Update on the therapeutic role of metformin in the management of polycystic ovary syndrome: Effects on pathophysiologic process and fertility outcomes

Influential guidelines have supported the role of metformin in the management of polycystic ovary syndrome (PCOS) for a number of years. However, regulatory approvals for this therapeutic indication are still exceptional and exist only in a few countries, including for the originator, Glucophage®. PCOS is an insulin-resistant state, which drives hyperandrogenism and anovulatory infertility. The metabolic action of metformin involves amelioration of insulin resistance, which helps to resolve hormonal and metabolic disturbances and increases ovulation, pregnancy, and live birth rates relative to placebo. A combination of metformin with clomifene citrate (another widely used treatment for PCOS) is more effective than either alone and is a useful option in women with clomifene-resistant PCOS. Combining metformin with letrozole (1st-line agent for ovulation induction in women with PCOS and no other infertility risk factors) is not more effective than letrozole alone. Continuing metformin to the end of the 1st trimester at an effective dose (e.g. 1000-2000 mg/day) may help to reduce the rate of miscarriages. Metformin also has an adjunctive role in women with PCOS receiving assisted reproduction technology (ART) using the long gonadotrophin-releasing hormone agonist protocol, where it appears to increase the pregnancy rate and to reduce the risk of ovarian hyperstimulation syndrome. There is no role for metformin in women receiving short ART protocols. Where a successful pregnancy is achieved, metformin is generally safe for the mother and neonate. Further research is needed to define with greater precision the optimal dosage and times to initiate and discontinue metformin in women with PCOS who achieve pregnancy.

Gastrointestinal adverse events of metformin treatment in patients with type 2 diabetes mellitus: a systematic review and meta-analysis with meta-regression of observational studies

INTRODUCTION

Metformin is the most prescribed medication for type 2 diabetes mellitus (T2DM); there is a well-established link with the elevated incidence of gastrointestinal (GI) adverse events (AE) limiting its administration or intensification.

OBJECTIVES

The objective of this systematic review and meta-analysis of observational studies was to evaluate the pooled incidence of GI AE related to metformin use in patients with T2DM.

MATERIALS AND METHODS

PUB MED/CINAHL/Web of Science/Scopus were searched from database inception until 29.07.2024 for observational studies in English describing the frequency of GI AE in patients with T2DM treated with metformin. Random-effects meta-analyses were used to derive effect sizes: event rates.

RESULTS

From 7019 publications, we identified 211 potentially eligible full-text articles. Ultimately, 21 observational studies were included in the meta-analysis. The prevalence of GI AE was as follows: diarrhea 6.9% (95% CI: 0.038-0.123), bloating 6,2% (95% CI: 0.020-0.177), abdominal pain 5,3% (95% CI: 0.003-0.529), vomiting 2.4% (95%: CI 0.007-0.075), constipation 1.1% (95%: CI 0.001-0.100). The incidence of bloating (coefficient -4.46; p < 0.001), diarrhea (coefficient -1.17; p = 0.0951) abdominal pain (coefficient -2.80; p = 0.001), constipation (coefficient -5.78; p = 0.0014) and vomiting (coefficient -2.47; p < 0.001) were lower for extended release (XR) metformin than metformin immediate release (IR) formulation.

CONCLUSIONS

This study highlights the prevalence of GI AE in patients receiving metformin, with a diarrhea predominance, followed by bloating, diarrhea, abdominal pain, constipation, and vomiting. The incidence is lower in patients administered with XR metformin.

TRIAL REGISTRATION

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42021289975 , identifier CRD42021289975.

Bioequivalence of Related GelShieldⓇ Sustained-release Formulations of Metformin: A Pooled Pharmacokinetic Analysis

PURPOSE

GlucophageⓇ (Merck Healthcare KGaA, Darmstadt, Germany) is the originator brand of metformin hydrochloride, an oral antidiabetic drug. Metformin is recommended in guidelines as first-line treatment of type 2 diabetes mellitus and increasingly in related insulin-resistant conditions, such as prediabetes and polycystic ovary syndrome. The GelShieldⓇ sustained-release formulation tablet of GlucophageⓇ has been improved from the historic version marketed in 2000. Bioequivalence has been demonstrated stepwise along this evolution; however, a head-to-head evaluation between the initial and the current version is missing. This analysis aims to close this gap and to determine bioequivalence between related originator GelShieldⓇ sustained-release formulations of metformin, GlucophageⓇ (GXR 500 mg), from Europe and the United States.

