorbid with obesity, dyslipidemia, diabetes, and hypertension. In this review, we summarize the evidence regarding the impact of metformin—an insulin sensitizer—on the three mechanisms of arteriogenic ED. We report that metformin treatment positively affects two of three pathways, specifically through enhanced endothelium-dependent vasodilation and sympathetic nerve activity attenuation, but does not seem to have a significant impact on hypertension regulation. Given the encouraging data found in both animal and clinical studies, we advocate for further studies on metformin use in ED.

Metformin treatment improves erectile function in an angiotensin II model of erectile dysfunction

INTRODUCTION

Increased angiotensin II (AngII) levels cause hypertension, which is a major risk factor for erectile dysfunction (ED). Studies have demonstrated that increased AngII levels in penile tissue are associated with ED. A recent study showed that metformin treatment restored nitric oxide synthase (NOS) protein expression in penile tissue in obese rats; however, whether metformin treatment can be beneficial and restore erectile function in a model of ED has not yet been established.

AIM

The goal of this study was to test the hypothesis that AngII induces ED by means of increased corpus cavernosum contraction, and that metformin treatment will reverse ED in AngII-treated rats.

METHODS

Male Sprague-Dawley rats were implanted with mini-osmotic pumps containing saline or AngII (70 ng/minute, 28 days). Animals were then treated with metformin or vehicle during the last week of AngII infusion.

MAIN OUTCOME MEASURES

Intracavernosal pressure; corpus cavernosum contraction and relaxation; nNOS protein expression; extracellular signal-regulated kinase (ERK1/2), AMP-activated protein kinase (AMPK), and eNOS protein expression and phosphorylation.

RESULTS

AngII-induced ED was accompanied with an increase in corpus cavernosum contractility, decreased nitrergic relaxation, and increased ERK1/2 phosphorylation. Metformin treatment improved erectile function in the AngII-treated rats by reversing the increased contraction and decreased relaxation. Metformin treatment also resulted in an increase in eNOS phosphorylation at ser1177.

CONCLUSIONS

Metformin treatment increased eNOS phosphorylation and improved erectile function in AngII hypertensive rats by reestablishing normal cavernosal smooth muscle tone.

Metformin: mechanisms of antihyperglycemic action, other pharmacodynamic properties, and safety perspectives

OBJECTIVE

To characterize the mechanisms of action of metformin and describe its effects and safety profile.

METHODS

Results of more than 30 years of clinical use in countries other than the United States are summarized. In addition, the pharmacologic properties of metformin are compared with those of other antihyperglycemic agents.

RESULTS

Approximately 90% of all cases of diabetes are non-insulin-dependent diabetes mellitus (NIDDM)--a heterogeneous disease that involves several pathogenic factors and is associated with other coexisting conditions, such as cardiovascular disease, hypertension, and obesity. Thus, an agent that controls blood glucose levels and has favorable effects on the concomitant conditions should be considered when pharmacologic intervention is needed for the treatment of NIDDM. Metformin possesses the pharmacodynamic properties to do both. Its mechanisms of action include the reduction of hepatic glucose production and enhancement of peripheral glucose disposal, making metformin an effective antihyperglycemic agent. It also has other pharmacologic properties, independent of its glycemic effects, that offer additional clinical benefits in comparison with other pharmacologic NIDDM treatments. These benefits include stabilization or even loss of weight in patients for whom weight gain is a concern and reduction of plasma lipid levels in patients with hyperlipidemia.

CONCLUSION

On the basis of 3 decades of clinical experience, metformin has been shown to be not only a well tolerated but also a highly effective antihyperglycemic agent.

