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

Fulminant lactic acidosis in two patients with Type 2 diabetes treated with metformin

Lactic acidosis is a known adverse risk of metformin treatment. We report two cases in whom fulminant lactic acidosis developed during treatment. There were no contraindications to metformin treatment and both were admitted with abdominal discomfort for some days, causing dehydration. Both patients had renal failure on admission, developed multiple organ failure and both suffered a massive stroke. One patient died and the other survived but is severely disabled. We suggest, in both cases, that acute renal failure developed as a result of dehydration, causing metformin accumulation and lactic acidosis. We recommend that all patients on metformin should consider discontinuation of metformin treatment in the event of a severe medical condition causing dehydration.

Signaling pathways involved in human vascular smooth muscle cell proliferation and matrix metalloproteinase-2 expression induced by leptin: inhibitory effect of metformin

Accumulating evidence suggests that high concentrations of leptin observed in obesity and diabetes may contribute to their adverse effects on cardiovascular health. Metformin monotherapy is associated with reduced macrovascular complications in overweight patients with type 2 diabetes. It is uncertain whether such improvement in the cardiovascular outcome is related to specific vasculoprotective effects of this drug. In the present study, we determined the effect of leptin on human aortic smooth muscle cell (HASMC) proliferation and matrix metalloproteinase (MMP)-2 expression, the signaling pathways mediating these effects, and the modulatory effect of metformin on these parameters. Incubation of HASMCs with leptin enhanced the proliferation and MMP-2 expression in these cells and increased the generation of intracellular reactive oxygen species (ROS). These effects were abolished by vitamin E. Inhibition of NAD(P)H oxidase and protein kinase C (PKC) suppressed the effect of leptin on ROS production. In HASMCs, leptin induced PKC, extracellular signal-regulated kinase (ERK)1/2, and nuclear factor-kappaB (NF-kappaB) activation and inhibition of these signaling pathways abrogated HASMC proliferation and MMP-2 expression induced by this hormone. Treatment of HASMCs with metformin decreased leptin-induced ROS production and activation of PKC, ERK1/2, and NF-kappaB. Metformin also inhibited the effect of leptin on HASMC proliferation and MMP-2 expression. Overall, these results demonstrate that leptin induced HASMC proliferation and MMP-2 expression through a PKC-dependent activation of NAD(P)H oxidase with subsequent activation of the ERK1/2/NF-kappaB pathways and that therapeutic metformin concentrations effectively inhibit these biological effects. These results suggest a new mechanism by which metformin may improve cardiovascular outcome in patients with diabetes.

Do risk factors for lactic acidosis influence dosing of metformin?

BACKGROUND

Metformin is commonly prescribed to treat type 2 diabetes mellitus, however it is associated with the potentially lethal condition of lactic acidosis. Prescribing guidelines have been developed to minimize the risk of lactic acidosis development, although some suggest they are inappropriate and have created confusion amongst prescribers. The aim of this study was to investigate whether metformin dose was influenced by the presence of risk factors for lactic acidosis.

METHODS

The study was prospective, and retrieved information from patients admitted to hospital who were prescribed metformin at their time of admission.

RESULTS

Eighty-three patients were included in the study, 60 of whom had a least one risk factor for lactic acidosis. Of those 60 patients, 78.3% had a dose adjustment, with renal impairment, hepatic impairment, surgery and use of radiological contrast media--the risk factors most likely to result in a dose adjustment. When dose adjustments did occur, metformin was withheld on 88.7% of occasions.

CONCLUSION

Metformin dose was influenced by the presence of risk factors for lactic acidosis, although it was dependent upon the number and particular risk factor/s present.

Efficacy, dose-response relationship and safety of once-daily extended-release metformin (Glucophage XR) in type 2 diabetic patients with inadequate glycaemic control despite prior treatment with diet and exercise: results from two double-blind, placebo-controlled studies

AIM

The efficacy, dose-response relationships and safety of an extended-release formulation of metformin (Glucophage) XR) were evaluated in two double-blind, randomized, placebo-controlled studies of 24 and 16 weeks' duration, in patients with inadequate glycaemic control despite diet and exercise. Protocol 1 provided an evaluation of metformin XR at a commonly used dosage. Protocol 2 evaluated different dosages of metformin XR.

METHODS

In Protocol 1, 240 patients were randomized to receive metformin XR 1000 mg once daily. or placebo in a 2:1 ratio for 12 weeks (patients could receive metformin XR 1500 mg during weeks 12-24 if required). In Protocol 2, 742 patients were randomized to receive metformin XR 500 mg once daily, 1000 mg once daily, 1500 mg once daily, 2000 mg once daily, 1000 mg twice daily or placebo for 16 weeks. The primary endpoint in each study was the change from baseline in HbA(1C) at 12 weeks (Protocol 1) or 16 weeks (Protocol 2).

