Introducing estimated glomerular filtration rate (eGFR) into clinical practice in the UK: implications for the use of metformin

Monitoring Patients on Metformin: Recent Changes and Rationales

Objective: The Food and Drug Administration recently updated metformin prescribing recommendations for patients with diabetes and renal disease. The American Diabetes Association as well as the American Association of Clinical Endocrinologists and American Clinical Endocrinologists also recommend periodic monitoring of vitamin B12 levels for patients using metformin. A review of the literature was conducted to assess data to evaluate the recent updates to metformin usage and provide rationales for these recommendations. Data Sources: PubMed MESH terms "Diabetes Mellitus, Type 2" and "Renal Insufficiency, Chronic" and "Metformin" were searched with an English limitation from 1990 to May 2017. A MEDLINE search was conducted using the terms "metformin" and "renal disease" from 1990 to May 2017. A PubMed search was conducted using the MESH terms "vitamin b12 deficiency" and "metformin" from 1970 to May 2017. A MEDLINE search was conducted using terms "metformin" and "vitamin B12 deficiency" with an English limitation from 1970 to May 2017. Study Selection and Data Extraction: Retrospective and prospective clinical trials, meta-analyses, and systematic reviews were considered for inclusion. Citations from identified articles were also reviewed for inclusion. Data Synthesis: The incidence of metformin-associated lactic acidosis is minimal. Data indicate metformin-treated patients with an estimated glomerular filtration rate above 30 mL/min/1.73 m2 have a reduction in mortality. Additionally, data suggest metformin may lead to vitamin B12 deficiency. Conclusion: Data support recommendations for metformin use in patients with diabetes and renal insufficiency with an estimated glomerular filtration rate above 30 mL/min/1.73 m2. Data also suggest that baseline and periodic testing of vitamin B12 levels are warranted and supported by clinical guidelines due to the risk of vitamin B12 deficiency in metformin-treated patients.

Risk of acute kidney injury and survival in patients treated with Metformin: an observational cohort study

BACKGROUND

Whether metformin precipitates lactic acidosis in patients with chronic kidney disease (CKD) remains under debate. We examined whether metformin use was associated with an increased risk of acute kidney injury (AKI) as a proxy for lactic acidosis and whether survival among those with AKI varied by metformin exposure.

METHODS

All individuals with type 2 diabetes and available prescribing data between 2004 and 2013 in Tayside, Scotland were included. The electronic health record for diabetes which includes issued prescriptions was linked to laboratory biochemistry, hospital admission, death register and Scottish Renal Registry data. AKI events were defined using the Kidney Disease Improving Global Outcomes criteria with a rise in serum creatinine of at least  26.5 μmol/l or a rise of greater than 150% from baseline for all hospital admissions. Cox Regression Analyses were used to examine whether person-time periods in which current metformin exposure occurred were associated with an increased rate of first AKI compared to unexposed periods. Cox regression was also used to compare 28 day survival rates following first AKI events in those exposed to metformin versus those not exposed.

RESULTS

Twenty-five thousand one-hundred fourty-eight patients were included with a total person-time of 126,904 person years. 4944 (19.7%) people had at least one episode of AKI during the study period. There were 32.4 cases of first AKI/1000pyrs in current metformin exposed person-time periods compared to 44.9 cases/1000pyrs in unexposed periods. After adjustment for age, sex, diabetes duration, calendar time, number of diabetes drugs and baseline renal function, current metformin use was not associated with AKI incidence, HR 0.94 (95% CI 0.87, 1.02, p = 0.15). Among those with incident AKI, being on metformin at admission was associated with a higher rate of survival at 28 days (HR 0.81, 95% CI 0.69, 0.94, p = 0.006) even after adjustment for age, sex, pre-admission eGFR, HbA1c and diabetes duration.

CONCLUSIONS

Contrary to common perceptions, we found no evidence that metformin increases incidence of AKI and was associated with higher 28 day survival following incident AKI.

Potential Impact of Prescribing Metformin According to eGFR Rather Than Serum Creatinine

OBJECTIVE

Many societies recommend using estimated glomerular filtration rate (eGFR) rather than serum creatinine (sCr) to determine metformin eligibility. We examined the potential impact of these recommendations on metformin eligibility among U.S. adults.