Prevention and treatment of the metabolic syndrome

The prevalence of the metabolic syndrome is increasing owing to lifestyle changes leading to obesity. This syndrome is a complex association of several interrelated abnormalities that increase the risk for cardiovascular disease and progression to diabetes mellitus (DM). Insulin resistance is the key factor for the clustering of risk factors characterizing the metabolic syndrome. The National Cholesterol Education Program (NCEP) Adult Treatment Panel (ATP) III defined the criteria for the diagnosis of the metabolic syndrome and established the basic principles for its management. According to these guidelines, treatment involves the improvement of the underlying insulin resistance through lifestyle modification (eg, weight reduction and increased physical activity) and possibly by drugs. The coexistent risk factors (mainly dyslipidemia and hypertension) should also be addressed. Since the main goal of lipid-lowering treatment is to achieve the NCEP low-density lipoprotein cholesterol (LDL-C) target, statins are a good option. However, fibrates (as monotherapy or in combination with statins) are useful for the treatment of the metabolic syndrome that is commonly associated with hypertriglyceridemia and decreased high-density lipoprotein cholesterol (HDL-C) levels. The blood pressure target is < 140/90 mm Hg. The effect on carbohydrate homeostasis should possibly be taken into account in selecting an antihypertensive drug. Patients with the metabolic syndrome commonly have other less well-defined metabolic abnormalities (eg, hyperuricemia and raised C-reactive protein levels) that may also be associated with an increased cardiovascular risk. It seems appropriate to manage these abnormalities. Drugs that beneficially affect carbohydrate metabolism and delay or even prevent the onset of DM (eg, thiazolidinediones or acarbose) could be useful in patients with the metabolic syndrome. Furthermore, among the more speculative benefits of treatment are improved liver function in nonalcoholic fatty liver disease and a reduction in the risk of acute gout.

Insulin-lowering agents in the management of polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a medical condition that has brought multiple specialists together. Gynecologists, endocrinologists, cardiologists, pediatricians, and dermatologists are all concerned with PCOS patients and share research data and design clinical trials to learn more about the syndrome. Insulin resistance is a common feature of PCOS and is more marked in obese women, suggesting that PCOS and obesity have a synergistic effect on the magnitude of the insulin disorder. Hyperinsulinemia associated with insulin resistance has been causally linked to all features of the syndrome, such as hyperandrogenism, reproductive disorders, acne, hirsutism, and metabolic disturbances. Women with PCOS should be evaluated for cardiovascular risk factors, such as lipid profile and blood pressure. Modification of diet and lifestyle should be suggested to those who are obese. Several insulin-lowering agents have been tested in the management of PCOS. In particular, metformin is the only drug currently in widespread clinical use for treatment of PCOS. In a high percentage of patients, treatment with metformin is followed by regularization of menstrual cycle, reduction in hyperandrogenism and in cardiovascular risk factors, and improvement in response to therapies for induction of ovulation.

Do effects on blood pressure contribute to improved clinical outcomes with metformin?

Hyperinsulinaemia and hypertension commonly coexist, and a large body of evidence points to a common pathogenesis based on the presence of underlying insulin resistance (the "insulin hypothesis" of hypertension). Metformin improves insulin sensitivity in liver and muscle as its primary antihyperglycaemic mechanism of action, and intensive glycaemic management with metformin significantly reduced the risk of macrovascular diabetic complications in the UK Prospective Diabetes Study. The clinical outcome benefits in the metformin group included a significant reduction in the risk of stroke (- 41% vs + 14% with sulphonylurea or insulin treatment, p=0.032), which is well known to be highly sensitive to changes in blood pressure. Furthermore, a placebo-controlled study has shown that metformin significantly improved endothelial function, a key regulator of vascular tone and blood pressure, in type 2 diabetic patients. However, clinical studies have shown that metformin treatment is not associated with clinically relevant reductions in blood pressure in man. These apparently conflicting observations are difficult to reconcile. Either the beneficial vascular actions of metformin involve physiological systems not involved in the control of blood pressure, or counter-regulatory mechanisms prevent beneficial effects of metformin on the vasculature being translated into a clinically meaningful antihypertensive effect. Further research will be required to resolve this paradox.

Pathophysiology and pharmacological treatment of insulin resistance

Diabetes mellitus type 2 is a world-wide growing health problem affecting more than 150 million people at the beginning of the new millennium. It is believed that this number will double in the next 25 yr. The pathophysiological hallmarks of type 2 diabetes mellitus consist of insulin resistance, pancreatic beta-cell dysfunction, and increased endogenous glucose production. To reduce the marked increase of cardiovascular mortality of type 2 diabetic subjects, optimal treatment aims at normalization of body weight, glycemia, blood pressure, and lipidemia. This review focuses on the pathophysiology and molecular pathogenesis of insulin resistance and on the capability of antihyperglycemic pharmacological agents to treat insulin resistance, i.e., a-glucosidase inhibitors, biguanides, thiazolidinediones, sulfonylureas, and insulin. Finally, a rational treatment approach is proposed based on the dynamic pathophysiological abnormalities of this highly heterogeneous and progressive disease.