METHODS

Data from seven randomized crossover bioequivalence studies in 361 healthy participants of Asian and non-Asian ethnicity from Europe, the United States, and Asia were considered. All evaluated a single oral dose of 500 mg of the test and reference formulation in healthy male and female participants in fed and fasted state. Bioequivalence was evaluated by means of a combined bridging analysis of available data on the current round tablet from Europe (rGXR EU) and the historic oblong tablet from the United States (oGXR US) in healthy Asian and non-Asian participants under fed and fasting conditions. Bioequivalence between the two formulations was assessed statistically with a mixed effects model for AUC0-t, Cmax, and AUC0-inf.

FINDINGS

In all studies, bioequivalence between the respective test and reference formulations of GXR was shown. Statistical analysis of pooled pharmacokinetic data of 2 (primary pooling set) or 3 studies (secondary pooling set) demonstrated bioequivalence between rGXR EU and oGXR US via bridging with oGXR EU. The 90% CI for the geometric mean ratio of all pharmacokinetic parameters was within the bioequivalence range of 0.80 to 1.25. In the primary pooling set, geometric least squares mean ratios in the fed group ranged from 0.9931 (90% CI, 0.9151-1.0778) for AUC0-inf to 1.1344 (90% CI, 1.0711-1.2014) for Cmax; results in the fasted group were similar. The secondary pooling set, which added a study in Asians, confirmed these findings.

IMPLICATIONS

Bioequivalence was determined between sustained-release formulations of GlucophageⓇ from Europe and the United States under fasted and fed conditions in healthy men and women, including different ethnicities. The efficacy and safety of GlucophageⓇ XR can be claimed along the evolution from oGXR US, via oGXR EU to rGXR EU, and in several ethnicities and production sites.

Customized Hydrogel for Sustained Release of Highly Water-Soluble Drugs

Highly water-soluble drugs, due to the rapid diffusion in water, are difficult to be released sustainably. To address the issue, a hydrogel with a core-shell structure is designed for the release of highly water-soluble drugs. The core is used to load the drug and the shell is devoted to isolating the drug from the release medium, which can decrease the drug concentration gradient and the driving force of drug release. The core-shell structure prolongs the drug release time by extending the drug release pathway. Moreover, the core-shell hydrogel possesses high swelling properties to reside in the stomach. The results demonstrate that the customized hydrogel can prolong the release of the highly water-soluble drug (metformin hydrochloride) for more than 50 h and alleviate the burst release of the drug.

Budget Impact Analysis of Metformin Sustained Release for the Treatment of Type 2 Diabetes in The Netherlands

BACKGROUND

Adverse drug reactions and medication nonadherence are well-known causes of sub-optimal disease control and worsened disease outcomes in patients who are treated for type 2 diabetes. Metformin sustained release (SR) might reduce these adverse events and improve medication adherence via a simplified treatment regimen for metformin immediate release (IR)-intolerant patients.

OBJECTIVES

The aim of this study is to estimate the budget impact of metformin SR for the treatment of type 2 diabetes in the Netherlands, compared to the current standard of care (SoC) with metformin IR.

METHODS

A budget impact model was built to represent the course of the disease and treatment pathway of type 2 diabetes patients eligible for metformin SR from a healthcare payer's perspective. Patients were considered eligible if they used less than 2000 mg metformin IR per day, but suffered from adverse events that might lead to therapy discontinuation, and if they were newly diagnosed with type 2 diabetes. The costs of type 2 diabetes treatment and related complications over a time horizon of 3 years were calculated. Univariate sensitivity analyses were conducted to show which parameters have the biggest influence on the budget impact.

RESULTS

The budget impact analysis showed cost-savings of - €1,962,335 over a period of 3 years through implementation of metformin SR as an alternative to SoC with metformin IR. Savings were mostly driven by the delay of other, more expensive type 2 diabetes treatments, such as insulin. In sensitivity analyses, medication adherence and persistence appeared to have the biggest influence on the budget impact.