RESEARCH DESIGN AND METHODS

Metformin eligibility was assessed among 3,902 adults with diabetes who participated in the 1999-2010 National Health and Nutrition Examination Surveys and reported routine access to health care, using conventional sCr thresholds (eligible if <1.4 mg/dL for women and <1.5 mg/dL for men) and eGFR categories: likely safe, ≥45 mL/min/1.73 m(2); contraindicated, <30 mL/min/1.73 m(2); and indeterminate, 30-44 mL/min/1.73 m(2)). Different eGFR equations were used: four-variable MDRD, Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) creatinine (CKD-EPIcr), and CKD-EPI cystatin C, as well as Cockcroft-Gault (CG) to estimate creatinine clearance (CrCl). Diabetes was defined by self-report or A1C ≥6.5% (48 mmol/mol). We used logistic regression to identify populations for whom metformin was likely safe adjusted for age, race/ethnicity, and sex. Results were weighted to the U.S. adult population.

RESULTS

Among adults with sCr above conventional cutoffs, MDRD eGFR ≥45 mL/min/1.73 m(2) was most common among men (adjusted odds ratio [aOR] 33.3 [95% CI 7.4-151.5] vs. women) and non-Hispanic Blacks (aOR vs. whites 14.8 [4.27-51.7]). No individuals with sCr below conventional cutoffs had an MDRD eGFR <30 mL/min/1.73 m(2). All estimating equations expanded the population of individuals for whom metformin is likely safe, ranging from 86,900 (CKD-EPIcr) to 834,800 (CG). All equations identified larger populations with eGFR 30-44 mL/min/1.73 m(2), for whom metformin safety is indeterminate, ranging from 784,700 (CKD-EPIcr) to 1,636,000 (CG).

CONCLUSIONS

The use of eGFR or CrCl to determine metformin eligibility instead of sCr can expand the adult population with diabetes for whom metformin is likely safe, particularly among non-Hispanic blacks and men.

Metformin initiation and renal impairment: a cohort study in Denmark and the UK

OBJECTIVES

To estimate prevalence of renal impairment, rate of decline in kidney function and changes in metformin use after decline in kidney function, in metformin initiators.

DESIGN, SETTING AND PARTICIPANTS

We conducted this 2-country cohort study using routine data from northern Denmark and the UK during 2000-2011. We included metformin initiators among patients aged ≥30 years with medically treated diabetes.

MAIN OUTCOME MEASURES

We described patients' demographics, comorbidity, co-medications and their estimated glomerular filtration rates (eGFR). Furthermore, we described the patients' characteristics according to eGFR level. Finally, we examined the rate of any decline in eGFR and changes in metformin use within 90 days after first decline in eGFR during follow-up.

RESULTS

We included 124,720 metformin initiators in the 2 countries. Prevalence of eGFR <60 mL/min/1.73 m(2) among metformin initiators was 9.0% in Denmark and 25.2% in the UK. In contrast, prevalence of eGFR values <30 mL/min/1.73 m(2) among metformin initiators was 0.3% in Denmark and 0.4% in the UK. Patients with renal impairment were older and more likely to have received cardiovascular drugs. Incidence rate of decline in renal function was 4.92 per 100 person-years (95% CI 4.76 to 5.09) in Denmark and 7.48 per 100 person-years (95% CI 7.39 to 7.57) in the UK. The proportion of patients continuing metformin use, even after a first decline brought the eGFR below 30 mL/min/1.73 m(2), was 44% in Denmark and 62% in the UK. There was no clinically significant dose reduction with decreasing baseline eGFR level discernible from the data.

CONCLUSIONS

Mild to moderate renal impairment was common among metformin initiators, while severe renal impairment was uncommon. Patients with severe renal impairment frequently continued receiving/redeeming metformin prescriptions even 90 days after eGFR decline.

Metformin in patients with type 2 diabetes and kidney disease: a systematic review

IMPORTANCE

Metformin is widely viewed as the best initial pharmacological option to lower glucose concentrations in patients with type 2 diabetes mellitus. However, the drug is contraindicated in many individuals with impaired kidney function because of concerns of lactic acidosis.

OBJECTIVE

To assess the risk of lactic acidosis associated with metformin use in individuals with impaired kidney function.

EVIDENCE ACQUISITION

In July 2014, we searched the MEDLINE and Cochrane databases for English-language articles pertaining to metformin, kidney disease, and lactic acidosis in humans between 1950 and June 2014. We excluded reviews, letters, editorials, case reports, small case series, and manuscripts that did not directly pertain to the topic area or that met other exclusion criteria. Of an original 818 articles, 65 were included in this review, including pharmacokinetic/metabolic studies, large case series, retrospective studies, meta-analyses, and a clinical trial.