RESULTS

Metformin XR reduced HbA(1C) in Protocol 1, with mean treatment differences for 1000 mg once daily vs. placebo of -0.7% at 12 weeks and -0.8% at 24 weeks (p < 0.001 for each). In Protocol 2, a clear dose-response relationship was evident at doses up to 1500 mg, with treatment differences vs. placebo of -0.6% (500 mg once daily), -0.7% (1000 mg once daily), -1.0% (1500 mg once daily) and -1.0% (2000 mg once daily). The efficacy of metformin XR 2000 mg once daily and 1000 mg twice daily were similar (mean treatment differences vs. placebo in HbA(1C) were -1.0% and -1.2%, respectively). More patients achieved HbA(1C) < 7.0% with metformin XR vs. placebo in Protocol 1 (29% vs. 14% at 12 weeks) and with once-daily metformin XR in Protocol 2 (up to 36% vs. 10% at 16 weeks). No significant changes in fasting insulin or body weight occurred. Total and low-density lipoprotein (LDL)-cholesterol improved (p < 0.05-p < 0.001) in metformin XR groups in Protocol 2. Metformin XR was well tolerated; gastrointestinal side effects were more common with metformin XR vs. placebo, but few patients withdrew for this reason (1.3% vs. 1.3% in Protocol 1 and 1.6% vs. 0.9% in Protocol 2).

CONCLUSIONS

Once-daily metformin XR presents an effective and well-tolerated therapeutic option for delivering metformin in a convenient manner, which supports good compliance with therapy.

Avandamet: combined metformin-rosiglitazone treatment for insulin resistance in type 2 diabetes

Insulin resistance is a major endocrinopathy underlying the development of hyperglycaemia and cardiovascular disease in type 2 diabetes. Metformin (a biguanide) and rosiglitazone (a thiazolidinedione) counter insulin resistance, acting by different cellular mechanisms. The two agents can be used in combination to achieve additive glucose-lowering efficacy in the treatment of type 2 diabetes, without stimulating insulin secretion and without causing hypoglycaemia. Both agents also reduce a range of atherothrombotic factors and markers, indicating a lower cardiovascular risk. Early intervention with metformin is already known to reduce myocardial infarction and increase survival in overweight type 2 patients. Recently, a single-tablet combination of metformin and rosiglitazone, Avandamet, has become available. Avandamet is suitable for type 2 diabetic patients who are inadequately controlled by monotherapy with metformin or rosiglitazone. Patients already receiving separate tablets of metformin and rosiglitazone may switch to the single-tablet combination for convenience. Also, early introduction of the combination before maximal titration of one agent can reduce side effects. Use of Avandamet requires attention to the precautions for both metformin and rosiglitazone, especially renal, cardiac and hepatic competence. In summary, Avandamet is a single-tablet metformin-rosiglitazone combination that doubly targets insulin resistance as therapy for hyperglycaemia and vascular risk in type 2 diabetes.

Improved glycemic control without weight gain using triple therapy in type 2 diabetes

OBJECTIVE

To evaluate the safety and effectiveness of triple therapy using insulin, metformin, and a thiazolidinedione following a course of dual therapy using insulin and metformin or insulin and a thiazolidinedione in type 2 diabetes.

RESEARCH DESIGN AND METHODS

Twenty-eight type 2 diabetic subjects using insulin monotherapy (baseline HbA(lc) level 8.5%) who had been randomly assigned to insulin (INS) and metformin (MET) (INS + MET, n = 14) or INS and the thiazolidinedione troglitazone (TGZ) (INS + TGZ, n = 14) (dual therapy) for 4 months were given INS, MET, and TGZ (triple therapy: INS + MET, add TGZ; or INS + TGZ, add MET) for another 4 months. The INS dose was not increased.

RESULTS

HbA(1c) levels decreased in both groups during dual therapy and improved further during triple therapy (INS + MET 7.0 +/- 0.8, INS + TGZ 6.2 +/- 0.8, P < 0.0001; INS + MET, add TGZ 6.1 +/- 0.4%, P < 0.001; INS + TGZ, add MET 5.8 +/- 0.6%, P < 0.05; and INS + TGZ vs. INS + MET, P = 0.02). Significant reductions in total daily insulin dose occurred in the INS + TGZ (-14.1 units, P < 0.0001), INS + TGZ add MET (-13.7 units, P < 0.01), and the INS + MET add TGZ groups (-17.3 units, P < 0.003), but not in the INS + MET group (-3.2 units) (INS + TGZ vs. INS + MET P < 0.05). Subjects in the INS + TGZ group experienced significant weight gain (4.4 +/- 2.7 kg, P < 0.0005). No weight gain occurred in the INS + MET, INS + MET add TGZ, and INS + TGZ add MET groups.

CONCLUSIONS

Triple therapy using INS, MET, and TGZ resulted in lower HbA(lc) levels and total daily insulin dose than during dual therapy. The use of triple therapy resulted in 100% of subjects achieving an HbA(lc) <7.0%, while decreasing the dose of INS. Weight gain was avoided when MET therapy preceded the addition of TGZ therapy. The addition of TGZ resulted in the greatest reductions in HbA(lc) levels and insulin dose. Triple therapy using INS, MET, and a thiazolidinedione (such as TGZ) can be a safe and effective treatment in type 2 diabetes.