CONCLUSION

Metformin SR could potentially be a cost-saving alternative to metformin IR for the treatment of type 2 diabetes in the Netherlands, especially in patients experiencing adverse events with metformin IR. However, more research is needed to better predict the effect of using once-daily metformin, compared to multiple dosages, on medication adherence and persistence and to evaluate whether metformin SR really decreases the amount of adverse events.

Sixty Years of Drug Discovery for Type 2 Diabetes: Where Are We Now?

Today, excluding insulin, there are eight classes of anti-diabetic medicines that have been added to the pharmacy since the introduction of metformin in the mid-1950s; the sulfonylureas, biguanides, thiazolidinediones, α-glucosidase inhibitors, meglitinides, incretins, and sodium glucose transport 2 inhibitors. Does the fact that metformin is still first-line treatment suggest that our drug discovery efforts over the past 60 years have not been good enough? Or does it suggest that diabetes is such a complex disorder that no single treatment, other than gastric bypass surgery, can affect true normalization of not only blood sugar but also the underlying pathologies? Our understanding of the disease has most definitely improved which may bring hope for the future in terms of science, but for it to be beneficial, this science has to be translated into better drug treatments for the disease. In this review, I have examined the eight classes of anti-diabetes drugs from a drug discovery perspective.

Toxicity of Metformin and Hypoglycemic Therapies

Metformin along with other antidiabetic medications provide benefit to patients in the treatment of type 2 diabetes mellitus, but caution is advised in certain scenarios to avoid toxicity in kidney disease. Renal dosing, monitoring of kidney function, and evaluating the risk of developing serious side effects are warranted with some agents. The available literature with regard to incidence of adverse events and toxicity of hypoglycemic therapies is reviewed.

Metformin: historical overview

Metformin (dimethylbiguanide) has become the preferred first-line oral blood glucose-lowering agent to manage type 2 diabetes. Its history is linked to Galega officinalis (also known as goat's rue), a traditional herbal medicine in Europe, found to be rich in guanidine, which, in 1918, was shown to lower blood glucose. Guanidine derivatives, including metformin, were synthesised and some (not metformin) were used to treat diabetes in the 1920s and 1930s but were discontinued due to toxicity and the increased availability of insulin. Metformin was rediscovered in the search for antimalarial agents in the 1940s and, during clinical tests, proved useful to treat influenza when it sometimes lowered blood glucose. This property was pursued by the French physician Jean Sterne, who first reported the use of metformin to treat diabetes in 1957. However, metformin received limited attention as it was less potent than other glucose-lowering biguanides (phenformin and buformin), which were generally discontinued in the late 1970s due to high risk of lactic acidosis. Metformin's future was precarious, its reputation tarnished by association with other biguanides despite evident differences. The ability of metformin to counter insulin resistance and address adult-onset hyperglycaemia without weight gain or increased risk of hypoglycaemia gradually gathered credence in Europe, and after intensive scrutiny metformin was introduced into the USA in 1995. Long-term cardiovascular benefits of metformin were identified by the UK Prospective Diabetes Study (UKPDS) in 1998, providing a new rationale to adopt metformin as initial therapy to manage hyperglycaemia in type 2 diabetes. Sixty years after its introduction in diabetes treatment, metformin has become the most prescribed glucose-lowering medicine worldwide with the potential for further therapeutic applications.

Understanding and overcoming metformin gastrointestinal intolerance

Metformin is the most widely prescribed drug for patients with type 2 diabetes mellitus and the first-line pharmacological option as supported by multiple international guidelines, yet a rather large proportion of patients cannot tolerate metformin in adequate amounts because of its associated gastrointestinal (GI) adverse events (AEs). GI AEs typically encountered with metformin therapy include diarrhoea, nausea, flatulence, indigestion, vomiting and abdominal discomfort, with diarrhoea and nausea being the most common. Although starting at a low dose and titrating slowly may help prevent some GI AEs associated with metformin, some patients are unable to tolerate metformin at all and it may also be difficult to convince patients to start metformin again after a bout of GI AEs. Despite this clinical importance, the underlying mechanisms of the GI intolerance associated with metformin are poorly known. In the present review, we discuss: the epidemiology of metformin-associated GI intolerance and its underlying mechanisms; genotype variability and associated factors affecting metformin GI intolerance, such as comorbidities, co-medications and bariatric surgery; clinical consequences and therapeutic strategies to overcome metformin GI intolerance. These strategies include appropriate titration of immediate-release metformin, use of extended-release metformin, the promise of delayed-release metformin and gut microbiome modulators, as well as alternative pharmacological therapies when metformin cannot be tolerated at all. Given the available data, all efforts should be made to maintain metformin before considering a shift to another drug therapy.