RESULTS

Although metformin is renally cleared, drug levels generally remain within the therapeutic range and lactate concentrations are not substantially increased when used in patients with mild to moderate chronic kidney disease (estimated glomerular filtration rates, 30-60 mL/min per 1.73 m2). The overall incidence of lactic acidosis in metformin users varies across studies from approximately 3 per 100,000 person-years to 10 per 100,000 person-years and is generally indistinguishable from the background rate in the overall population with diabetes. Data suggesting an increased risk of lactic acidosis in metformin-treated patients with chronic kidney disease are limited, and no randomized controlled trials have been conducted to test the safety of metformin in patients with significantly impaired kidney function. Population-based studies demonstrate that metformin may be prescribed counter to prevailing guidelines suggesting a renal risk in up to 1 in 4 patients with type 2 diabetes mellitus--use which, in most reports, has not been associated with increased rates of lactic acidosis. Observational studies suggest a potential benefit from metformin on macrovascular outcomes, even in patients with prevalent renal contraindications for its use.

CONCLUSIONS AND RELEVANCE

Available evidence supports cautious expansion of metformin use in patients with mild to moderate chronic kidney disease, as defined by estimated glomerular filtration rate, with appropriate dosage reductions and careful follow-up of kidney function.

Treating the elderly diabetic patient: special considerations

The prevalence of diabetes is rising in the >65 year-old group. The challenge of defining the goals of therapy arises from the heterogeneity of the aging process and the sparse clinical data in this patient population. In light of these challenges, the clinician should be aware of the pitfalls of caring for the older diabetic patient and prioritize an individualized treatment plan to ensure an optimal glycemic control, without placing the patient at unnecessary risk. We present a review of the current guidelines and literature that deal specifically with the treatment of the older diabetic patient in order to establish the principles of treatment in this age group and help the clinician make decisions regarding the care of these patients.

Use of metformin in diseases of aging

Metformin is the most commonly prescribed medication for type 2 diabetes (T2DM) in the world. It has primacy in the treatment of this disease because of its safety record and also because of evidence for reduction in the risk of cardiovascular events. Evidence has accumulated indicating that metformin is safe in people with stage 3 chronic kidney disease (CKD-3). It is estimated that roughly one-quarter of people with CKD-3 and T2DM in the United States (well over 1 million) are ineligible for metformin treatment because of elevated serum creatinine levels. This could be overcome if a scheme, perhaps based on pharmacokinetic studies, could be developed to prescribe reduced doses of metformin in these individuals. There is also substantial evidence from epidemiologic studies to indicate that metformin may not only be safe, but may actually benefit people with heart failure (HF). Prospective, randomized trials of the use of metformin in HF are needed to investigate this possibility.

Metformin therapy and kidney disease: a review of guidelines and proposals for metformin withdrawal around the world

OBJECTIVE

We compared and contrasted guidelines on metformin treatment in patients with chronic kidney disease (CKD) around the world, with the aim of helping physicians to refine their analysis of the available evidence before deciding whether to continue or withdraw this drug.

METHODS

We performed a systematic research for metformin contraindications in: (i) official documents from the world's 20 most populated countries and the 20 most scientifically productive countries in the field of diabetology and (ii) publications referenced in electronic databases from 1990 onwards.

RESULTS

We identified three international guidelines, 31 national guidelines, and 20 proposals in the scientific literature. The criteria for metformin withdrawal were (i) mainly qualitative in the most populated countries; (ii) mainly quantitative in the most scientifically productive countries (with, in all cases, a suggested threshold for withdrawing metformin); and (iii) quantitative in all, but one of the literature proposals, with a threshold for withdrawal in most cases (n = 17) and/or adjustment of the metformin dose as a function of renal status (n = 8). There was a good degree of consensus on serum creatinine thresholds; whereas guidelines based on estimated glomerular filtration rate thresholds varied from 60 mL/minute/1.73 m(2) up to stage 5 CKD. Only one of the proposals has been tested in a prospective study.

CONCLUSIONS

In general, proposals for continuing or stopping metformin therapy in CKD involve a threshold (whether based on serum creatinine or estimated glomerular filtration rate) rather than the dose adjustment as a function of renal status (in stable patients) performed for other drugs excreted by the kidney.

Proposal for the administration of metformin in patients with chronic kidney disease

Metformin is the first-line, widely used oral antidiabetic agent for the management of type 2 diabetes. There is increasing evidence that metformin use results in a reduction in cardiovascular morbidity and mortality, and might have anticancer activity. An extremely rare, but potentially life-threatening adverse effect of metformin is lactic acidosis, therefore, its use is traditionally contraindicated if the glomerular filtrate rate is below 60 mL/min. However, lactic acidosis is always associated with acute events, such as hypovolemia, acute cardiorespiratory illness, severe sepsis and acute renal or hepatic failure. Furthermore, administration of insulins and conventional antihyperglycemic agents increases the risk of severe hypoglycemic events when renal function is reduced. Therefore, the magnitude of the benefit of metformin use would outweigh potential risk of lactic acidosis in moderate chronic renal disease. After reviewing the literature, the authors give a proposal for the administration of metformin, according to the calculated glomerular filtrate rate. Orv.Hetil., 2012, 153, 1527–1535.

