Individualizing Treatment of Hyperglycemia in Type 2 Diabetes

Add Additional Agent(s) as Needed to Achieve Goal

Other than metformin, evidence is limited for the optimal use of the burgeoning array of available agents, especially in dual or triple combinations [6,30]. Research is now starting to focus more on what the ideal number and sequence of drugs should be. The Glycemic Reduction Approach in Diabetes (GRADE) study, which will compare long-term benefits and risks of the 4 most widely used antihyperglycemic medications in combination with metformin, is now underway [31,32]. The 4 classes being studied are sulfonylurea, dipeptidyl peptidase-4 (DPP-4) inhibitors, glucagon-like peptide-1 (GLP-1) receptor agonists, and a basal, 

long-acting insulin. From a practical standpoint, investigating all possible combinations in diverse patient populations is not feasible. Physicians therefore must continue to rely on clinical judgment to determine how to apply trial data to the treatment of individual patients.

Eleven classes of non-insulin medications are currently approved for treating hyperglycemia in T2DM [4]. Within each class, numerous agents are available. Six of these classes (ie, α-glucosidase inhibitors, colesevelam, bromocriptine, pramlintide, meglitinides, and thiazolidinediones) are not used frequently 

because of their modest efficacy, inconvenient frequency of administration, and/or limiting side effects. The 4 most commonly used non-insulin antihyperglycemic drug classes that can be added to metformin or used if a patient cannot tolerate metformin include the sulfonylureas, DPP-4 inhibitors, GLP-1 receptor agonists, and sodium-glucose cotransporter-2 (SGLT-2) inhibitors. Because T2DM is a progressive disease, many patients eventually may require insulin to achieve their glycemic goals. The primary characteristics of commonly used non-insulin agents are summarized in Table 4 [4,6,29,30,33–37] and the properties of FDA-approved insulins are summarized in Table 5 [37,38].

Consider Effects on A1C

There is a paucity of high-quality, head-to-head comparison trials evaluating the ability of available agents to achieve recommended glycemic targets. This is important because the glucose-lowering effectiveness of individual medications is strongly influenced by baseline characteristics such as A1C, duration of diabetes, and previous therapy. With these limitations in mind, the relative glucose-lowering effectiveness of commonly used agents is shown in Table 4. When used as monotherapy, A1C reductions of approximately 1% to 1.5% are achieved with metformin, sulfonylureas, and GLP-1 receptor agonists [6,30,34,35,39]. DPP-4 inhibitors and SGLT-2 inhibitors have more modest glucose-lowering efficacy, with A1C reductions of approximately 0.5% to 1% [6,30,34,35,39]. Larger effects may be seen in individuals with higher baseline A1C and those who are drug naïve. Insulin is the most effective glucose-lowering agent—it can reduce virtually any level of A1C down to the normal range, with hypoglycemia being the only limiting factor. When a patient has uncontrolled hyperglycemia on metformin monotherapy, or if there is a contraindication or intolerance to metformin, clinicians should consider the potential glucose-lowering effects of other available options and should choose an agent that conceivably could bring a patient close to meeting their treatment goal.

Eliminate Options with Unacceptable Adverse Effects

When the pharmacologic options with acceptable A1C-lowering potential have been identified, the ones with contraindications and potential serious adverse effects for the individual patient can immediately be eliminated (Table 4). For example, if a patient has an eGFR < 30 mL/min/1.73 m², metformin, sulfonylureas, GLP-1 receptor agonists, most DPP-4 inhibitors, and SGLT-2 inhibitors are either contraindicated or should be used with caution. In patients with severe osteoporosis, SGLT-2 inhibitors may not be the best option. In patients with a history of diabetic ketoacidosis (DKA), caution should be used with metformin and SGLT-2 inhibitors. There have been concerns of possible acute pancreatitis and neoplasia with the incretin-based agents, the DPP-4 inhibitors and GLP-1 receptor agonists [40,41], although other clinical trials and observational data have not found increased risk [42–45]. Nevertheless, these agents potentially should be avoided in patients with a history of pancreatitis or neoplasm. SGLT-2 inhibitors may be associated with genitourinary infections and volume depletion [46–48] and probably should be avoided in patients at high risk for these conditions.