Combined metformin and insulin therapy for patients with type 2 diabetes mellitus

OBJECTIVE

This study was undertaken to assess the effects of combined treatment with insulin and metformin in patients with type 2 diabetes mellitus in whom dietary measures, weight control, and oral antihyperglycemic therapy had failed.

BACKGROUND

Insulin resistance in peripheral tissues, increased hepatic gluconeogenesis, and impaired insulin secretion are the underlying factors in the development of type 2 diabetes. Metformin is a biguanide antihyperglycemic agent that increases peripheral insulin sensitivity, reduces hepatic gluconeogenesis, and decreases intestinal glucose absorption.

METHODS

Thirty-one patients (24 women, 7 men; mean age, 61.8 years; mean body mass index [BMI], 28.0 kg/m2) were enrolled in this randomized, double-blind, 2-way, crossover, placebo-controlled study. Patients with type 2 diabetes who were treated previously with insulin or oral hypoglycemic agents and who had a glycosylated hemoglobin (HbA1c) level >9% or a fasting blood glucose level >8 mmol/L were included. Patients who were being treated with oral agents were switched to insulin therapy and required to maintain stable blood glucose control for 2 months prior to randomization. Patients received insulin plus either metformin 1,700 mg/d or placebo for 5 months, followed by a 2-month washout period, and were then crossed over to the other treatment arm for 5 months of additional treatment (total treatment period: 12 months).

RESULTS

Thirty patients completed the study; 1 patient withdrew early because of hypoglycemia. Compared with placebo, metformin produced significant reductions from overall baseline in mean daily insulin dose requirement (-8.69 units (17.2%], P < 0.001), HbA1c level (-0.74 [9.9%], P = 0.005), serum fructosamine level (-44.40 micromol/L, P = 0.026), 24-hour blood glucose profile (P = 0.008), and total cholesterol level (-0.42 mmol/L, P = 0.005). No treatment effects were observed on body weight, blood pressure, serum high-density lipoprotein cholesterol levels, or serum triglyceride levels. There was no correlation between BMI and reduction in HbA1C. No major side effects were reported.

CONCLUSIONS

Combination therapy with metformin and insulin improves glycemic control and reduces insulin requirements. with no major side effects, in patients with type 2 diabetes and may improve the risk profile in this patient population.

Metformin treatment leads to an increase in basal, but not insulin-stimulated, glucose disposal in obese patients with impaired glucose tolerance

AIMS

This study was initiated to test the hypothesis that metformin treatment leads to enhanced glucose disposal at ambient insulin concentrations.

METHODS

Nineteen obese patients with impaired glucose tolerance (IGT) were treated with either metformin or placebo in a randomized, double-blind, placebo-controlled, cross-over study. Insulin secretion and insulin resistance were quantified using the homeostasis model assessment (HOMA) and insulin-stimulated glucose disposal were measured by determining the steady-state plasma glucose (SSPG).

RESULTS

The average benefit of metformin was 0.6 mmol/l for glucose (95% confidence interval (CI) 0.2-0.9 P = 0.002), 2.8 pmol/l for insulin (95% CI 0.2-5.4, P = 0.019). Insulin resistance, as quantified by HOMA, was improved by 1.1 (95% CI 0.2-2.0, P = 0.004), without any change in insulin secretion. Basal and insulin-stimulated glucose oxidation were comparable in the placebo and metformin-treated groups at the end of each treatment period, as was the SSPG concentration. However, both systolic and diastolic blood pressures fell significantly following metformin administration as compared to treatment with placebo.

CONCLUSIONS

These results indicate that metformin administration to patients with IGT is associated with enhanced glucose disposal at baseline insulin concentrations and a fall in blood pressure. In contrast, neither glucose oxidation nor glucose disposal were increased in association with metformin treatment under conditions of physiological hyperinsulinaemia.