Transitioning from inpatient to outpatient therapy in patients with in-hospital hyperglycemia

Transition from inpatient to outpatient care for patients with type 2 diabetes mellitus is an important aspect of patient management for which there is no guidance. Intensive glucose lowering with insulin is generally favored for seriously ill hospitalized patients, but after discharge, patients often resume their prior regimens, which may include an array of oral or injected glucose-lowering agents. Factors that should be considered in this transition include goals of care/life expectancy, glycated hemoglobin at hospital admission, home medications for other illnesses and their potential for interactions with antidiabetes treatment, comorbidities, nutritional status, physical disabilities, ability to carry out self-monitoring of blood glucose, risk for hypoglycemia, contraindications to oral medications, health literacy, and financial and other resources. Traditional oral therapies that may be used after the patient leaves the hospital include sulfonylureas, α-glucosidase inhibitors, thiazolidinediones, and metformin. α-Glucosidase inhibitors are limited by gastrointestinal adverse events, and thiazolidinediones by fluid retention and increased risk for heart failure. Thiazolidinediones also require a long period of administration for onset glucose lowering and are not suitable for transitioning hospitalized patients who have been receiving insulin to outpatient care. Metformin is contraindicated in patients with renal, cardiac, or pulmonary insufficiency. Incretin-based therapies, glucagon-like peptide-1 receptor agonists and dipeptidyl peptidase-4 inhibitors, have limited use in hospitals, but may be suitable for the transition to outpatient treatment. The most common adverse events with glucagon-like peptide-1 inhibitors involve the gastrointestinal system. More formal studies of treatment regimens for patients with hyperglycemia leaving the hospital are needed to guide care for this group.

Contrast induced nephropathy: updated ESUR Contrast Media Safety Committee guidelines

PURPOSE

The Contrast Media Safety Committee (CMSC) of the European Society of Urogenital Radiology (ESUR) has updated its 1999 guidelines on contrast medium-induced nephropathy (CIN).

AREAS COVERED

Topics reviewed include the definition of CIN, the choice of contrast medium, the prophylactic measures used to reduce the incidence of CIN, and the management of patients receiving metformin. Key Points • Definition, risk factors and prevention of contrast medium induced nephropathy are reviewed. • CIN risk is lower with intravenous than intra-arterial iodinated contrast medium. • eGFR of 45 ml/min/1.73 m (2) is CIN risk threshold for intravenous contrast medium. • Hydration with either saline or sodium bicarbonate reduces CIN incidence. • Patients with eGFR ≥ 60 ml/min/1.73 m (2) receiving contrast medium can continue metformin normally.

Estimation of renal function in patients with diabetes

Diabetes is the leading cause of chronic kidney disease (CKD), which makes estimation of renal function crucial. Serum creatinine is not an ideal marker of glomerular filtration rate (GFR), which also depends on digestive absorption, and the production of creatinine in muscle and its tubular secretion. Formulas have been devised to estimate GFR from serum creatinine but, given the wide range of GFR, proteinuria, body mass index and specific influence of glycaemia on GFR, the uncertainty of these estimations is a particular concern for patients with diabetes. The most popular recommended formulas are the simple Cockcroft-Gault equation, which is inaccurate and biased, as it calculates clearance of creatinine in proportion to body weight, and the MDRD equation, which is more accurate, but systematically underestimates normal and high GFR, being established by a statistical analysis of results from renal-insufficient patients. This underestimation explains why the MDRD equation is repeatedly found to give a poor estimation of GFR in patients with recently diagnosed diabetes and is a poor tool for reflecting GFR decline when started from normal, as well as the source of unexpected results when applied to epidemiological studies with a 60mL/min/1.73m(2) threshold as the definition of CKD. The more recent creatinine-based formula, the Mayo Clinic Quadratic (MCQ) equation, and the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) improve such underestimation, as both were derived from populations that included subjects with normal renal function. Determination of cystatin C is also promising, but needs standardisation.

