Ketosis-Prone Type 2 Diabetes Medication
- Author: Richard S Krause, MD; Chief Editor: George T Griffing, MD more...
Insulin injected subcutaneously is the first-line treatment of type 1 diabetes mellitus. The different types of insulin vary with respect to onset and duration of action. Short-, intermediate-, and long-acting insulins are available. Short-acting and rapid-acting insulins are the only types that can be administered intravenously (IV). Human insulin currently is the only species of insulin available in the United States; it is less antigenic than the previously used animal-derived varieties.
Pharmacologic therapy of type 2 diabetes has changed dramatically in the last 10 years, with new drugs and drug classes becoming available. These drugs allow for the use of combination oral therapy, often with improvement in glycemic control that was previously beyond the reach of medical therapy.
Agents used in diabetic therapy include the following:
Glucagonlike peptide–1 (GLP-1) agonists
Dipeptidyl peptidase IV (DPP-4) Inhibitors
Bile acid sequestrants
Traditionally, diet modification has been the cornerstone of diabetes management. Weight loss is more likely to control glycemia in patients with recent onset of the disease than in patients who are significantly insulinopenic. Medications that induce weight loss, such as orlistat, may be effective in highly selected patients but are not generally indicated in the treatment of the average patient with type 2 diabetes mellitus.
Patients who are symptomatic at initial presentation with diabetes may require transient treatment with insulin to reduce glucose toxicity (which may reduce beta-cell insulin secretion and worsen insulin resistance) or an insulin secretagogue to rapidly relieve symptoms such as polyuria and polydipsia.
Rapid-acting insulins are used whenever a rapid onset and short duration are appropriate (eg, before meals or when the blood glucose level exceeds target and a correction dose is needed). Rapid-acting insulins are associated with less hypoglycemia than regular insulin.
Currently, short-acting insulins are less commonly used than the rapid-acting insulins in patients with type 1 DM. They are used when a slightly slower onset of action or a greater duration of action is desired.
Intermediate-acting insulins have a relatively slow onset of action and a relatively long duration of action. They are usually combined with faster-acting insulins to maximize the benefits of a single injection.
Long-acting insulins have a very long duration of action and, when combined with faster-acting insulins, provide better glucose control for some patients. In patients with type 1 DM, they must be used in conjunction with a rapid-acting or short-acting insulin given before meals.
Premixed insulins contain a fixed ratio of rapid-acting insulins with longer-acting insulin, which can restrict their use. Premixed insulin is usually not recommended in type 1 DM patients, because of their need for frequent adjustments of premeal insulin doses.
Insulin aspart has a rapid onset of action, 5-15 minutes. The peak effect occurs within 30-90 minutes, and the usual duration of action is 2-4 hours. Insulin aspart is approved by the US Food and Drug Administration (FDA) for use in insulin pumps.
Insulin glulisine has a rapid onset of action, 5-15 minutes. The peak effect occurs within 30-90 minutes, and the usual duration of action is 2-4 hours. Insulin glulisine is FDA-approved for use in insulin pumps.
Insulin lispro has a rapid onset of action, 5-15 minutes. The peak effect occurs within 30-90 minutes, and the usual duration of action is 2-4 hours.
Regular insulin has a short onset of action, 0.5 hour. Its peak effect occurs within 2-4 hours, and its usual duration of action is 5-8 hours. Preparations that contain a mixture of 70% neutral protamine Hagedorn (NPH) insulin and 30% regular human insulin (eg, Novolin 70/30 and Humulin 70/30) are available, but the fixed ratios of intermediate-acting to rapid-acting insulin may restrict their use.
Insulin detemir is indicated for once-daily or twice-daily subcutaneous administration in individuals with type 1 DM who require long-acting basal insulin for hyperglycemia control. Its duration of action ranges from 5.7 hours (low dose) to 23.2 hours (high dose). The prolonged action results from slow systemic absorption of detemir molecules from the injection site. Its primary activity is regulation of glucose metabolism.
Insulin detemir binds to insulin receptors and lowers blood glucose levels by facilitating cellular uptake of glucose into skeletal muscle and fat; it also inhibits glucose output from the liver. The drug inhibits lipolysis in adipocytes, inhibits proteolysis, and enhances protein synthesis.