If the adverse effects are not serious, changing the way the medication is administered may allow the patient to tolerate agents with high potential benefits. For example, metformin is commonly associated with gastrointestinal (GI) adverse effects, which can be reduced or avoided with slow titration of the dose [6] or by switching to an extended-release formulation [49]. GLP-1 receptor agonists are associated with GI adverse effects [6] and in most cases slow titration is recommended.

Evaluate Potential Risks/Benefits of Remaining Options

Hypoglycemia. The barrier of hypoglycemia generally precludes maintenance of euglycemia and full realization of the long-term benefits of good glucose control over a lifetime. Once considered a trivial issue, concerns about hypoglycemia in T2DM are increasingly being raised [19,50–55]. Clearly, hypoglycemia occurs more often as glycemic targets are lowered to near-normal values, especially in those with advanced age and multiple comorbidities [55]. Various comorbidities frequently encountered particularly as patients age also are associated with increasing propensity for experiencing hypoglycemia and untoward outcomes from it. These include coronary artery disease, heart failure, renal and liver disease, and dementia. Hypoglycemia, when it occurs, may lead to dysrhythmias, dizziness, accidents and falls, work disability, and decreased quality of life. In addition to relaxing blood glucose targets in high-risk patients, drug selection should favor agents that do not precipitate such events (Table 4).

Fortunately, the commonly used non-insulin agents are not associated with hypoglycemia unless they are used in combination with sulfonylureas or insulin. Sulfonylureas should be used with caution and other options considered in patients with high risk for hypoglycemia. When insulin is required, regimens which minimize risk of hypoglycemia should be used. For example, adding a GLP-1 receptor agonist to basal insulin as an alternative to mealtime insulin has been shown to be equally effective with a lower risk of hypoglycemia [4,6]. Also, premixed insulin preparations should be avoided or used cautiously in individuals who miss meals frequently. Additionally, newer basal insulins that exhibit longer duration of action are now available in the United States. Preliminary studies have shown that the newly FDA-approved longer-acting basal insulins, insulin degludec and glargine U-300, may be associated with a reduced risk for hypoglycemia [56,57]. However, it remains unclear how and when these newer agents will best be incorporated into a treatment regimen.

Body weight. Nearly 90% of people living with T2DM are overweight or obese. Given the close tie between obesity and T2DM, treating obesity is an obvious consideration in diabetes treatment. Major trials have shown the effectiveness of lifestyle modifications and weight reduction in delaying, prevention, and management of T2DM [4,58,59].With this in mind, clinicians should consider preferentially using antihyperglycemic agents with weight-lowering or weight-neutral effects. Among commonly used antihyperglycemic agents, metformin, GLP-1 receptor agonists, and SGLT-2 inhibitors have been shown to have weight-reduction benefits, and DPP-4 inhibitors are weight neutral. On the other hand, sulfonylureas and insulin are associated with weight gain. A systematic review and meta-analysis including 204 studies with study durations ranging from 3 months to 8 years showed comparative effects of diabetes medications with a differential effect on weight of up to 5 kg (Table 4) [60].

Metformin is associated with an average weight loss of 1.9 to 3.1 kg that was sustained with long-term use for at least 10 years in the Diabetes Prevention Program Outcomes Study [61].A systematic review of 7 randomized trials showed that in patients with T2DM, the SGLT-2 inhibitors dapagliflozin and canagliflozin were associated with weight loss (mean weighted difference of –1.81 kg and –2.3 kg, respectively) [62]. A systematic review and meta-analysis of 25 randomized controlled trials showed greater weight loss (mean weighted difference of –2.9 kg) in overweight or obese patients with or without T2DM using GLP-1 receptor agonists when compared to placebo, insulin, or oral antihyperglycemic agents [63]. Of note, the GLP-1 receptor agonist liraglutide is now approved for weight loss in patients with or without diabetes [64]. The maximum doses approved for diabetes and obesity treatment are 1.8 and 3.0 mg/day, respectively.