Lactic acidosis induced by metformin: incidence, management and prevention

Lactic acidosis associated with metformin treatment is a rare but important adverse event, and unravelling the problem is critical. First, this potential event still influences treatment strategies in type 2 diabetes mellitus, particularly in the many patients at risk of kidney failure, in those presenting contraindications to metformin and in the elderly. Second, the relationship between metformin and lactic acidosis is complex, since use of the drug may be causal, co-responsible or coincidental. The present review is divided into three parts, dealing with the incidence, management and prevention of lactic acidosis occurring during metformin treatment. In terms of incidence, the objective of this article is to counter the conventional view of the link between metformin and lactic acidosis, according to which metformin-associated lactic acidosis is rare but is still associated with a high rate of mortality. In fact, the direct metformin-related mortality is close to zero and metformin may even be protective in cases of very severe lactic acidosis unrelated to the drug. Metformin has also inherited a negative class effect, since the early biguanide, phenformin, was associated with more frequent and sometimes fatal lactic acidosis. In the second part of this review, the objective is to identify the most efficient patient management methods based on our knowledge of how metformin acts on glucose/lactate metabolism and how lactic acidosis may occur (at the organ and cellular levels) during metformin treatment. The liver appears to be a key organ for both the antidiabetic effect of metformin and the development of lactic acidosis; the latter is attributed to mitochondrial impairment and subsequent adenosine triphosphate depletion, acceleration of the glycolytic flux, increased glucose uptake and the generation of lactate, which effluxes into the circulation rather than being oxidized further. Haemodialysis should systematically be performed in severe forms of lactic acidosis, since it provides both symptomatic and aetiological treatment (by eliminating lactate and metformin). In the third part of the review (prevention), the objective is to examine the list of contraindications to metformin (primarily related to renal and cardiovascular function). Diabetes is above all a vascular disease and metformin is a vascular drug with antidiabetic properties. Given the importance of the liver in lactate clearance, we suggest focusing on the severity of and prognosis for liver disease; renal dysfunction is only a prerequisite for metformin accumulation, which may only be dangerous per se when associated with liver failure. Lastly, in view of metformin's impressive overall effectiveness profile, it would be paradoxical to deny the majority of patients with long-established diabetes access to metformin because of the high prevalence of contraindications. The implications of these contraindications are discussed.

Status of diabetes management in the nursing home setting in 2008: a retrospective chart review and epidemiology study of diabetic nursing home residents and nursing home initiatives in diabetes management

PURPOSE

Diabetes mellitus (DM) is associated with significant morbidity and mortality, and can present with atypical signs and symptoms in elderly residents of nursing homes who often have altered functional and cognitive capacity representing a particularly challenging population to manage. Researchers conducted this study to better understand the current status of DM management in the long-term care facility from the perspective of the facility (use of guidelines, policies, and so forth) as well as that of a resident.

METHODS

Thirteen nursing home facilities in 6 states were studied. A 13-question survey instrument was used to collect data from interviews of the directors of nursing and medical directors. A 26-question data collection form was also used to perform a retrospective chart review of studied residents.

RESULTS

Data from the interview surveys showed that only 15% of facilities studied had a policy for the use of treatment algorithms to manage residents with DM. In addition, only 1 of 13 facilities had a quality improvement tool to evaluate compliance with current policies. In regard to hemoglobin A1C (A1C) testing, only 7.1% of facilities had a house policy in place. Furthermore, only 1% of studied residents had an established target for their A1C despite American Diabetes Association (ADA), American Geriatrics Society (AGS), and American Medical Directors Association (AMDA) guidelines recommending target values and monitoring frequency for A1C testing. The survey instrument also found that just 30.8% of facilities had a policy in place for blood glucose monitoring. Data from the chart review shows that only 57% of residents in this study were taking aspirin or clopidogel bisulfate, although prevention of cardiovascular disease (CVD) is recommended by the American Heart Association (AHA) and ADA in persons with diabetes who are older than 40. Data from this study indicate serious hypoglycemia occurs only occasionally in the nursing home because hypoglycemic episodes requiring hospitalization occurred in only 1% of studied residents. Furthermore, researchers found each of these residents were sent to the hospital only once in the preceding 6 months. One unanticipated finding of the study reports the incidence of delusions from patients' Minimum Data Set (MDS) was 87.63% compared with the national average of 3.7%.

CONCLUSION

Data obtained through this study demonstrates numerous opportunities for improvement in the quality of care for nursing home residents with DM. A multidisciplinary approach is required to properly manage this complex disease in a challenging elderly population. The development of protocols and tools that embrace the latest strategies and treatment algorithms for the management of DM in the geriatric resident are necessary, while implementation of a quality improvement tool can help facilities to further improve on management of DM in the long-term care setting.

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.