Gastrointestinal tolerability of extended-release metformin tablets compared to immediate-release metformin tablets: results of a retrospective cohort study

OBJECTIVE

Metformin, a biguanide antihyperglycemic medication, lowers blood glucose in patients with type 2 diabetes with minimal risk of hypoglycemia. Most common side effects include diarrhea, nausea and vomiting. Extended-release metformin (Glucophage XR)*, a once-daily tablet using the patented GelShield Diffusion System release mechanism, may be better tolerated than immediate-release metformin (Glucophage). This retrospective chart review examined the overall gastrointestinal (GI) tolerability of both formulations.

RESEARCH DESIGN AND METHODS

Patient charts were reviewed and data were collected from October 2001 to May 2002. Adult patients with type 2 diabetes started on extended-release metformin (metformin-XR) or switched from immediate-release metformin to metformin-XR within the previous 2 years were eligible for inclusion in the metformin-XR cohort. Patients started on immediate-release metformin within the previous 2 years were eligible for inclusion in the immediate-release metformin cohort. Previous experience of GI side effects while taking immediate-release metformin did not prevent inclusion in either cohort, though patients with significant underlying GI disease or moderate to severe hepatic or renal impairment were excluded. GI tolerability was assessed during the first year of treatment with immediate-release metformin or metformin-XR. Primary endpoints were overall GI tolerability and frequency of diarrhea during the first year of treatment.

RESULTS

A total of 471 patients' charts were reviewed and data were collected from four diabetes clinics; 310 (metformin-XR) and 158 (immediate-release metformin) eligible patients were included. Patients were, on average, 56 years old, and overweight (mean body mass index 33 kg/m2). The majority of patients were Caucasian (50%), Hispanic (24%) or Black (19%). Mean daily doses were 1258 mg (range 500-2500 mg) for metformin-XR and 1282 mg (range 500-2550 mg) for immediate-release metformin. About 25% of the metformin-XR cohort had been switched from immediate-release metformin due to a history of GI adverse events (AE). Despite this, the frequency of any GI AE was similar between metformin-XR and immediate release metformin (11.94 vs. 11.39%, p = 0.86). The incidence of individual GI AE also did not differ significantly between cohorts. In a cohort of 205 patients started on immediate-release metformin and switched to metformin-XR, the frequency of any GI AE was 26.34% (while taking immediate release metformin; n = 205) vs. 11.71% (after switching to metformin-XR; n = 205) (p = 0.0006) and the frequency of diarrhea was 18.05% (while taking immediate-release metformin) vs. 8.29% (after switching to metformin-XR) (p = 0.0084).

CONCLUSIONS

In this retrospective chart review, patients switched from immediate-release metformin to metformin-XR experienced fewer GI side effects on comparable doses of the extended-release metformin.

Metformin hydrochloride in the treatment of type 2 diabetes mellitus: a clinical review with a focus on dual therapy

BACKGROUND

Type 2 diabetes mellitus typically involves abnormal beta-cell function that results in relative insulin deficiency, insulin resistance accompanied by decreased glucose transport into muscle and fat cells, and increased hepatic glucose output, all of which contribute to hyperglycemia.

OBJECTIVE

This review examines the pharmacology, pharmacokinetics, drug-interaction potential, adverse effects, and dosing guidelines for metformin hydrochloride, a biguanide agent for the treatment of type 2 diabetes. Clinical trial data are reviewed, including efficacy and tolerability information, with a focus on studies of dual metformin therapy (metformin plus another oral agent or insulin) published from 1998 to the present. Pharmacoeconomic considerations are also discussed.

METHODS

Primary research and review articles were identified through a search of MEDLINE (1966-May 2003) and International Pharmaceutical Abstracts (1970-May 2003) using the terms metformin and/or Glucophage. Web of Science (1995-May 2003) was used to search for additional abstracts. The package inserts for metformin and metformin combination products were consulted. All identified articles and abstracts were assessed for relevance, and all relevant information was included. Priority was given to the primary medical literature and clinical trial reports.

RESULTS

Metformin is the only currently available oral antidiabetic/hypoglycemic agent that acts predominantly by inhibiting hepatic glucose release. Because patients with type 2 diabetes often have excess hepatic glucose output, use of metformin is effective in lowering glycosylated hemoglobin (HbA1c) by 1 to 2 percentage points when used as monotherapy or in combination with other blood glucose-lowering agents or insulin. Other metabolic variables (eg, dyslipidemia, fibrinolysis) may be improved with the use of metformin. Body weight is often maintained or slightly reduced from baseline. Metformin is well tolerated and is associated with few clinically deleterious adverse events. The most important and potentially life-threatening adverse event associated with its use is lactic acidosis, which occurs very rarely.