Insulin glargine stimulates proper utilization of glucose by the cells and reduces blood sugar levels. It has no pronounced peaks of action, because a small amount of insulin is gradually released at a constant rate over 24 hours. A possible association of insulin glargine with an increased risk of cancer has been reported.
The combination of insulin aspart protamine with insulin aspart includes 30% rapid-onset insulin (ie, insulin aspart) and 70% intermediate-acting insulin (ie, insulin aspart protamine). Insulin aspart is absorbed more rapidly than regular human insulin, and insulin aspart protamine has a prolonged absorption profile after injection.
The combination of insulin lispro protamine with insulin lispro includes 75% insulin lispro protamine, which has a prolonged duration of action, and 25% insulin lispro, which is a rapid-onset insulin.
These agents are considered the first choice for oral type 2 diabetes treatment. They reduce hyperglycemia by decreasing hepatic gluconeogenesis (primary effect) and increasing peripheral insulin sensitivity (secondary effect). They do not increase insulin levels or cause weight gain. Alone, they rarely cause hypoglycemia.
Biguanides are absorbed from the intestines and are not bound to plasma proteins. They are not metabolized and are rapidly eliminated by the kidneys. Drug levels increase markedly in renal insufficiency. Lactic acidosis is a rare, but serious, complication that may occur with drug accumulation.
Metformin is used as monotherapy or in combination with sulfonylureas, thiazolidinediones, or insulin. It is taken with food to minimize adverse GI effects. Metformin is available in immediate-release and extended-release formulations, as well as in combination with other antidiabetic drugs.
Metformin is contraindicated in patients with impaired renal function, as indicated by a serum creatinine level of greater than 1.5 mg/dL in men or of more than 1.4 mg/dL in women, or an estimated GFR of less than 60 mL/min. It also should not be used within 48 hours of IV iodinated contrast medium.
These amylinomimetic agents elicit endogenous amylin effects by delaying gastric emptying, decreasing postprandial glucagon release, and modulating appetite.
Pramlintide acetate is a synthetic analogue of human amylin, a naturally occurring hormone made in pancreatic beta cells that is deficient in people with type 1 DM. It slows gastric emptying, suppresses postprandial glucagon secretion, and regulates food intake through centrally mediated appetite modulation.
Sulfonylureas are time-honored insulin secretagogues (ie, oral hypoglycemic agents). They have been used as monotherapy and in combination with other oral hypoglycemic agents or with insulin, although glimepiride is the only sulfonylurea approved by the FDA for combination therapy. Sulfonylureas function by stimulating the release of insulin from pancreatic beta cells and can usually reduce HbA1c by 1-2% and blood glucose concentrations by about 20%.
Glyburide is a second-generation sulfonylurea. It is more potent and exhibits fewer drug interactions than first-generation agents. It also has a longer half-life than most sulfonylureas. Glyburide has been used as an alternative to insulin for the treatment of gestational diabetes, although it is not FDA approved for this indication. Glyburide (known as glibenclamide in the United Kingdom) was one of the sulfonylureas used in the United Kingdom Prospective Diabetes Study (UKPDS).
Glipizide is also a second-generation sulfonylurea. It is more potent and exhibits fewer drug interactions than first-generation agents. It may cause more physiologic insulin release with less risk for hypoglycemia and weight gain than other sulfonylureas.
Pancreatic alpha cells of the islets of Langerhans produce glucagon, a polypeptide hormone. Glucagon increases blood glucose levels by promoting hepatic glycogenolysis and gluconeogenesis.
Glucagon elevates blood glucose levels by inhibiting glycogen synthesis and enhancing the formation of glucose from noncarbohydrate sources such as proteins and fats (gluconeogenesis). It increases hydrolysis of glycogen to glucose in the liver and accelerates hepatic glycogenolysis and lipolysis in adipose tissue. Glucagon also increases the force of contraction in the heart and has a relaxant effect on the gastrointestinal tract.
Antidiabetics, Meglitinide Derivatives
Meglitinides are much more short-acting insulin secretagogues than sulfonylureas. Preprandial dosing potentially achieves more physiologic insulin release and less risk for hypoglycemia. Meglitinide monotherapy has efficacy similar to that of sulfonylureas.
Repaglinide is probably most useful in patients at increased risk for hypoglycemia who still need an insulin secretagogue. It works by stimulating insulin release from pancreatic beta cells. Better control of postprandial glycemic excursions also may be achieved with repaglinide. It is FDA approved for monotherapy and for combination therapy with metformin or thiazolidinediones.