Metformin-like antidiabetic, cardio-protective and non-glycemic effects of naringenin: Molecular and pharmacological insights

Metformin is a widely used drug for the treatment of type 2 diabetes (T2D). Its blood glucose-lowering effects are initially due to inhibition of hepatic glucose production and increased peripheral glucose utilization. Metformin has also been shown to have several beneficial effects on cardiovascular risk factors and it is the only oral antihyperglycaemic agent thus far associated with decreased macrovascular complications in patients with diabetes. Adenosine Monophosphate Activated-Protein Kinase (AMPK) is a major cellular regulator of lipid and glucose metabolism. Recent evidence shows that pharmacological activation of AMPK improves blood glucose homeostasis, lipid profiles, blood pressure and insulin-resistance making it a novel therapeutic target in the treatment of T2D. Naringenin a flavonoid found in high concentrations as its glycone naringin in citrus fruits, has been reported to have antioxidant, antiatherogenic, anti- dyslipidemic and anti-diabetic effects. It has been shown that naringenin exerts its anti-diabetic effects by inhibition of gluconeogenesis through upregulations of AMPK hence metformin-like effects. Naringin has further been shown to have non-glycemic affects like metformin that mitigate inflammation and cell proliferation. This review evaluates the potential of naringenin as anti-diabetic, anti-dyslipidemic anti-inflammatory and antineoplastic agent similar to metformin and proposes its further development for therapeutic use in clinical practice.

Tolerability of prolonged-release metformin (Glucophage® SR) in individuals intolerant to standard metformin — results from four UK centres

Advances in drug formulation have improved the tolerability of many commonly used agents. Metformin is recommended as initial drug therapy for type 2 diabetes and has proven long-term efficacy and safety. However, gastrointestinal (GI) side-effects of standard, immediate-release (IR) metformin often reduce medication adherence and limit dose titration. A prolonged-release metformin formulation may improve tolerability over its IR counterpart. We report the results of two prospective and two retrospective clinic-based evaluations of the tolerability of metformin in a total of 95 patients intolerant to standard IR metformin assessed over three to six months following a switch from IR to prolonged-release metformin (Glucophage® SR). Between 62% and 100% of patients from the centres tolerated the prolonged-release formulation. Glycaemia following the switch was improved or unchanged. Prolonged-release metformin represents a useful option for patients intolerant of standard IR metformin due to GI side-effects. This improved tolerance of prolonged-release metformin may improve medication adherence and thereby enhance treatment outcomes.

Effects of body mass index or dosage on gastrointestinal disorders associated with extended-release metformin in type 2 diabetes: Sub-analysis of a Phase IV open-label trial in Chinese patients

AIM

To determine whether gastrointestinal (GI) tolerability of metformin monotherapy varies according to baseline BMI or at doses >1500mg/day in patients newly diagnosed with type 2 diabetes.

METHODS

We performed a sub-analysis of the safety population from a prospective, multicenter, Phase IV open-label study in which 371 Chinese patients with type 2 diabetes received extended-release metformin monotherapy for 16 weeks. The incidence, severity and duration of GI adverse events (AEs) were compared between normal-weight (BMI<25kg/m(2), n=155) and overweight/obese (BMI≥25kg/m(2), n=216) patients. The primary objective was to determine whether baseline BMI affect the incidence, severity and duration of GI AEs, using Fisher's exact test and Student's t-test. Secondary objectives were to compare these factors according to final metformin dose (≤1500mg/day versus 2000mg/day).

RESULTS

The proportion of patients who reported ≥1 GI AE did not differ significantly between BMI groups (25.2% of the normal-weight group versus 21.3% of the overweight/obese group; p=0.3840). Patients who reported GI AEs in the two BMI groups experienced similar GI AE severity (p=0.5410), mean duration (p=0.3572) and duration distribution (p=0.1347). There was no significant difference in GI AE severity and duration between metformin dosage groups (≤1500mg/day versus 2000mg/day).