CONCLUSIONS

Metformin has multiple benefits in patients with type 2 diabetes. It can effectively lower HbA1c values, positively affect lipid profiles, and improve vascular and hemodynamic indices. Adverse effects are generally tolerable and self-limiting. The availability of products combining metformin with a sulfonylurea or rosiglitazone has expanded the array of therapies for the management of type 2 diabetes.

Metformin and vascular protection: a diabetologist's view

The diabetologist's short-term priority is often to gain rapid control of severe and symptomatic hyperglycaemia, with the longer term objective of preventing or delaying the onset of the debilitating and life-threatening complications that result from continued poor glycaemic control. Indeed, guidelines for the management of type 2 diabetes are centred firmly on measures of glycaemic control, based on evidence from the landmark UK Prospective Diabetes Study and Diabetes Control and Complications Trial. Nevertheless, we must remember that most type 2 diabetic patients ultimately die from a cardiovascular cause. A comprehensive approach is needed, where effective control of blood glucose takes place alongside aggressive management of cardiovascular risk factors. A substantial database of clinical evidence, including the ground-breaking UK Prospective Diabetes Study, underpins the place of metformin both as an effective oral antihyperglycaemic agent and for reducing the risk of morbid cardiovascular events.

Effects of rosiglitazone maleate when added to a sulfonylurea regimen in patients with type 2 diabetes mellitus and mild to moderate renal impairment: A post hoc analysis

BACKGROUND

Patients with type 2 diabetes mellitus (DM) and renal impairment whose disease is inadequately controlled on a sulfonylurea (SU) have limited oral combination treatment options.

OBJECTIVE

This post hoc analysis assesses the efficacy and tolerability of the insulin sensitizer rosiglitazone maleate (RSG) when added to an SU treatment regimen in patients with type 2 DM with mild to moderate renal impairment that is inadequately controlled by SU monotherapy.

METHODS

Data were pooled from 3 randomized, double-blind, placebo-controlled, parallel-group studies in which RSG or placebo was added to an SU (glibenclamide, gliclazide, or glipizide) treatment regimen for a period of 6 months. Patients were subcategorized as having mild to moderate renal impairment or normal renal function based on a baseline creatinine clearance rate of 30 to 80 mL/min or >80 mL/min, respectively, as estimated by the Cockcroft-Gault equation.

RESULTS

The population studied comprised 824 patients, 62% men and 38% women, aged 32 to 81 years, of whom 301 had mild to moderate renal impairment and 523 had normal renal function. In patients with and without renal impairment, glycemia was improved in the SU + RSG-treated group compared with the SU + placebo-treated group. The observed treatment differences between the groups were -2.6 mmol/L for fasting plasma glucose and -1.1% for glycosylated hemoglobin (for both renally impaired and nonimpaired patients). For patients receiving SU + RSG, little difference in the safety profile was found between patients with and without renal impairment.

CONCLUSION

RSG was effective and well tolerated when added to SU therapy in this population of patients with mild to moderate renal impairment.

Efficacy of glyburide/metformin tablets compared with initial monotherapy in type 2 diabetes

Many patients with type 2 diabetes fail to achieve or maintain the American Diabetes Association's recommended treatment goal of glycosylated hemoglobin levels. This multicenter, double-blind trial enrolled patients with type 2 diabetes who had inadequate glycemic control [glycosylated hemoglobin A(1C) (A1C), >7% and <12%) with diet and exercise alone to compare the benefits of initial therapy with glyburide/metformin tablets vs. metformin or glyburide monotherapy. Patients (n = 486) were randomized to receive glyburide/metformin tablets (1.25/250 mg), metformin (500 mg), or glyburide (2.5 mg). Changes in A1C, fasting plasma glucose, fructosamine, serum lipids, body weight, and 2-h postprandial glucose after a standardized meal were assessed after 16 wk of treatment. Glyburide/metformin tablets caused a superior mean reduction in A1C from baseline (-2.27%) vs. metformin (-1.53%) and glyburide (-1.90%) monotherapy (P = 0.0003). Glyburide/metformin also significantly reduced fasting plasma glucose and 2-h postprandial glucose values compared with either monotherapy. The final mean doses of glyburide/metformin (3.7/735 mg) were lower than those of metformin (1796 mg) and glyburide (7.6 mg). First-line treatment with glyburide/metformin tablets provided superior glycemic control over component monotherapy, allowing more patients to achieve American Diabetes Association treatment goals with lower component doses in drug-naive patients with type 2 diabetes.

Differential effects of metformin on bile salt absorption from the jejunum and ileum

AIMS

The antidiabetic drug metformin is often associated with a small reduction in total circulating cholesterol, but the mechanism responsible is unknown. As bile salts contribute significantly to cholesterol homeostasis, this study has investigated the effect of metformin on the absorption of bile salts by the jejunum and ileum, and their transfer into bile.

