Identifying prevalence and risk factors for metformin non-persistence: a retrospective cohort study using an electronic health record

Clinical efficacy and cost-effectiveness of metformin in different patient populations: A narrative review of real-world evidence

Over the past two decades, diabetes pharmacopoeia has flourished, with new drugs that, on top of their glucose-lowering efficacy, have been shown to protect the heart and the kidney. Despite these new opportunities, metformin retains a pivotal role among glucose-lowering agents. As one of the few available insulin sensitizers, metformin is an effective, safe, and overall well-tolerated drug backed by over 60 years of clinical experience, including evidence for potential benefits beyond glucose reduction across different ages, sexes, genetic backgrounds, geographical areas, and stages of disease. Although there is some discussion of whether metformin offers the most effective front-line option in newly diagnosed type 2 diabetes (T2D), it remains a natural companion to all other glucose-lowering agents. Furthermore, metformin comes at a very low cost and, as such, it has extremely high cost-effectiveness, particularly given the serious economic burden associated with diabetes complications. This financial advantage is particularly relevant in resource-constrained healthcare systems, where the affordability of metformin may be instrumental in implementing an effective treatment in an evergrowing number of individuals. We present here compelling real-world evidence in support of the clinical efficacy and cost-effectiveness of metformin across different patient populations, highlighting areas where more population-based studies are needed to further incorporate and consolidate its use in the pharmacological management of T2D.

New evidence: Metformin unsuitable as routine adjuvant for breast cancer: a drug-target mendelian randomization analysis

PURPOSE

The potential efficacy of metformin in breast cancer (BC) has been hotly discussed but never conclusive. This genetics-based study aimed to evaluate the relationships between metformin targets and BC risk.

METHODS

Metformin targets from DrugBank and genome-wide association study (GWAS) data from IEU OpenGWAS and FinnGen were used to investigate the breast cancer (BC)-metformin causal link with various Mendelian Randomization (MR) methods (e.g., inverse-variance-weighting). The genetic association between type 2 diabetes (T2D) and the drug target of metformin was also analyzed as a positive control. Sensitivity and pleiotropic tests ensured reliability.

RESULTS

The primary targets of metformin are PRKAB1, ETFDH and GPD1L. We found a causal association between PRKAB1 and T2D (odds ratio [OR] 0.959, P = 0.002), but no causal relationship was observed between metformin targets and overall BC risk (PRKAB1: OR 0.990, P = 0.530; ETFDH: OR 0.986, P = 0.592; GPD1L: OR 1.002, P = 0.806). A noteworthy causal relationship was observed between ETFDH and estrogen receptor (ER)-positive BC (OR 0.867, P = 0.018), and between GPD1L and human epidermal growth factor receptor 2 (HER2)-negative BC (OR 0.966, P = 0.040). Other group analyses did not yield positive results.

CONCLUSION

The star target of metformin, PRKAB1, does not exhibit a substantial causal association with the risk of BC. Conversely, metformin, acting as an inhibitor of ETFDH and GPD1L, may potentially elevate the likelihood of developing ER-positive BC and HER2-negative BC. Consequently, it is not advisable to employ metformin as a standard supplementary therapy for BC patients without T2D.

Measuring the Influence of Side Effect Expectations, Beliefs, and Incident Side Effects on the Risk for Drug Discontinuation Among Individuals Starting New Medications, a Cross-sectional Study

Purpose

To measure the impact of beliefs, expectations, side effects, and their combined effects on the risk for medication nonpersistence.

Patients and methods

Using a cross-sectional design, individuals from Saskatchewan, Canada who started a new antihypertensive, cholesterol-lowering, or antihyperglycemic medication were surveyed about risk factors for nonpersistence including: (a) beliefs measured by a composite score of three questions asking about the threat of the condition, importance of the drug, and harm of the drug; (b) incident side effects attributed to treatment; and (c) expectations for side effects before starting treatment. Descriptive statistics and logistic regression models were used to quantify the influence of these risk factors on the outcome of nonpersistence. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated.