Nateglinide mimics endogenous insulin patterns, restores early insulin secretion, and controls mealtime glucose surges. It works by stimulating insulin release from pancreatic beta cells. It is indicated as monotherapy for type 2 diabetes or as combination therapy with metformin or a thiazolidinedione. Nateglinide is available in 60-mg and 120-mg tablets.
Antidiabetics, Alpha-Glucosidase Inhibitors
Alpha-glucosidase inhibitors prolong the absorption of carbohydrates and thus help to prevent postprandial glucose surges. Their induction of flatulence greatly limits their use. Doses of these agents should be titrated slowly to reduce GI intolerance. Their effect on glycemic control is modest, affecting primarily postprandial glycemic excursions.
Miglitol is not absorbed, so liver function abnormalities do not occur. It is FDA approved for use as monotherapy or in combination with sulfonylureas. Its modest effect on glycemia and high degree of GI adverse effects (flatulence) limit its use.
Acarbose was the first alpha-glucosidase inhibitor approved by the FDA. It is absorbed to a small degree, so liver function abnormalities can occur rarely. It can be used as monotherapy or in combination with other treatment modalities. The modest effect of acarbose on glycemia and its high degree of GI adverse effects (flatulence) limit its use.
Thiazolidinediones are a newer class of drugs that reduce insulin resistance in the periphery (ie, they sensitize muscle and fat to the actions of insulin) and perhaps to a small degree in the liver (ie, insulin sensitizers, antihyperglycemics). They activate peroxisome proliferator–activated receptor (PPAR) gamma, a nuclear transcription factor that is important in fat cell differentiation and fatty acid metabolism. The major action of thiazolidinediones is probably actually fat redistribution. These drugs may have beta-cell preservation properties.
Thiazolidinediones have moderate glycemic efficacy, between that of alpha-glucosidase inhibitors and sulfonylureas. They are the most expensive oral agents.
Pioglitazone is indicated as an adjunct to diet and exercise to improve glycemic control. It improves target-cell response to insulin without increasing insulin secretion from the pancreas. It also increases insulin-dependent glucose use in skeletal muscle and adipose tissue. Pioglitazone lowers triglycerides more than rosiglitazone, probably because of its PPAR-alpha effect.
Long duration of pioglitazone use and high cumulative doses have been linked with slightly increased risk for bladder cancer. The FDA currently recommends not prescribing pioglitazone for patients with active bladder cancer and using it with caution in patients with a history of bladder cancer.
Rosiglitazone is an insulin sensitizer with a major effect on the stimulation of glucose uptake in skeletal muscle and adipose tissue. It lowers plasma insulin levels. It is indicated for type 2 diabetes associated with insulin resistance, as monotherapy and in conjunction with sulfonylureas and/or metformin and insulin. It may preserve beta-cell function and yields positive effects on vasculature and inflammation. It changes LDL and HDL particle size.
Because of data suggesting an elevated risk of myocardial infarction in patients treated with rosiglitazone, this agent is currently available only via a restricted access program. Patients currently taking rosiglitazone and benefiting from the drug are permitted to continue using it if they choose to do so. Rosiglitazone is available to new patients only if they are unable to achieve glucose control on other medications and are not willing to take pioglitazone, the only other thiazolidinedione.
As of November 18, 2011, rosiglitazone was no longer available in retail pharmacies. It can be purchased only through specially certified pharmacies participating in the Avandia-Rosiglitazone Medicines Access Program.
Antidiabetics, Glucagonlike Peptide-1 Agonists
Glucagonlike peptide–1 (GLP-1) agonists have a novel mechanism of action: they mimic the endogenous incretin GLP-1, stimulating glucose-dependent insulin release (as opposed to oral insulin secretagogues, which may cause non–glucose-dependent insulin release and hypoglycemia), reducing glucagon, and slowing gastric emptying.
Exenatide injectable solution (Byetta)
Exenatide is a GLP-1 agonist that improves glycemic control in patients with type 2 diabetes mellitus. Like endogenous incretins, it enhances glucose-dependent insulin secretion by pancreatic beta cells, suppresses inappropriately elevated glucagon secretion, and slows gastric emptying. The drug's 39–amino acid sequence partially overlaps that of the human incretin GLP-1.