CONCLUSIONS

Newly-diagnosed Chinese type 2 diabetes patients of normal weight are no more likely than overweight/obese patients to suffer from increased incidence rates, severity or duration of GI AEs when treated with first-line extended-release metformin monotherapy. Doses of 2000mg/day did not increase the severity or duration of GI AEs.

Metformin and the gastrointestinal tract

Metformin is an effective agent with a good safety profile that is widely used as a first-line treatment for type 2 diabetes, yet its mechanisms of action and variability in terms of efficacy and side effects remain poorly understood. Although the liver is recognised as a major site of metformin pharmacodynamics, recent evidence also implicates the gut as an important site of action. Metformin has a number of actions within the gut. It increases intestinal glucose uptake and lactate production, increases GLP-1 concentrations and the bile acid pool within the intestine, and alters the microbiome. A novel delayed-release preparation of metformin has recently been shown to improve glycaemic control to a similar extent to immediate-release metformin, but with less systemic exposure. We believe that metformin response and tolerance is intrinsically linked with the gut. This review examines the passage of metformin through the gut, and how this can affect the efficacy of metformin treatment in the individual, and contribute to the side effects associated with metformin intolerance.

Dipeptidyl Peptidase-4 Inhibitors in Diverse Patient Populations With Type 2 Diabetes

PURPOSE

The purpose of this review is to discuss the clinical evidence for dipeptidyl peptidase-4 (DPP-4) inhibitors and to better define their use in treating type 2 diabetes mellitus (T2DM), including in special populations, such as the elderly. DPP-4 inhibitors are incretin-based therapies that can be used as monotherapy or in combination with other antidiabetes medications to treat T2DM. As monotherapy, DPP-4 inhibitors have demonstrated a modest and comparable glycated hemoglobin-lowering effect. As initial dual therapy with other antidiabetes agents, DPP-4 inhibitors significantly improved glycated hemoglobin when compared with monotherapy arms. Similarly, in triple combinations, DPP-4 inhibitors consistently provided additive glycemic benefits. In patients who were continuing insulin, glycemic parameters were improved with the addition of a DPP-4 inhibitor, and they required less insulin uptitration. In clinical trials, the overall occurrence of adverse events was similar between DPP-4 inhibitor groups and controls, and a low occurrence of hypoglycemia was observed, except when used in combination with a sulfonylurea. A neutral effect on weight was maintained, even in combination with insulin. Similar to outcomes observed in younger patients, DPP-4 inhibitors significantly improved glycemic efficacy in older patients, without increasing the risk for hypoglycemia. Efficacy and safety in patients with renal insufficiency are also documented.

CONCLUSION

DPP-4 inhibitors are therapeutically beneficial for a diverse population of patients with T2DM, including elderly patients, based on demonstrated efficacy, tolerability, and a low risk for hypoglycemia.

Adding Saxagliptin to Metformin Extended Release (XR) or Uptitration of Metformin XR: Efficacy on Daily Glucose Measures

INTRODUCTION

Saxagliptin added to metformin extended release (XR) and uptitrated metformin XR were evaluated for their impact on daily glucose measurements and their tolerability in patients with type 2 diabetes mellitus (T2DM) inadequately controlled with metformin monotherapy.

METHODS

Patients aged 18-78 years on metformin 850-1,500 mg with glycated hemoglobin (HbA1c) 7.5-11.5% at screening were eligible for this double-blind, active-controlled study. Patients were stabilized on metformin XR 1,500 mg before randomization. Patients with HbA1c 7-11% and fasting plasma glucose (FPG) ≥126 mg/dL after a 4- 8-week lead-in period were randomly assigned to saxagliptin 5 mg + metformin XR 1,500 mg or metformin XR 500 mg + metformin XR 1,500 mg (uptitrated metformin XR). The primary end point was change from baseline to week 4 in 24-h mean weighted glucose (MWG). Secondary end points were changes from baseline to week 4 in 2-h postprandial glucose (PPG) and FPG.