Results

Among 3,029 respondents, 5.8% (n=177) reported nonpersistence within four months after starting the new drug. After adjustment for numerous covariates representing sociodemographics, health-care providers, medication experiences and beliefs, both negative beliefs (OR: 7.26, 95%CI: 4.98-10.59) and incident side effects (OR: 8.00, 95%CI: 5.49-11.68) were associated with the highest odds of nonpersistence with no evidence of interaction. In contrast, expectations for side effects before starting treatment exhibited an important interaction with incident side effects following treatment initiation. Among respondents with incident side effects (n=741, 24.5%), the risk for early nonpersistence was 11.5% if they indicated an expectation for side effects before starting the medication compared to 23.6% if they did not (adjusted OR: 0.38, 95%CI: 0.25-0.60).

Conclusion

Expectations for side effects may be a previously unrecognized but important marker of the probability to persist with treatment. A high percentage of new medication users appeared unprepared for the possibility of side effects from their new medication making them less resilient if side effects occur.

Microbiome differences related to metformin intolerance among Black individuals with diabetes, a pilot cross-sectional study

Aims

Metformin is the broadly accepted the first-line medication for diabetes. Its use, however, is limited by gastrointestinal side effects present in approximately 25% of patients. This study aimed to better understand the interplay between metformin intolerance and gut microbiota among Black individuals with diabetes.

Methods

We performed a cross-sectional study among 29 Black individuals living with diabetes with or without metformin intolerance. Participants with mean age 59±11, 58% female, were stratified into three groups: 1)intolerant: metformin intolerance in the past, not on metformin; 2)partially intolerant: mild to moderate gastrointestinal symptoms, currently taking metformin 3)tolerant: using metformin without symptoms. We collected and analyzed rectal swabs and analyzed microbiota composition using V3-V4 regions of the 16s rRNA.

Results

Metformin intolerant subjects trended towards having greatest alpha diversity, followed by tolerant and partially tolerant (Intolerant:4.9; Tolerant:4.2; Partially tolerant:3.9). Mean difference in alpha diversity for intolerant versus partially tolerant was 1.0 (95% CI-0.1,2.1) and intolerant versus tolerant were 0.7 (95% CI -0.4,1.8).

Conclusion

This was the first study to evaluate the role of microbiota and metformin intolerance among Black individuals. We report on differences in alpha diversity as well as microbiota composition.

Metformin Cessation and Dementia Incidence

Importance

Prior studies suggested that metformin may be associated with reduced dementia incidence, but associations may be confounded by disease severity and prescribing trends. Cessation of metformin therapy in people with diabetes typically occurs due to signs of kidney dysfunction but sometimes is due to less serious adverse effects associated with metformin.

Objective

To investigate the association of terminating metformin treatment for reasons unrelated to kidney dysfunction with dementia incidence.

Design, Setting, and Participants

This cohort study was conducted at Kaiser Permanente Northern California, a large integrated health care delivery system, among a cohort of metformin users born prior to 1955 without history of diagnosed kidney disease at metformin initiation. Dementia follow-up began with the implementation of electronic health records in 1996 and continued to 2020. Data were analyzed from November 2021 through September 2023.

Exposures

A total of 12 220 early terminators, individuals who stopped metformin with normal estimated glomerular filtration rate (eGFR), were compared with routine metformin users, who had not yet terminated metformin treatment or had terminated (with or without restarting) after their first abnormal eGFR measurement. Early terminators were matched with routine users of the same age and gender who had diabetes for the same duration.

Main outcomes and measures

The outcome of interest was all-cause incident dementia. Follow-up for early terminators and their matched routine users was started at age of termination for the early terminator. Survival models adjusted for sociodemographic characteristics and comorbidities at the time of metformin termination (or matched age). Mediation models with HbA1c level and insulin usage 1 and 5 years after termination tested whether changes in blood glucose or insulin usage explained associations between early termination of metformin and dementia incidence.