METHODS

Sodium-[1-14C]-glycocholate was administered into the jejunum or ileum of anaesthetized rats with and without metformin (250 mg/kg). Appearance of 14C-glycocholate in plasma and bile was followed for 150 min.

RESULTS

Absorption of 14C-glycocholate from the ileum, which is a high-capacity active process, was 10-fold greater than absorption from the jejunum, which is mainly a passive process. Metformin increased threefold the absorption of 14C-glycocholate from the jejunum. Metformin similarly increased the appearance of jejunal 14C-glycocholate in plasma and bile. In contrast to the jejunum, absorption of 14C-glycocholate from the ileum was suppressed by more than half with metformin. This was associated with corresponding reductions of 14C-glycocholate in plasma and bile.

DISCUSSION

Thus, metformin induced a large suppression of active bile salt absorption from the ileum compared with a small increase in passive absorption from the jejunum. This suggests that the ileal effect of metformin to reduce overall bile salt absorption could contribute to the modest cholesterol-lowering effect of this drug.

Metformin-associated lactic acidosis after elective cervical spine fusion: a case report

STUDY DESIGN

A case of metformin-associated lactic acidosis after elective spinal surgery is reported.

OBJECTIVE

To inform spinal surgeons of this potentially fatal side effect and make them aware that metformin should be stopped 48 hours before surgery.

SUMMARY OF BACKGROUND DATA

Metformin is a commonly used oral hypoglycemic agent used in the treatment of non-insulin-dependent diabetes mellitus. A rare side effect of metformin is lactic acidosis, which has a 50% mortality rate. Risk factors for metformin-associated lactic acidosis include renal, hepatic, and cardiac failure. Two cases have been reported in postsurgical patients. No cases of this disorder have been reported after orthopedic procedures.

METHODS

A patient who developed metformin-associated lactic acidosis after cervical spinal fusion is presented.

RESULTS

Recognition of the cause and aggressive medical management led to resolution of the lactic acidosis. Subsequent surgery was uneventful when metformin was discontinued more than 48 hours before surgery.

CONCLUSION

Spinal surgeons should be aware of this preventable, potentially fatal side effect and stop metformin 48 hours before surgery.

Comparison of insulin monotherapy and combination therapy with insulin and metformin or insulin and troglitazone in type 2 diabetes

OBJECTIVE

To evaluate the safety and efficacy of treatment with insulin alone, insulin plus metformin, or insulin plus troglitazone in individuals with type 2 diabetes.

RESEARCH DESIGN AND METHODS

A total of 88 type 2 diabetic subjects using insulin monotherapy (baseline HbA(lc) 8.7%) were randomly assigned to insulin alone (n = 31), insulin plus metformin (n = 27), or insulin plus troglitazone (n = 30) for 4 months. The insulin dose was increased only in the insulin group. Metformin was titrated to a maximum dose of 2,000 mg and troglitazone to 600 mg.

RESULTS

HbA(lc) levels decreased in all groups, the lowest level occurring in the insulin plus troglitazone group (insulin alone to 7.0%, insulin plus metformin to 7.1%, and insulin plus troglitazone to 6.4%, P < 0.0001). The dose of insulin increased by 55 units/day in the insulin alone group (P < 0.0001) and decreased by 1.4 units/day in the insulin plus metformin group and 12.8 units/day in the insulin plus troglitazone group (insulin plus metformin versus insulin plus troglitazone, P = 0.004). Body weight increased by 0.5 kg in the insulin plus metformin group, whereas the other two groups gained 4.4 kg (P < 0.0001 vs. baseline). Triglyceride and VLDL triglyceride levels significantly improved only in the insulin plus troglitazone group. Subjects taking metformin experienced significantly more gastrointestinal side effects and less hypoglycemia.

CONCLUSIONS

Aggressive insulin therapy significantly improved glycemic control in type 2 diabetic subjects to levels comparable with those achieved by adding metformin to insulin therapy. Troglitazone was the most effective in lowering HbA(lc), total daily insulin dose, and triglyceride levels. However, treatment with insulin plus metformin was advantageous in avoiding weight gain and hypoglycemia.

Metformin in patients with type 2 diabetes mellitus: reconsideration of traditional contraindications

BACKGROUND: The strict limiting criteria for the use of metformin in diabetes mellitus stem largely from reports, in the 1970s, of mortality and lactic acidosis associated with phenformin. Data about metformin are less clear and are based mainly on case reports. The aim of this study was to evaluate the safety of continued use of metformin in patients with contraindications to this agent. PATIENTS: Some 393 patients with type 2 diabetes mellitus (serum creatinine 130-220 &mgr;mol/l) were studied. Among them were 266 patients with coronary heart disease (CHD), 94 with congestive heart failure (CHF), and 91 with chronic obstructive pulmonary disease (COPD), all of whom had been treated with metformin. The patients were randomized to either continue or to stop metformin and were then followed for 4 years. RESULTS: Analysis was by intention-to-treat. The patients who stopped taking metformin showed a rise in body mass index and in hemoglobin A1c significantly greater than those who continued the drug. There were no cases of lactic acidosis. Lactic acid values did not differ in the two groups and correlated only with serum creatinine and body mass index. Microvascular diabetic complications, cardiovascular events, and cardiovascular and total mortality were identical in the two groups. CONCLUSIONS: Diabetic patients who are treated with metformin and who tolerate the drug well may continue taking it, even when mild renal impairment develops, possibly up to serum creatinine levels of 220 &mgr;mol/l. There is also no apparent reason why patients with CHD, CHF, and COPD should discontinue metformin.