A risk-benefit assessment of metformin in type 2 diabetes mellitus

Metformin has been used for over 40 years as an effective glucose-lowering agent in type 2 (noninsulin-dependent) diabetes mellitus. Typically it reduces basal and postprandial hyperglycaemia by about 25% in more than 90% of patients when either given alone or coadministered with other therapies including insulin during a programme of managed care. Metformin counters insulin resistance and offers benefits against many features of the insulin resistance syndrome (Syndrome X) by preventing bodyweight gain, reducing hyperinsulinaemia and improving the lipid profile. In contrast to sulphonylureas, metformin does not increase insulin secretion or cause serious hypoglycaemia. Treatment of type 2 diabetes mellitus with metformin from diagnosis also offers greater protection against the chronic vascular complications of type 2 diabetes mellitus. The most serious complication associated with metformin is lactic acidosis which has an incidence of about 0.03 cases per 1000 patients years of treatment and a mortality risk of about 0.015 per 1000 patient-years. Most cases occur in patients who are wrongly prescribed the drug, particularly patients with impaired renal function (e.g. serum creatinine level > 130 micromol/L or > 1.5 g/L). Other major contraindications include congestive heart failure, hypoxic states and advanced liver disease. Serious adverse events with metformin are predictable rather than spontaneous and are potentially preventable if the prescribing guidelines are respected. Gastrointestinal adverse effects, notably diarrhoea, occur in less than 20% of patients and remit when the dosage is reduced. The life-threatening risks associated with metformin are rare and could mostly be avoided by strict adherence to the prescribing guidelines. Given the 4 decades of clinical experience with metformin, its antihyperglycaemic efficacy and benefits against Syndrome X, metformin offers a very favourable risk-benefit assessment when compared with the chronic morbidity and premature mortality among patients with type 2 diabetes mellitus.

Inhibitory action of insulin-sensitizing agents on calcium channels in smooth muscle cells from resistance arteries of guinea-pig

1. The actions of troglitazone, pioglitazone, metformin and bezafibrate, agents that improve insulin-resistance, on voltage-dependent Ca2+ channels in arterial smooth muscle cells were examined by use of the conventional and nystatin-perforated whole-cell clamp methods. Single cells were freshly isolated from resistance mesenteric arteries of guinea-pigs. The actions of these agents on 77 mM K+-induced contraction of the isolated arteries were also examined with the use of isometric tension recording. 2. The thiazolidinedione derivatives, troglitazone and pioglitazone, inhibited whole-cell Ca2+ currents in a dose-dependent manner with dissociation constants of 3.0 microM and 44.9 microM and Hill coefficients of 0.61 and 0.68, respectively. These two agents inhibited the 77 mM K+-induced contraction with similar potencies as those inhibiting the Ca2+ currents. Metformin and bezafibrate had no apparent effects on the Ca2+ current or high K+-induced contraction. 3. The inhibitory action of troglitazone on Ca2+ currents was not affected by the command potential, the holding potential, or the stimulation frequency, suggesting that its mode of the action differs from that of known organic Ca2+ channel antagonists. 4. The inhibitory action of troglitazone on Ca2+ currents was not affected by the addition of insulin to, or the removal of glucose from, the solutions. 5. In conclusion, the thiazolidinedione derivatives directly inhibited the voltage-dependent Ca2+ channels in a different manner from that of organic Ca2+ channel antagonists. This inhibitory action on Ca2+ channels was not a common feature of insulin-sensitizing agents.

Cardiovascular actions of chronic intracerebroventricular administration of metformin in normotensive rats

Acute intracerebroventricular administration of the antihyperglycaemic agent metformin (0.25-1 mg) elicits sympathoinhibitory responses in spontaneously hypertensive rats. However, cardiovascular actions of chronic intracerebroventricular metformin administration are unknown. To define the dose-response relationship during chronic intracerebroventricular metformin administration, mean arterial pressure, heart rate, and locomotor activity were measured continuously by radiotelemetry in 40 normotensive rats. After a 10 day control period, an intracerebroventricular cannula was implanted and connected to an osmotic minipump which delivered metformin in the following doses: 0 [saline]. 0.01, 0.1, 1, and 10 mg/day. LD50 was 1.5 mg/day. Metformin, 1 mg/day attenuated the nocturnal, physiological increase in mean arterial pressure (-7.3 +/- 1.6% versus before metformin), produced behavioural changes and tended to increase locomotor activity. Lower doses of intracerebroventricular metformin (0.1 and 0.01 mg/day) did not affect mean arterial pressure, heart rate or locomotor activity. In conclusion, chronic intracerebroventricular administration of high dose metformin (1.0 mg/day) attenuates the nocturnal, physiological increase in mean arterial pressure. These findings are compatible with a toxic, sympathoinhibitory action of high doses of metformin intracerebroventricularly.