RESULTS

At week 4, the adjusted mean ± SE change from baseline in 24-h MWG was -19.0 ± 5.7 mg/dL (95% CI -30.3 to -7.6) for saxagliptin + metformin XR and -8.2 ± 6.0 mg/dL (95% CI -20.0 to 3.7) for uptitrated metformin XR. Mean changes from baseline in 2-h PPG and FPG were numerically greater with saxagliptin + metformin XR versus uptitrated metformin XR. The incidence of adverse events was lower with saxagliptin + metformin XR (17.4%) versus uptitrated metformin XR (31.9%) mainly due to differences in gastrointestinal adverse event incidence (2.2% vs 10.6%, respectively). There were no reports of confirmed hypoglycemia in either group.

CONCLUSION

In this 4-week study in patients with T2DM inadequately controlled with metformin monotherapy, saxagliptin added to metformin XR demonstrated a trend for improvement in measures of daily glycemic control, with fewer gastrointestinal adverse events, compared with uptitrated metformin.

Safety, tolerability, and efficacy of metformin extended-release oral antidiabetic therapy in patients with type 2 diabetes: an observational trial in Asia

BACKGROUND

The aim of the present prospective observational study was to assess the tolerability and antihyperglycemic efficacy of metformin extended-release (MXR) in the routine treatment of patients with type 2 diabetes mellitus (T2DM) from six Asian countries.

METHODS

Data from 3556 patients treated with once-daily MXR for 12 weeks, or until discontinuation, were analyzed.

RESULTS

Treatment with MXR was well tolerated, with 97.4% of patients completing 12 weeks of treatment. Only 3.3% of patients experienced one or more gastrointestinal (GI) side-effects and only 0.7% of patients discontinued for this reason (primary endpoint). The incidence of GI side-effects and related discontinuations appeared to be considerably lower during short-term MXR therapy than during previous treatment (mean 2.71 years' duration), most commonly with immediate-release metformin. A 12-week course of MXR therapy also reduced HbA1c and fasting glucose levels from baseline.

CONCLUSIONS

The present study provides new insights into the incidence of GI side-effects with MXR in Asian patients with T2DM and on the tolerability of MXR in non-Caucasian populations. Specifically, these data indicate that once-daily MXR not only improves measures of glycemic control in Asian patients with T2DM, but also has a favorable GI tolerability profile that may help promote enhanced adherence to oral antidiabetic therapy.

Combination treatment with ipragliflozin and metformin: a randomized, double-blind, placebo-controlled study in patients with type 2 diabetes mellitus

BACKGROUND

Ipragliflozin (ASP1941) is a selective sodium glucose cotransporter 2 inhibitor in clinical development for the treatment of patients with type 2 diabetes mellitus (T2DM).

OBJECTIVES

The primary objective was to evaluate the safety profile and tolerability of ipragliflozin as a glucose-lowering agent in combination with stable metformin therapy in patients with T2DM. A secondary objective was to evaluate the effect of ipragliflozin on the pharmacokinetic (PK) properties of metformin.

METHODS

Thirty-six patients with T2DM stable on metformin therapy (850, 1000, or 1500 mg bid) were randomized in a double-blind manner to receive ipragliflozin (300 mg qd; n = 18) or matching placebo (n = 18) for 14 days. Safety profiles, including monitoring of hypoglycemic events, treatment-emergent adverse events (TEAEs), laboratory measurements, and vital signs were assessed throughout the study. The PK properties of metformin and ipragliflozin were determined in plasma. The geometric mean ratio and its 90% CI for the maximum plasma concentration and AUC(0-10) were calculated for metformin + ipragliflozin (day 14) versus metformin alone (day -1). Pharmacodynamic properties were assessed by measurement of urinary glucose excretion over 24 hours (UGE(0-24)).

RESULTS

All the TEAEs, except 1, were mild. Fifteen TEAEs were observed in the ipragliflozin group (7 of 18 patients [38.9%]), and 19 TEAEs were observed in the placebo group in (8 of 18 patients [44.4%]). Treatment-related TEAEs were reported by 3 of 18 patients (16.7%) receiving metformin + ipragliflozin and by 5 of 18 patients (27.8%) receiving metformin + placebo. No hypoglycemic events (blood glucose level <54 mg/L [to convert to millimoles per liter, multiply by 0.0555]) were observed. The geometric mean ratios for C(max) and AUC(0-10) of metformin + ipragliflozin versus metformin alone were 1.11 (90% CI, 1.03-1.19) and 1.18 (90% CI, 1.08-1.28), respectively. After ipragliflozin treatment, UGE(0-24) on day 14 (74.9 g) was significantly higher than that in the placebo group (3.6 g) and at baseline (3.3 g).