Rosiglitazone: a review of its use in the management of type 2 diabetes mellitus

Rosiglitazone, a thiazolidinedione with a different side chain from those of troglitazone and pioglitazone, reduces plasma glucose levels and glucose production and increases glucose clearance in patients with type 2 diabetes mellitus. Insulin sensitivity, pancreatic beta-cell function and surrogate markers of cardiovascular risk factors are significantly improved by rosiglitazone. Double-blind trials of 8 to 26 weeks of rosiglitazone 4 or 8 mg/day monotherapy indicate significant decreases in fasting plasma glucose (-2 to -3 mmol/L with 8 mg/day) and glycosylated haemoglobin levels [HbA(1c); -0.6 to -0.7% (-0.8 to -1.1% in drug-naive patients) with 8 mg/day]. Significant decreases in hyperglycaemic markers occurred when rosiglitazone was combined with metformin (HbA(1c) -0.8 to -1.0%), a sulphonylurea (-1.4%) or insulin (-1.2%) for 26 weeks versus little change with active comparator monotherapy. Efficacy was maintained in trials of < or = 2 years, and was also apparent in various ethnic subgroups, elderly patients, and both obese and nonobese patients. Rosiglitazone is currently not indicated in combination with injected insulin. It should be administered in conjunction with diet and exercise regimens. Rosiglitazone is generally well tolerated. Despite rare individual reports of liver function abnormalities in rosiglitazone recipients, the incidence of these in clinical trials (< or = 2 years' duration) was similar to that in placebo and active comparator groups. Fluid retention associated with rosiglitazone may be the cause of the increased incidence of anaemia in clinical trials, and also means that patients should be monitored for signs of heart failure during therapy. Although bodyweight is increased overall with rosiglitazone therapy, increases are in subcutaneous, not visceral, fat; hepatic fat is decreased. The pharmacokinetic profile of rosiglitazone is not substantially altered by age or renal impairment, nor are there important drug interactions. Rosiglitazone is not indicated in patients with active liver disease or increased liver enzymes.

CONCLUSIONS

Oral rosiglitazone 4 or 8 mg/day provides significant antihyperglycaemic efficacy and is generally well tolerated, both as monotherapy and in combination with other antihyperglycaemic agents, in patients with type 2 diabetes mellitus who do not have active liver disease. Long-term data are required before conclusions can be drawn about the clinical significance of positive changes to surrogate markers of cardiovascular disease risk and improvements to pancreatic beta-cell function. Rosiglitazone significantly improves insulin sensitivity and, as such, is a welcome addition to the treatment options for patients with type 2 diabetes mellitus.

Improved glycaemic control with metformin-glibenclamide combined tablet therapy (Glucovance) in Type 2 diabetic patients inadequately controlled on metformin

AIMS

To evaluate the efficacy and safety of two dosage strengths of a single-tablet metformin-glibenclamide (glyburide) combination, compared with the respective monotherapies, in patients with Type 2 diabetes mellitus (DM) inadequately controlled by metformin monotherapy.

METHODS

In this 16-week, double-blind, multicentre, parallel-group trial, 411 patients were randomized to receive metformin 500 mg, glibenclamide 5 mg, metformin-glibenclamide 500 mg/2.5 mg or metformin-glibenclamide 500 mg/5 mg, titrated with the intention to achieve fasting plasma glucose (FPG) < or = 7 mmol/l.

RESULTS

Decreases in glycated haemoglobin (HbA1c) and FPG were greater (P < 0.05) for metformin-glibenclamide 500 mg/2.5 mg (-1.20% and -2.62 mmol/l) and 500 mg/5 mg (-0.91% and -2.34 mmol/l), compared with metformin (-0.19% and -0.57 mmol/l) or glibenclamide (-0.33% and -0.73 mmol/l). HbA1c < 7% was achieved by 75% and 64% of patients receiving metformin-glibenclamide 500 mg/2.5 mg and 500 mg/5 mg, respectively, compared with 42% for glibenclamide and 38% for metformin (P = 0.001). These benefits were achieved at lower mean doses of metformin or glibenclamide with metformin-glibenclamide 500 mg/2.5 mg and 500 mg/5 mg (1225 mg/6.1 mg and 1170 mg/11.7 mg) than with glibenclamide (13.4 mg) or metformin (1660 mg). Treatment-related serious adverse events occurred in two patients receiving glibenclamide. Plasma lipid profiles were unaffected and mean changes in body weight were < or = 1.0 kg.