Since weight loss is associated with improved glycemic control, an area of emerging interest is the use of antiobesity medications for managing diabetes. Although most older weight-loss medications were only approved for short-term use, some newer agents are approved for longer-term use. Lorcaserin and the combination drugs topiramate/phentermine and naltrexone/bupropion are approved for chronic therapy, provided certain conditions are met. Patients on weight reduction agents should be monitored regularly. 

If weight loss of more than 5% is not achieved after 3 months of treatment, the therapy should be discontinued. Table 6 summarizes the efficacy and characteristics of FDA-approved weight loss medications [4,37,65–68].

An even more radical departure from conventional therapy for diabetes is the consideration of metabolic, or weight-loss, surgery, which has been found to be associated with rapid and dramatic improvements in blood glucose control. Metabolic surgery has been shown to improve glucose control more effectively than any known pharmaceutical or behavioral approach. For example, in an observational study of obese patients with T2DM, bariatric surgery led to diabetes remission rates of 72.3% 2 years after surgery and 30.4% 15 years after surgery compared to 16.4% and 6.5%, respectively, in control patients [69]. With long-term follow-up, significant decreases in microvascular and macrovascular complications were seen in the surgical group [69]. Compared with medical therapy alone, bariatric surgery plus medical therapy has been associated with more weight loss, better glycemic control, less need for diabetes medications, and improved quality of life [70]. A 2016 joint statement by numerous international diabetes organizations recommends considering metabolic surgery as a treatment for T2DM and obesity [71]. American Diabetes Association guidelines recommend consideration of bariatric surgery in individuals with T2DM who have a body mass index greater than 35 kg/m²,especially if achieving disease control is difficult by means of lifestyle modifications and medications [4].

Cardiovascular outcomes. Cardiovascular risk is about 2 to 4 times higher in patients with diabetes, and about half of patients with this condition develop heart failure [4,72]. CVD is responsible for most of the mortality in T2DM [72]. Therefore, prevention of cardiovascular morbidity and mortality is an important goal for diabetes treatment. Due to concerns about potential cardiovascular risks associated with glucose-lowering medications [73–76], the FDA has issued regulatory requirements for manufacturers to monitor the cardiovascular risk profile for these drugs [77]. Recent trials have led to a better understanding of potential cardiovascular benefits or harms of antihyperglycemic medications.

Metformin, the widely recommended first-line therapy for T2DM, carries a large body of evidence supporting its cardiovascular benefits. For example, the UKPDS found that compared to conventional therapy (mostly diet), metformin reduced cardiovascular events and mortality in obese patients with T2DM [15]. This result was supported in Hyperinsulinemia: the Outcome of its Metabolic Effect (HOME) study where, as an add-on to insulin, metformin decreased macrovascular complications when compared to placebo [78]. Research over the past decade also has assuaged concerns about metformin safety in heart failure [60]. A systematic review of observational studies involving 34,000 patients conducted in 2013 showed that metformin is as safe as other glucose-lowering medications in patients with diabetes and heart failure even in the presence of CKD [4,79]. Furthermore, numerous investigations have found metformin is not associated with increased hospitalizations or risk of lactic acidosis [80]. Metformin can be used safely in patients with diabetes and heart failure [60].

Although sulfonylureas have long been a mainstay of diabetes therapy, concerns about their potential adverse cardiovascular effects have been raised by numerous studies [81]. Tolbutamide, a first-generation sulfonylurea, was removed from the market after the University Group Diabetes Program study found increased CVD deaths with this agent versus placebo. Subsequently, the FDA issued a warning for all sulfonylureas [74]. The increased cardiovascular risk associated with sulfonylureas is thought to be due to their effect on cardiac mitochondrial potassium ATP channels. Sulfonylureas bind to these channels, preventing a protective phenomenon called ischemic preconditioning and resulting in a weakened defense against myocardial injury [76]. A recent study showed an increased risk of coronary heart disease associated with long-term use of sulfonylureas in women with diabetes [81].