Results

The final analytic sample consisted of 12 220 early terminators (5640 women [46.2%]; mean [SD] age at start of first metformin prescription, 59.4 [9.0] years) and 29 126 routine users (13 582 women [46.6%]; mean [SD] age at start of first metformin prescription, 61.1 [8.9] years). Early terminators had 1.21 times the hazard of dementia diagnosis compared with routine users (hazard ratio, 1.21; 95% CI, 1.12 to 1.30). In mediation analysis, contributions to this association by changes in HbA1c level or insulin use ranged from no contribution (0.00 years; 95% CI, -0.02 to 0.02 years) for insulin use at 5 years after termination to 0.07 years (95% CI, 0.02 to 0.13 years) for HbA1c level at 1 year after termination, suggesting that the association was largely independent of changes in HbA1c level and insulin usage.

Conclusions and Relevance

In this study, terminating metformin treatment was associated with increased dementia incidence. This finding may have important implications for clinical treatment of adults with diabetes and provides additional evidence that metformin is associated with reduced dementia risk.

Metformin, placebo, and endocrine therapy discontinuation among participants in a randomized double-blind trial of metformin vs placebo in hormone receptor-positive early-stage breast cancer (CCTG MA32)

BACKGROUND

The MA32 study investigated whether 5 years of metformin (versus placebo) improves invasive disease-free survival in early-stage breast cancer (BC). Non-adherence to endocrine therapy (ET) and medications for chronic conditions is common and increases with drug toxicity and polypharmacy. This secondary analysis evaluates rates and predictors of early discontinuation of metformin, placebo, and ET among participants with HR-positive BC.

METHODS

Patients with high-risk non-metastatic BC were randomized to 60 months of metformin (850 mg BID) or placebo BID. Patients were administered bottles of metformin/placebo every 180 days. Metformin/placebo adherence was defined as a bottle dispensed at month 48 or later. The ET adherence analysis included patients with HR-positive BC who received ET with start and stop date reported, with adherence defined as > 48 months of use. Associations of covariates with study drug and ET adherence were examined using multivariable models.

RESULTS

Among the 2521 HR-positive BC patients, 32.9% were non-adherent to study drug. Non-adherence was higher among patients on metformin vs placebo (37.1% vs 28.7%, p < 0.001). Reassuringly, ET discontinuation rates were similar between treatment arms (28.4% vs 28.0%, p = 0.86). Patients who were non-adherent to ET were more likely to discontinue study therapy (38.8% vs 30.1%, p < 0.0001). In a multivariable analysis, study drug non-adherence was increased with metformin vs placebo (OR: 1.50, 95% CI 1.25-1.80; p < 0.0001); non-adherence to ET (OR: 1.47, 95% CI 1.20-1.79, p < 0.0001); grade 1 or greater GI toxicity during the first 2 years; lower age; and higher body mass index.

CONCLUSION

While non-adherence was higher among patients on metformin, it was still considerable among patients on placebo. Reassuringly, treatment arm allocation did not impact ET adherence. Attention to global medication adherence is needed to improve BC and non-oncological outcomes in cancer survivors.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT01.

Predictors of Metformin Side Effects in Patients with Newly Diagnosed Type 2 Diabetes Mellitus

Introduction Metformin has become the first-line agent for the treatment of type 2 diabetes mellitus (T2DM) in several international guidelines. Up to 25% of patients suffer from gastrointestinal side-effects, with approximately 5% unable to tolerate metformin at all.

Objective We aimed to study the effect of variables that may influence the development of metformin side effects and/or intolerance.

Method A prospective study was conducted from April 1, 2021 to March 30, 2022. One-hundred and forty-eight patients newly diagnosed with T2DM were enrolled in the study, and divided into two groups—those who were escalate to the maximum dose of metformin over 2 weeks (n = 43) and the other group over 4 weeks (n = 105). We studied the variables that may affect the development of side effects including age, gender, body mass index (BMI), lipid profile, glycemic level, and the use of other antidiabetic medications besides the duration of dose escalation.