Exenatide is indicated as adjunctive therapy to improve glycemic control in patients with type 2 diabetes who have not achieved glycemic control with metformin or a sulfonylurea. The solution is administered by subcutaneous injection twice daily.
This formulation of exenatide allows once-weekly dosing by subcutaneous injection. Glycemic control attained with once-weekly long-acting exenatide injections may be superior to that achieved with the twice-daily injections.
Liraglutide is a once-daily injectable GLP-1 receptor agonist that stimulates G-protein in pancreatic beta cells. It increases intracellular cyclic adenosine monophosphate (cAMP), leading to insulin release in the presence of elevated glucose concentrations. Liraglutide is indicated as an adjunct to diet and exercise to improve glycemic control in adults with type 2 diabetes mellitus. The drug has not been studied in combination with insulin.
Liraglutide is not recommended as first-line pharmacologic therapy, because of potential serious adverse effects. Liraglutide is contraindicated in patients with a history or family history of medullary thyroid carcinoma or multiple endocrine neoplasia syndrome type 2, as dose- and duration-dependent thyroid C-cell tumors have occurred in animal studies of liraglutide.
In addition, clinical studies suggest that liraglutide may cause pancreatitis, although conclusive evidence has not been established. Nevertheless, patients should be monitored for unexplained, persistent, severe abdominal pain, with or without vomiting, and liraglutide should be discontinued if pancreatitis is suspected.
Antidiabetics, Dipeptidyl Peptidase IV Inhibitors
Incretin hormones are part of an endogenous system involved in the physiologic regulation of glucose homeostasis. They increase insulin release and decrease glucagon levels in the circulation in a glucose-dependent manner. DPP-4 degrades numerous biologically active peptides, including the endogenous incretins GLP-1 and glucose-dependent insulinotropic peptide (GIP). DPP-4 inhibitors prolong the action of incretin hormones.
The FDA has approved 3 oral DDP-4 inhibitors: sitagliptin, saxagliptin, and linagliptin. A fourth, vildagliptin, is currently under FDA review.
Sitagliptin demonstrates selectivity for DPP-4 and does not inhibit DPP-8 or DPP-9 activity in vitro at concentrations approximating those from therapeutic doses. Sitagliptin can be used as a monotherapy or in combination with metformin or a thiazolidinedione. It is given once daily and is weight neutral.
Saxagliptin inhibits DPP-4 and thereby increases concentrations of GLP-1 and GIP, which stimulate insulin release in response to increased blood glucose levels following meals. This action enhances glycemic control. Saxagliptin is indicated as an adjunct to diet and exercise to improve glycemic control in adults with type 2 diabetes mellitus.
Linagliptin is a DPP-4 inhibitor that increases and prolongs incretin hormone activity. It is indicated for adults with type 2 diabetes mellitus, along with diet and exercise, to lower blood glucose levels. It may be used as monotherapy or in combination with other common antidiabetic medications, including metformin, sulfonylurea, or pioglitazone; it has not been studied in combination with insulin.
Bile Acid Sequestrants
Colesevelam is FDA approved as an adjunctive therapy to improve glycemic control in adults with type 2 diabetes mellitus.
Colesevelam is a high-capacity bile acid sequestrant. It is indicated as an adjunct to diet and exercise to improve glycemic control in adults with type 2 diabetes mellitus. The precise mechanism by which colesevelam improves glycemic control is largely unknown.
Antidiabetics, Intermediate-Acting Insulins
Intermediate-acting insulins have a slow onset of action and a longer duration of action. These agents are commonly combined with faster-acting insulins to maximize the benefits of a single injection.
Insulin neutral protamine Hagedorn (NPH) has an onset of action of 3-4 hours. The peak effect occurs within 8-14 hours, and its usual duration of action is 16-24 hours. The drug appears cloudy and must be gently mixed and checked for clumping; if clumping occurs, the insulin should be discarded.
Antiparkinson Agents, Dopamine Agonists
Quick-release bromocriptine acts on circadian neuronal activities within the hypothalamus to reset the abnormally elevated hypothalamic drive for increased plasma glucose, triglyceride, and free fatty acid levels in fasting and postprandial states in patients with insulin resistance.
This quick- release formulation is the only bromocriptine product indicated for type 2 diabetes mellitus. It is indicated as an adjunct to diet and exercise to improve glycemic control.
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