CONCLUSIONS

Intensive management of Type 2 DM with a new metformin-glibenclamide combination tablet improved glycaemic control and facilitated the attainment of glycaemic targets at lower doses of metformin or glibenclamide compared with the respective monotherapies, without compromising tolerability.

Long-term glycaemic improvement after addition of metformin to insulin in insulin-treated obese type 2 diabetes patients

AIM

To assess the adjunct effect of metformin to insulin in type 2 diabetes.

METHODS

Obese and overweight type 2 diabetes patients treated with insulin for at least 1 year, and with poor glycaemic control (HbA1c > upper reference level + 2%), were included in a randomised, double-blind, placebo-controlled study. Patients were treated for 12 months with either metformin (850 mg b.i.d.) or placebo added to their usual insulin, which was stabilized during a 3-month placebo run-in period, but thereafter attempted to be unchanged.

RESULTS

Thirty-seven patients were included. Two patients dropped out during run-in. There were no differences between the metformin (n = 16) and placebo (n = 19) group at baseline. Most patients received multiple insulin injections. Metabolic control was improved by addition of metformin. Mean change in HbA1c from baseline showed highly significant difference between groups at 3, 6, 9 and 12 months. Mean change (percentage units +/- s.d.) at 12 months was -1.1 +/- 0.7% vs. + 0.3 +/- 0.8% (p < 0.001) for HbA1c and -1.4 +/- 2.1 mmol/l vs. + 0.6 +/- 2.2 mmol/l (p = 0.025) for fasting blood glucose. Mean low density lipoprotein (LDL) cholesterol change differed slightly at 6 months, but not at 12 months. There were no changes in insulin dose, blood pressure, body weight, triglycerides, total- and high density lipoprotein (HDL) cholesterol, fibrinogen, C-peptide and laboratory safety variables, including serum B12. Combination therapy was well-tolerated with the same adverse event rate as insulin alone, but more patients with diarrhoea.

CONCLUSION

Addition of metformin to insulin induced and maintained clinically significant and consistent long-term reduction of hyperglycaemia in obese, insulin-treated type 2 diabetes patients.

The relationship between metformin therapy and the fasting plasma lactate in type 2 diabetes: The Fremantle Diabetes Study

AIMS

To determine (i) which factors, including metformin, are associated with the fasting plasma lactate concentration in type 2 diabetes, and (ii) whether plasma lactate is associated with haemodynamic and metabolic effects.

METHODS

We measured fasting plasma lactate in 272 well-characterized diabetic patients from a community-based sample, 181 (67%) of whom were taking metformin with or without other therapies. Linear regression analysis was used to identify predictors, including metformin therapy, of the plasma lactate, and to investigate associations between plasma lactate and resting pulse rate and serum bicarbonate. Factor analysis assessed independent relationships between groups of cosegregating variables.

RESULTS

Metformin-treated patients had higher plasma lactate concentrations than nonmetformin-treated subjects (geometric mean [s.d. range] 1.86 [1.34-2.59] vs 1.58 [1.09-2.30] mmol x l(-1), respectively; P < 0.001). In a linear regression model, plasma glucose, BMI and metformin use (but not dose) were independently associated with plasma lactate (P < or = 0.028); after adjustment for the former two variables, metformin-treated patients had a mean plasma lactate 0.16 mmol l-1 greater than in subjects not taking the drug. Factor analysis revealed that plasma lactate, plasma glucose, BMI and pulse rate cosegregated but serum bicarbonate was not in this grouping.

CONCLUSIONS

The present results show that metformin therapy increases the fasting plasma lactate in ambulant patients with type 2 diabetes from a community-based cohort. From associations in the data we hypothesize that this increase reflects (i) increased sympathetic activity in patients with the metabolic syndrome (ii) increased substrate (glucose) availability and (iii) a direct metformin effect.

Contraindications to metformin therapy in patients with Type 2 diabetes--a population-based study of adherence to prescribing guidelines

AIMS

To define the number of people in Tayside, Scotland (population 349 303) with Type 2 diabetes who use metformin, the incidence of contraindications to its continued use in these people and the proportion that discontinued metformin treatment following the development of a contraindication.

METHODS

Retrospective cohort study of the incidence of contraindications to metformin in all patients with Type 2 diabetes using metformin from January 1993 to June 1995. The contraindications of acute myocardial infarction, cardiac failure, renal impairment and chronic liver disease were identified by: the regional diabetes information system, biochemistry database and hospital admissions database and a database of all encashed community prescriptions.