CONCLUSIONS

Combination treatment for 14 days with ipragliflozin and metformin was well tolerated in patients withT2DM without hypoglycemia. The addition of ipragliflozin (300 mg qd) to metformin therapy did not result in a clinically relevant change in the PK properties of metformin. ClinicalTrials.gov identifier: NCT01302145.

Adding saxagliptin to extended-release metformin vs. uptitrating metformin dosage

AIM

To investigate whether patients taking metformin for type 2 diabetes mellitus (T2DM) have improved glycaemic control without compromising tolerability by adding an agent with a complementary mechanism of action vs. uptitrating metformin.

METHODS

Adults with T2DM and glycated haemoglobin (HbA1c) between 7.0 and 10.5% receiving metformin extended release (XR) 1500 mg/day for ≥8 weeks were randomized to receive saxagliptin 5 mg added to metformin XR 1500 mg (n = 138) or metformin XR uptitrated to 2000 mg/day (n = 144). Endpoints were change from baseline to week 18 in HbA1c (primary), 120-min postprandial glucose (PPG), fasting plasma glucose (FPG) and the proportion of patients achieving HbA1c <7%.

RESULTS

At week 18, the adjusted mean reduction from baseline HbA1c was -0.88% for saxagliptin + metformin XR and -0.35% for uptitrated metformin XR (difference, -0.52%; p < 0.0001). For 120-min PPG and FPG, differences in adjusted mean change from baseline between saxagliptin + metformin XR and uptitrated metformin XR were -1.3 mmol/l (-23.32 mg/dl) (p = 0.0013) and -0.73 mmol/l (-13.18 mg/dl) (p = 0.0030), respectively. More patients achieved HbA1c <7.0% with saxagliptin + metformin XR than with uptitrated metformin XR (37.2 vs. 26.1%; p = 0.0459). The proportions of patients experiencing any adverse events (AEs) were generally similar between groups; neither group showed any notable difference in hypoglycaemia or gastrointestinal AEs.

CONCLUSION

Adding saxagliptin to metformin XR provided superior glycaemic control compared with uptitrating metformin XR without the emergence of additional safety concerns.

Clinical pharmacokinetics of metformin

Metformin is widely used for the treatment of type 2 diabetes mellitus. It is a biguanide developed from galegine, a guanidine derivative found in Galega officinalis (French lilac). Chemically, it is a hydrophilic base which exists at physiological pH as the cationic species (>99.9%). Consequently, its passive diffusion through cell membranes should be very limited. The mean ± SD fractional oral bioavailability (F) of metformin is 55 ± 16%. It is absorbed predominately from the small intestine. Metformin is excreted unchanged in urine. The elimination half-life (t(&frac12;)) of metformin during multiple dosages in patients with good renal function is approximately 5 hours. From published data on the pharmacokinetics of metformin, the population mean of its clearances were calculated. The population mean renal clearance (CL(R)) and apparent total clearance after oral administration (CL/F) of metformin were estimated to be 510 ± 130 mL/min and 1140 ± 330 mL/min, respectively, in healthy subjects and diabetic patients with good renal function. Over a range of renal function, the population mean values of CL(R) and CL/F of metformin are 4.3 ± 1.5 and 10.7 ± 3.5 times as great, respectively, as the clearance of creatinine (CL(CR)). As the CL(R) and CL/F decrease approximately in proportion to CL(CR), the dosage of metformin should be reduced in patients with renal impairment in proportion to the reduced CL(CR). The oral absorption, hepatic uptake and renal excretion of metformin are mediated very largely by organic cation transporters (OCTs). An intron variant of OCT1 (single nucleotide polymorphism [SNP] rs622342) has been associated with a decreased effect on blood glucose in heterozygotes and a lack of effect of metformin on plasma glucose in homozygotes. An intron variant of multidrug and toxin extrusion transporter [MATE1] (G>A, SNP rs2289669) has also been associated with a small increase in antihyperglycaemic effect of metformin. Overall, the effect of structural variants of OCTs and other cation transporters on the pharmacokinetics of metformin appears small and the subsequent effects on clinical response are also limited. However, intersubject differences in the levels of expression of OCT1 and OCT3 in the liver are very large and may contribute more to the variations in the hepatic uptake and clinical effect of metformin. Lactic acidosis is the feared adverse effect of the biguanide drugs but its incidence is very low in patients treated with metformin. We suggest that the mean plasma concentrations of metformin over a dosage interval be maintained below 2.5 mg/L in order to minimize the development of this adverse effect.