An overview of metformin in the treatment of type 2 diabetes mellitus

Type 2 diabetes mellitus results from impaired insulin secretion and reduced peripheral insulin sensitivity. Treatment options include diet, oral antihyperglycemic agents, and insulin. Metformin, an oral biguanide, ameliorates hyperglycemia by improving peripheral sensitivity to insulin, and reducing gastrointestinal glucose absorption and hepatic glucose production. Unlike sulfonylureas, it does not stimulate insulin secretion, aggravate hyperinsulinemia, or cause hypoglycemia or weight gain (weight stabilizes or decreases). It also has beneficial effects on serum lipid profiles. In lean or overweight type 2 diabetic patients uncontrolled by diet, metformin monotherapy significantly improves glycemic control, compared with placebo, and to similar extents as sulfonylurea monotherapy. In secondary sulfonylurea failure, combination metformin-sulfonylurea treatment significantly improves glycemic control beyond that achieved with either agent along. Metformin-sulfonylurea also appears to be as effective as insulin or insulin plus sulfonylurea, suggesting that such combination therapy may obviate or substantially delay insulin therapy. Limited data suggest that metformin-insulin therapy may improve glycemic control, possibly reducing insulin requirements, in type 2 diabetic patients uncontrolled by insulin alone following secondary sulfonylurea failure. Gastrointestinal side effects are common, but usually tolerated. Lactic acidosis risk is minimal, provided that contraindications, particularly renal impairment, and prescribing guidelines are respected. Aside from elevated plasma metformin levels with cimetidine and synergistic hypoglycemia with sulfonylureas, few interactions occur. Thus, metformin is safe and effective both as monotherapy or in combination with other antihyperglycemic agents in type 2 diabetic patients requiring additional glycemic control and may be advantageous when weight control is desirable and/or hyperlipidemia exists.

Acute sympathoinhibitory actions of metformin in spontaneously hypertensive rats

Chronic treatment with the antihyperglycemic agent metformin prevents hypertension in spontaneously hypertensive rats. This effect has been ascribed to normalization of plasma insulin levels. However, whether metformin affects arterial pressure via changes in sympathetic nerve activity is unknown. Therefore, the objective of this study was to examine whether acute administration of metformin produces changes in mean arterial pressure, heart rate, or efferent renal sympathetic nerve activity in spontaneously hypertensive rats. Rats were anesthetized with alphaxalone-alphadolone (Saffan), paralyzed with pancuronium, and artificially ventilated. Intravenous administration of metformin (0, 1, 10, 100 mg/kg) produced dose-dependent reversible decreases in mean arterial pressure, heart rate, and efferent renal sympathetic nerve activity that were not affected by arterial or cardiopulmonary baroreceptor denervation, nitric oxide synthase inhibition by N(omega)-nitro-L-arginine methyl ester, or cyclooxygenase inhibition by indomethacin. Metformin given into the lateral cerebral ventricle (250, 500, 1000 microg) produced dose-dependent decreases in mean arterial pressure, heart rate, and efferent renal sympathetic nerve activity in doses that caused no changes when given intravenously. The sympathoinhibitory response to intracerebroventricular administration of metformin was not affected by alpha2-adrenoceptor blockade by intracerebroventricular yohimbine. We conclude that metformin has acute sympathoinhibitory effects (decreased arterial pressure, heart rate, and efferent renal sympathetic nerve activity) that are produced by a direct central nervous system site of action.