RESULTS

One thousand eight hundred and forty seven subjects (26.3% of those with Type 2 diabetes) redeemed prescriptions for metformin. Of these, 3.5% were admitted with an acute myocardial infarction (71 episodes); 4.2% were admitted with cardiac failure (114 episodes); 21.0% received metformin and loop diuretics for cardiac failure concurrently; 4.8% developed renal impairment; and 2.8% developed chronic liver disease. The development of contraindications rarely resulted in discontinuation of metformin, for example only 17.5% and 25% stopped metformin after admission with acute myocardial infarction and development of renal impairment, respectively. In total, 24.5% of subjects receiving metformin, 6.4% of all people with Type 2 diabetes, had contraindications to its use. There was one episode of lactic acidosis in 4600 patient years.

CONCLUSIONS

This population-based study shows that 24.5% of patients prescribed metformin have contraindications to its use. Development of contraindications rarely results in discontinuation of metformin therapy. Despite this, lactic acidosis remains rare. Diabet. Med. 18, 483-488 (2001)

Additive glucose-lowering effects of glucagon-like peptide-1 and metformin in type 2 diabetes

OBJECTIVE

The incretin hormone glucagon-like peptide-1 (GLP-1) reduces plasma glucose in type 2 diabetic patients by stimulating insulin secretion and inhibiting glucagon secretion. The biguanide metformin is believed to lower plasma glucose without affecting insulin secretion. We conducted this study to investigate the effect of a combination therapy with GLP-1 and metformin, which could theoretically be additive, in type 2 diabetic patients.

RESEARCH DESIGN AND METHODS

In a semiblinded randomized crossover study, seven patients received treatment with metformin (1,500 mg daily orally) alternating with GLP-1 (continuous subcutaneous infusion of 2.4 pmol x kg(-1) x min(-1)) alternating with a combination of metformin and GLP-1 for 48 h. Under fixed energy intake, we examined the effects on plasma glucose, insulin, C-peptide, glucagon, and appetite.

RESULTS

Fasting plasma glucose (day 2) decreased from 13.9 +/- 1 (no treatment) to 11.2 +/- 0.4 (metformin) and 11.5 +/- 0.5 (GLP-1) and further decreased to 9.4 +/- 0.7 (combination therapy) (P = 0.0005, no difference between monotherapy with GLP-1 and metformin). The 24-h mean plasma glucose (day 2) decreased from 11.8 +/- 0.5 (metformin) and 11.7 +/- 0.8 (GLP-1) to 9.8 +/- 0.5 (combination) (P = 0.02, no difference between GLP-1 and metformin). Insulin levels were similar between the three regimens, but glucagon levels were significantly reduced with GLP-1 compared with metformin (P = 0.0003). Combination therapy had no additional effect on appetite scores.

CONCLUSIONS

Monotherapy with GLP-1 and metformin have equal effects on plasma glucose and additive effects upon combination.

Optimising therapy for insulin-treated type 2 diabetes mellitus

The purpose of this article is to provide a guide to the optimal use of insulin in type 2 (non-insulin-dependent) diabetes mellitus. Based on pathophysiological considerations and a knowledge of drug actions, an individualised, targeted strategy is selected for obtaining good metabolic control without compromising well-being and quality of life. The treatment should target hyperglycaemia along with other risk factors. Insulin is indicated when adequate glycaemia can no longer be obtained with diet and oral antihyperglycaemic agents. Commonly, the oral drugs are replaced by insulin, but preferably they should be used in combination with insulin. This approach can lead to improved glycaemic control, a reduced insulin dose and counteraction of insulin-associated bodyweight gain. There may also be less hypoglycaemia with combination insulin/oral therapy as compared with insulin monotherapy, as well as other benefits. Optimisation of oral drug therapy should be attempted before initiating insulin. A combination of insulin with a sulphonylurea agent is commonly used: the adjunctive effect of the sulphonylurea is dependent on pancreatic beta cell function. The combination of insulin with metformin or a thiazolidinedione is more logical as insulin resistance is targeted directly. Bedtime insulin plus metformin conferred the most benefits among several options investigated in a randomised 1-year study. The combination of insulin with acarbose is a further option when there is significant postprandial hyperglycaemia. It is recommended to start with a medium- to long-acting insulin preparation at bedtime or premixed insulin before the evening meal. Changes in insulin administration can be subsequently introduced as needed, e.g. use of twice-daily premixed insulin, multiple injections of rapid-acting insulin or insulin analogues. There are many options, but limited clinical data are available to support a number of the regimens.

Potential new treatments for type 2 diabetes

The heterogeneous pathogenesis and progressive natural history of type 2 diabetes mellitus (T2DM) contrive a formidable therapeutic challenge. Dual endocrine deficits of impaired insulin action (insulin resistance) and inadequate insulin secretion create an environment of chronic hyperglycaemia and general metabolic disarray. This inflicts a heavy burden of morbidity and premature mortality from cardiovascular diseases, microvascular disorders (e.g. retinopathy and nephropathy) and neuropathic conditions. Improving glycaemic control delays the onset and reduces the severity of these long-term complications. However, even with intensive use of current antidiabetic agents more than 50% of T2DM patients suffer poor glycaemic control and 18% develop serious complications within six years of diagnosis. Clearly, there is a need for new antidiabetic agents.