Assessment of efficacy and tolerability of once-daily extended release metformin in patients with type 2 diabetes mellitus

AIMS

To determine prospectively the efficacy, tolerability and patient satisfaction of an extended release formulation of metformin (metformin XR) in hospital based outpatients with type 2 diabetes mellitus currently treated with standard metformin.

METHODS

Patients on immediate release standard metformin either alone or combined with other oral agents were switched to extended release metformin XR 500 mg tablets and titrated to a maximum dose of 2000 mg/day Measurements to include glucose and lipid control, blood pressure, body weight, waist circumference, C-reactive protein, adverse events and patient satisfaction were recorded at baseline, three and six months.

RESULTS

Complete data were obtained for 35 of the 61 patients enrolled to the study. At three and six months no changes were reported for any of the cardiovascular risk factors except for lipids where there was a modest rise in plasma triglycerides. These effects were achieved with a reduced dose of metformin XR compared to pre-study dosing with standard metformin (1500 mg +/- 402 vs 1861 +/- 711 p = 0.004). A total of 77% of patients were free of gastrointestinal side effects and 83% of patients stated a preference for metformin XR at the end of the study. Ghost tablets were reported in the faeces by the majority of the patients (54.1%).

CONCLUSIONS

Patients switched to extended release metformin XR derived the same clinical and metabolic benefits as for standard metformin but with reduced dosage, fewer gastrointestinal side effects and a greater sense of well being and satisfaction on medication.

Metformin therapy and clinical uses

Metformin is now established as a first-line antidiabetic therapy for the management of type 2 diabetes. Its early use in treatment algorithms is supported by lack of weight gain, low risk of hypoglycaemia and its mode of action to counter insulin resistance. The drug's anti-atherosclerotic and cardioprotective effects have recently been confirmed in prospective and retrospective studies, and appear to reflect a collection of glucose-independent effects on the vascular endothelium, suppressant effects on glycation, oxidative stress and formation of adhesion molecules, stimulation of fibrinolysis and favourable effects on the lipid profile. Although avoidance of troublesome gastrointestinal tolerability issues requires careful dose titration, the risk of serious adverse events is considered low provided that contra-indications (especially with respect to renal function) are observed. As many of its actions go beyond glucose lowering, emerging evidence indicates potential benefits in other insulin-resistant states and possibly tumour suppression.

Role of metformin in the initiation of pharmacotherapy for type 2 diabetes: an Asian-Pacific perspective

Increases in the prevalence of type 2 diabetes of 30-60% will occur in many Asian-Pacific countries by 2025, driven by urbanisation, sedentary habits and energy-rich diets. Obesity, insulin resistance, metabolic syndrome and diabetes are closely interrelated. Optimal control of diabetes and associated risk factors has reduced the risk of diabetes-related complications. In the UK Prospective Diabetes Study (UKPDS), metformin reduced the risk of macrovascular complications and retrospective analyses have confirmed the efficacy of metformin in improving clinical outcomes in type 2 diabetic patients with a history of cardiovascular disease. This growing body of evidence has led to the recommendation of metformin as optimum initial pharmacotherapy in overweight type 2 diabetic patients. Obesity is less prevalent in the Asian-Pacific population than in Caucasian populations. Nevertheless, metformin has multiple beneficial metabolic effects, which provide sufficient rationale for it to be recommended as the initial oral anti-diabetic pharmacotherapy, alone or in combination, irrespective of body mass index. This recommendation is consistent with global guidelines and regional recommendations for the Asian-Pacific region from the International Diabetes Federation. These recommendations can serve as templates for development of local guidelines for Asian people with diabetes, given the ethnic and cultural diversity within the region.