Results Total number of patients who developed side effects was 59 (39.9%). Twenty-four (55.8%) and 35 (33.3%) patients were put in the rapid and slow escalation groups, respectively. Twenty-six (17.6%) patients developed diarrhea that was the most common side effect. Two (2.7%) men and ten women (13.5%) had stopped metformin due to severe side effects developed after initiation (p = 0.016). The mean BMI for the patients who discontinued metformin was 34.7 ± 4.1 kg/m2 in the rapid escalation arm and 31.6 ± 3.3 kg/m2 in the slow escalation arm (p = 0.003). The mean of fasting blood glucose for the patients who discontinued metformin in the rapid and slow escalation arms was 200.6 ± 25.6 and 173.4 ± 36.5 mg/dL, respectively (p = 0.022).

Conclusion The severity of metformin side effects is higher in women than in men, making more women to discontinue the drug. Besides, a higher fasting blood sugar and BMI are associated with a higher rate of discontinuation. A rapid dose escalation is associated with a higher frequency of side effects. Diarrhea is the commonest side effect encountered.

Budget Impact Analysis of Empagliflozin in the Treatment of Patients With Type 2 Diabetes With Established Cardiovascular Disease in South Africa

OBJECTIVES

This study aimed to estimate the budget impact and affordability of empagliflozin added to usual care compared with usual care alone, in a diabetic population with established cardiovascular disease, from a private healthcare payer perspective in South Africa.

METHODS

A budget impact model was adapted and localized. Epidemiological data were obtained from the South African Council for Medical Schemes. Clinical event rates were sourced from the EMPA-REG OUTCOME trial and drug costs from list prices. Clinical event costs were derived from a claims data analysis of the South African private healthcare sector and microcosting. Scenario analyses were performed on select inputs. The modeled outcomes included annual budget impact of empagliflozin, the incremental cost per life per month, cardiovascular deaths averted, and incremental cost per life saved, over 3 years.

RESULTS

A total of 9 503 patients were eligible for empagliflozin (year 1), 12 670 (year 2), and 16 947 (year 3). The incremental cost was $1 272 297, $1 764 705, and $2 455 235, for years 1 to 3, respectively. The incremental cost per beneficiary per month was calculated as $0.012 (year 1), $0.016 (year 2), and $0.023 (year 3). The model estimated a 38.6% reduction in cardiovascular deaths, 305 lives saved, and an incremental cost per life saved of $17 999.

CONCLUSIONS

Adding empagliflozin to usual care has a marginal budget implication and is highly affordable for private healthcare payers, with an acceptable incremental cost based on clinical outcomes.

Adherence and persistence rates of major antidiabetic medications: a review

The objective of this paper was to review the adherence and persistence rates of major antidiabetic medication classes (i.e., metformin, sulfonylureas, sodium glucose cotransporter-2 inhibitors, dipeptidyl peptidase-4 inhibitors, insulin, glucagon-like peptide-1 receptor agonists, and thiazolidinediones) by summarizing the major findings of the studies published since 2017. In addition, we reported the potential causes for low adherence and persistence of antidiabetic medications. Based on the literature, the highest rate of adherence and persistence was consistently observed in metformin users. Second to metformin were sodium glucose cotransporter-2 inhibitors. Injectable therapies such as insulin and glucagon-like peptide-1 receptor agonists trailed low on the adherence and persistence rates. To the best of our knowledge, no studies published since the year 2017 analyzed the adherence and persistence of thiazolidinediones independently. The most frequently cited cause for low adherence and persistence was the severity of adverse events. Baseline characteristics (e.g., baseline HbA1c level), demographic information (e.g., age, gender, or ethnicity), and comorbidity profiles also had significant impacts on adherence and persistence in patients with type 2 diabetes mellitus.