Cardiovascular effects of oral hypoglycaemic drugs

1. There is increasing evidence that sulfonylurea and biguanide oral hypoglycaemic drugs have cardiovascular effects and influence risk factors for cardiovascular disease in patients with non-insulin-dependent diabetes because of actions that are unrelated to alterations in glycaemic control. 2. While sulfonylureas may have anti-arrhythmic effects following myocardial ischaemia, there is concern that their action on vascular ATP-sensitive potassium channels may contribute to elevated blood pressure and enhanced vascular responsiveness. 3. In contrast to sulfonylureas, metformin (a biguanide) appears to reduce blood pressure and have beneficial effects on plasma lipoproteins by reducing low-density lipoprotein cholesterol and possibly increasing high-density lipoprotein cholesterol levels. 4. The pharmacological basis and clinical significance of these effects of sulfonylureas and biguanides require further investigation.

Effects of metformin treatment on glucose transporter proteins in subcellular fractions of skeletal muscle in (fa/fa) Zucker rats

1. The present study was designed to clarify the cellular mechanism through which the antihyperglycaemic drug, metformin, exerts its effects. For this purpose the contents of glucose transporter protein isoforms GLUT1 and GLUT4 were measured in plasma membrane and intracellular membrane fractions of skeletal muscle obtained from genetically obese, insulin-resistant Zucker rats. 2. Hindlimb muscles were dissected from metformin-treated (300 mg kg-1 day-1, p.o., for 12 days) and control rats in basal treatment state, and after acute stimulation with insulin (22 u kg-1, i.p.). Since metformin treatment reduces food intake, we also used a pair-fed control group to investigate the effects of altered insulinaemia per se. Glucose transporter levels were analysed by Western blot and slot blot-techniques. In addition, 2-deoxy-[14C]-glucose uptake in isolated muscle strips was evaluated. 3. No changes were noted in the contents of GLUT1 proteins in any of the subcellular fractions after metformin treatment. The contents of GLUT4 in subcellular fractions were not altered in the basal treatment state. After acute insulin exposure the content of GLUT4 in the intracellular membrane fraction declined significantly in the metformin-treated group, while no significant effect was seen in the plasma membrane fraction. In agreement with these results, metformin treatment did not alter 2-deoxyglucose uptake into isolated muscle strips. 4. In conclusion, the present study does not support the concept that metformin would enhance translocation of glucose transporter proteins from the intracellular compartment to the plasma membrane in skeletal muscle in vivo.

Metformin. A review of its pharmacological properties and therapeutic use in non-insulin-dependent diabetes mellitus

The biguanide metformin (dimethylbiguanide) is an oral antihyperglycaemic agent used in the management of non-insulin-dependent diabetes mellitus (NIDDM). It reduces blood glucose levels, predominantly by improving hepatic and peripheral tissue sensitivity to insulin without affecting the secretion of this hormone. Metformin also appears to have potentially beneficial effects on serum lipid levels and fibrinolytic activity, although the long term clinical implications of these effects are unclear. Metformin possesses similar antihyperglycaemic efficacy to sulphonylureas in obese and nonobese patients with NIDDM. Additionally, interim data from the large multicentre United Kingdom Prospective Diabetes Study (UKPDS) indicated similar antihyperglycaemic efficacy for metformin and insulin in newly diagnosed patients with NIDDM. Unlike the sulphonylureas and insulin, however, metformin treatment is not associated with increased bodyweight. Addition of metformin to existing antidiabetic therapy confers enhanced antihyperglycaemic efficacy. This may be of particular use in improving glycaemic control in patients with NIDDM not adequately controlled with sulphonylurea monotherapy, and may serve to reduce or eliminate the need for daily insulin injections in patients with NIDDM who require this therapy. The acute, reversible gastrointestinal adverse effects seen with metformin may be minimised by administration with or after food, and by using lower dosages, increased slowly where necessary. Lactic acidosis due to metformin is rare, and the risk of this complication may be minimised by observance of prescribing precautions and contraindications intended to avoid accumulation of the drug or lactate in the body. Unlike the sulphonylureas, metformin does not cause hypoglycaemia. Thus, metformin is an effective antihyperglycaemic agent which appears to improve aberrant plasma lipid and fibrinolytic profiles associated with NIDDM. Possible long term clinical benefits of this drug with regard to cardiovascular mortality and morbidity are not yet established but are being assessed in a major ongoing study. Since metformin does not promote weight gain or hypoglycaemia it should be considered first-line pharmacotherapy in obese patients with NIDDM inadequately controlled by nonpharmacological measures. Metformin appears similarly effective for the pharmacological management of NIDDM in nonobese patients.