Akshay B. Jain, MD
It’s that time of the year, when social media is rife with many top 5 and top 10 lists. Perhaps the beginning of a new year is a good time to review how different medications can have side effects beyond the disease state they’re used to address. Among the most common complications of many medications is the potential to disrupt glycemic control. Let’s revisit some of the most commonly used medications known to increase glucose levels and look at some practical tips on overcoming these.
Glucocorticoids
Without a doubt, corticosteroids are at the top of the list when it comes to the potential for increasing blood glucose levels. High-dose glucocorticoid therapy is known to lead to new-onset diabetes (steroid-induced diabetes). Similarly, people with preexisting diabetes may notice significant worsening of glycemic control when they start on glucocorticoid therapy. The extent of glucose elevation depends on their glycemic status prior to initiation on steroids, the dose and duration of glucocorticoid therapy, and comorbid conditions, among other factors.
Management tip: For those with previously well-controlled diabetes or borderline diabetes, glucocorticoid-induced hyperglycemia may be managed by metformin with or without sulfonylurea therapy, especially if corticosteroid treatment is low-dose and for a shorter duration. However, for many individuals with preexisting poorly controlled diabetes or those initiated on high-dose corticosteroids, insulin therapy would perhaps be the treatment of choice. Glucocorticoid therapy generally leads to more pronounced postprandial hyperglycemia compared with fasting hyperglycemia; hence, the use of short-acting insulin therapy or perhaps NPH insulin in the morning might be a better option for many individuals. Dietary modification plays an important role in limiting the extent of postprandial hyperglycemia. Use of continuous glucose monitoring (CGM) devices may also be very helpful for understanding glycemic excursions and how to adjust insulin. In individuals for whom glucocorticoid therapy is tapered down, it is important to adjust the dose of medications with potential to cause hypoglycemia, such as insulin/sulfonylurea therapy, as the degree of hyperglycemia may decrease with decreased dose of the glucocorticoid therapy.
Antipsychotic Therapy
Antipsychotic medications can be obesogenic; between 15% and 72% of people who take second-generation antipsychotics experience weight gain of 7% or more. Increases in weight are not the only factor contributing to an elevated risk of developing type 2 diabetes. Antipsychotics are thought to cause downregulation of intracellular insulin signaling, leading to insulin resistance. At the same time, there seems to be a direct effect on the pancreatic beta cells. Antagonism of the dopamine D2, serotonin 5-HT2C, and muscarinic M3 receptors impairs beta-cell response to changes in blood glucose. In addition to the pharmacologic effects, cell culture experiments have shown that antipsychotics increase apoptosis of beta cells. Increased weight and concomitant development of type 2 diabetes is seen particularly in agents that exhibit high muscarinic M3 and histamine H1 receptor blockade. The effect on glucose metabolism is seen the most with agents such as clozapine, olanzapine, and haloperidol and the least with agents such as ziprasidone.
Management tip: Given the ongoing change in the understanding of increases in weight and their association with the risk of developing type 2 diabetes, a metabolically safer approach involves starting with medications that have a lower propensity for weight gain, and the partial agonists/third-generation antipsychotics as a family presently have the best overall data.
Thiazide Diuretics
Thiazide diuretics are commonly used for the management of hypertension and are associated with metabolic complications including hypokalemia; higher cholesterol, triglycerides, and other circulating lipids; and elevated glucose. It’s thought that the reduced potassium level occurring as a result of these medications might contribute to new-onset diabetes. The hypokalemia occurring from these medications is thought to lead to a decrease in insulin secretion and sensitivity, which is dose dependent. Studies show that the number needed to harm for chlorthalidone-induced diabetes is 29 over 1 year. There is believed to be no additional risk beyond 1 year.
Management tip: It’s important to monitor potassium levels for those initiated on thiazide diuretics. If hypokalemia occurs, it would be pertinent to correct the hypokalemia with potassium supplements to mitigate the risk for new-onset diabetes.
Statin Therapy
Statin therapy is thought to be associated with decreased insulin sensitivity and impairment in insulin secretion. The overall incidence of diabetes is pegged to be between 9% and 12% on statin therapy on the basis of meta-analysis studies, and higher on the basis of population-based studies. Overall, the estimated number needed to harm is: 1 out of every 255 patients on statin therapy for 4 years may develop new-onset diabetes. Compare this with the extremely strong evidence for number needed to treat being 39 for 5 years with statin therapy in patients with preexisting heart disease to prevent one occurrence of a nonfatal myocardial infarction.
Management tip: Although statins are associated with a small incident increase in the risk of developing diabetes, the potential benefits of using statin therapy for both primary and secondary prevention of cardiovascular disease significantly outweigh any of the potential risks associated with hyperglycemia. This is an important discussion to have with patients who are reluctant to use statin therapy because of the potential risk for new-onset diabetes as a side effect.
Beta-Blockers
Beta-blockers are another commonly used group of medications for managing hypertension, heart failure, coronary artery disease, and arrhythmia. Nonvasodilating beta-blockers such as metoprolol and atenolol are more likely to be associated with increases in A1c, mean plasma glucose, body weight, and triglycerides compared with vasodilating beta-blockers such as carvedilol, nebivolol, and labetalol (Bakris GL et al; Giugliano D et al). Similarly, studies have also shown that atenolol and metoprolol are associated with increased odds of hypoglycemia compared with carvedilol. People on beta-blockers may have masking of some of the symptoms of hypoglycemia, such as tremor, irritability, and palpitations, while other symptoms such as diaphoresis may remain unaffected on beta-blockers.
Management tip: Education on recognizing and managing hypoglycemia would be important when starting patients on beta-blockers if they are on preexisting insulin/sulfonylurea therapy. Use of CGM devices may be helpful if there is a high risk for hypoglycemia, especially as symptoms of hypoglycemia are often masked.
Honorable Mention
Several other medications — including antiretroviral therapy, tyrosine kinase inhibitors, mechanistic target of rapamycin (mTOR) inhibitors, immunosuppressants, and interferon alpha — are associated with worsening glycemic control and new-onset diabetes. Consider these agents’ effects on blood glucose, especially in people with an elevated risk of developing diabetes or those with preexisting diabetes, when prescribing.
A special mention should also be made of androgen deprivation therapy. These include treatment options like goserelin and leuprolide, which are gonadotropin-releasing hormone (GnRH) agonist therapies and are commonly used for prostate cancer management. Depending on the patient, these agents may be used for prolonged duration. Androgen deprivation therapy, by definition, decreases testosterone levels in men, thereby leading to worsening insulin resistance. Increase in fat mass and concomitant muscle wasting have been associated with the use of these medications; these, in turn, lead to peripheral insulin resistance. Nearly 1 out of every 5 men treated with long-term androgen deprivation therapy may be prone to developing worsening of A1c by 1% or more.
Management tip: Men on androgen deprivation therapy should be encouraged to participate in regular physical activity to reduce the burden of insulin resistance and to promote cardiovascular health.
Drug-induced diabetes is potentially reversible in many cases. Similarly, worsening of glycemic control due to medications in people with preexisting diabetes may also attenuate once the effect of the drug wears off. Blood glucose should be monitored on an ongoing basis so that diabetes medications can be adjusted. For some individuals, however, the worsening of glycemic status may be more chronic and may require long-term use of antihyperglycemic agents, especially if the benefits of continuation of the medication leading to hyperglycemia far exceed any potential risks.
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