Factors associated with early nonpersistence among patients experiencing side effects from a new medication

BACKGROUND

Drug discontinuation (i.e., nonpersistence) is often attributed to the emergence of adverse effects. However, it is not known whether other factors increase the risk of nonpersistence when adverse effects occur.

OBJECTIVES

To identify factors associated with early nonpersistence among patients experiencing adverse effects from newly prescribed medications.

METHODS

A questionnaire was mailed to new users of antihypertensive, antihyperglycemic, and lipid-lowering medications in Saskatchewan, Canada, between 2019 and 2020. Only respondents experiencing adverse effects were included. Responses were compared between the nonpersistent group (i.e., people who had discontinued their medication) and the persistent group (i.e., those who were taking their medication at the time of the survey). Statistically significant factors were tested in multivariable logistic regression models. Odds ratios (ORs) and 95% CIs were reported.

RESULTS

Of the 3973 returned questionnaires, 813 respondents experienced adverse -effects from their new medication and were included in the study. Of these, 143 respondents (17.5%) had stopped their medication at the time of survey completion; most discontinuations (72.1%) occurred within 1 month of the first dose. Nonpersistent patients were older, had lower income, and were less likely to be taking an antihyperglycemic medication. After covariate adjustment, 6 factors were independently associated with nonpersistence: age less than 65 years (OR 1.56 [95% CI 1.01-2.41]), female sex (1.67 [1.08-2.59]), health condition not considered dangerous (2.09 [1.25-3.51]), medication not considered important for health (6.90 [4.40-10.84]), failure to expect adverse effects before starting medication (2.67 [1.74-4.10]), and taking 2 or more medications (0.45 [0.27-0.73]).

CONCLUSION

Despite the strong link between the emergence of adverse effects and early nonpersistence, our findings confirm that this association is highly influenced by several factors external to the physical experiences caused by the new medication.

[Treatment persistence with brand-name vs. generic metformin in monotherapy for type 2 diabetes: real-life retrospective study using the propensity matching score]

OBJECTIVE

To evaluate treatment persistence in patients with polymedicated type 2 diabetes (DM2) receiving new treatment with brand-name vs. generic metformin 850mg in usual clinical practice.

PATIENTS AND METHODS

Observational, retrospective study based on the medical records of patients aged ≥50 years who initiated metformin treatment (brand-name vs. generic) between 01/01/2016 and 31/12/2017. The follow up was two years.

MAIN MEASURES

treatment persistence and clinical consequences (metabolic control [HbA1c] and hospital admissions). Each patient in the brand-name group (reference) was paired with a patient from the generic group using propensity score matching. A Cox proportional risk model was constructed (p<0.05).

RESULTS

863 patients receiving brand-name metformin were matched (ratio 1:1) with patients receiving generic metformin. The median age was 60.8 years (SD: 8.8) years and 52.6% were female. Persistence at 24 months was 8.6% higher for brand-name vs. generic metformin (63.2% vs. 58.2%; p=0.034). The hazard ratio for brand-name metformin was 0.83 (95% CI: 0.71-0.96, p=0.013). During the follow-up there was a greater percentage reduction of HbA1c in the brand-name vs. generic group (-6.8% vs. -4.1%; p=0.013). There was a non-significant 19.1% reduction in hospital admissions in the brand-name vs. generic group (8.9% vs. 11.0%; p=0.148).

CONCLUSIONS

Polymedicated patients who initiated new brand-name metformin treatment for DM2 had greater treatment persistence than those who initiated it with generic metformin and had better metabolic control (percentage reduction in HbA1c).

Metformin decreases bacterial trimethylamine production and trimethylamine N-oxide levels in db/db mice

The current study aimed to explore whether metformin, the most widely prescribed oral medication for the treatment of type 2 diabetes, alters plasma levels of cardiometabolic disease-related metabolite trimethylamine N-oxide (TMAO) in db/db mice with type 2 diabetes. TMAO plasma concentration was up to 13.2-fold higher in db/db mice when compared to control mice, while in db/db mice fed choline-enriched diet, that mimics meat and dairy product intake, TMAO plasma level was increased 16.8-times. Metformin (250 mg/kg/day) significantly decreased TMAO concentration by up to twofold in both standard and choline-supplemented diet-fed db/db mice plasma. In vitro, metformin significantly decreased the bacterial production rate of trimethylamine (TMA), the precursor of TMAO, from choline up to 3.25-fold in K. pneumoniae and up to 26-fold in P. Mirabilis, while significantly slowing the growth of P. Mirabilis only. Metformin did not affect the expression of genes encoding subunits of bacterial choline-TMA-lyase microcompartment, the activity of the enzyme itself and choline uptake, suggesting that more complex regulation beyond the choline-TMA-lyase is present. To conclude, the TMAO decreasing effect of metformin could be an additional mechanism behind the clinically observed cardiovascular benefits of the drug.

Use of oral antidiabetic drugs in Japanese working-age patients with type 2 diabetes mellitus: dosing pattern for metformin initiators

Objective: To determine the pattern of antidiabetic drug use, with a particular focus on the metformin dose, among patients with type 2 diabetes mellitus (T2DM) in a Japanese working population.Methods: We used an administrative claims database linked to yearly health check-up data from large corporations. Data were collected for T2DM patients who began using an antidiabetic drug between 2014 and 2017 (n = 20,401). We evaluated the type of antidiabetic drug used and the characteristics of the patients using each type of drug. Among the metformin users, we assessed the titration in its dose or treatment during the 12 month period after initiation at 3 month intervals.Results: Among 20,401 new antidiabetic users, the most frequently used agents during the study period were dipeptidyl peptidase-4 inhibitors (DPP4is; 47.4%), followed by biguanides (18.5%) and sodium glucose cotransporter-2 inhibitors (SGLT2is; 6.7%). Most patients who initiated with metformin were prescribed 500 mg or less daily (72.9%); only 2.0% were prescribed a daily dose of >1000 mg. Moreover, 27% remained on the same daily dose during the 1 year follow-up, whereas another 29.9% discontinued their antidiabetic treatment altogether.Conclusions: A unique pattern of prescription was observed amongst Japanese patients with T2DM, and DPP4is, rather than metformin, were predominantly used as the first-line treatment. SGLT2is were infrequently prescribed. Metformin was prescribed at a daily dose of ≤500 mg in many patients. Greater efforts are needed to assess the comparative effectiveness of these treatment strategies.

Overcoming barriers to the use of metformin: patient and provider perspectives

BACKGROUND

Metformin is the first-line treatment for type 2 diabetes mellitus. Observational studies show lower rates of use than would be expected from clinical guidelines.

OBJECTIVE

We undertook a qualitative study of barriers to metformin use from the patient and provider perspective.

DESIGN

Patient focus group, patient individual interviews, provider interviews, and chart review. Purposive sampling of patients and providers in New York State.

PARTICIPANTS

Seven one-on-one patient interviews, one focus group with 13 patients, 10 provider interviews, and manual review of 1259 charts.

APPROACH

Grounded theory.

RESULTS

Both providers and patients cited potential health benefits as strong reasons to take metformin and describe it as the first-line drug for diabetes. Patients and providers both cited gastrointestinal side effects as the primary barrier to metformin use. Patients described adapting to these side effects and taking metformin at a time that minimizes them. In contrast, providers emphasized dose titration and the use of extended-release formulation as tools for minimizing side effects but were uncertain about the effectiveness of these strategies.

CONCLUSION

Metformin is positively viewed by patients and providers, but gastrointestinal side effects are a barrier to its use. There is some consensus on basic measures to improve its tolerability, but these measures are not consistently applied and lack evidence establishing their effectiveness. Pragmatic clinical trial research on optimal dose, formulation, and counseling for new metformin users should be considered.