There are three varieties of basal insulin currently available: NPH insulin (Humulin N, Novolin N), insulin glargine (Lantus), and insulin detemir (Levemir). NPH is usually taken two or three times daily. It typically works in the body for 10–12 hours and has a “peak” of intensified action about 4–6 hours after it is injected. Because of this peak, injections of NPH must be timed carefully with respect to meals and exercise to avoid hypoglycemia.
Insulin glargine (Lantus) and insulin detemir (Levemir) are usually taken once daily, although some people do require two injections per day. They stay at a near-constant level within the blood circulation for approximately 24 hours and have little if any peak. Consequently, glargine and detemir can pose a lower risk of hypoglycemia than NPH. However, NPH is considerably cheaper than glargine or detemir.
Common side effects of insulin include injection site discomfort, hypoglycemia, and weight gain. With proper use, however, these risks can be minimized or even avoided entirely.
Intensive insulin therapy
Intensive insulin therapy refers to the use of basal and mealtime insulins together. Regular insulin (Humulin R, Novolin R) has been on the market longer than any other mealtime insulin currently available. Regular insulin is usually taken before each meal, 30–45 minutes prior to eating. Many people are quite satisfied with Regular insulin, but others find that remembering to take an injection 30–45 minutes before a meal can be difficult, or that it is hard to time injections correctly to avoid either a blood glucose spike or hypoglycemia. For these people, a “rapid-acting” insulin may be best; these insulins can be taken about 15 minutes before, or even immediately prior to, eating. Rapid-acting insulins currently on the market include insulin aspart (NovoLog), insulin lispro (Humalog), and insulin glulisine (Apidra). While more convenient, these insulins are considerably more expensive than Regular insulin.
Most insulin products sold today come in a variety of forms, including vials, prefilled insulin pens, and prefilled cartridges for use in insulin pens. Premixed insulin products containing both a basal and a shorter-acting insulin are also available.
Compared with other drugs used to treat Type 2 diabetes, insulin has the greatest ability to lower blood glucose and HbA1c — unlike most drugs, doses of insulin can usually be increased (or decreased) to whatever level is needed to achieve desired results. This should only be done, of course, under the guidance of a qualified health-care provider.
Often referred to as the “glitazones,” thiazolidinediones include both pioglitazone (Actos) and rosiglitazone (Avandia). These drugs are taken by mouth and work by reducing insulin resistance. Pioglitazone is considered to be a Tier 2, or less well-validated, therapy for Type 2 diabetes. Because of concerns that rosiglitazone may increase the risk of heart attack, its use is restricted in the United States. Pioglitazone, on the other hand, does not have any special restrictions on its use.
Thiazolidinediones can lower HbA1c by 1% to 2% but may take up to 12 weeks to reach their full blood-glucose-lowering potential. Common side effects of these drugs include weight gain and fluid retention. Because the risk of fluid retention is already high in people with heart failure, thiazolidinediones should not be taken by this population.
GLP-1 receptor agonists
This class of drugs is relatively new, with its first member, exenatide (Byetta), becoming available in the United States in 2005. The other drug in this class is liraglutide (Victoza), which was approved in 2010. Both drugs work by mimicking the actions of a natural hormone produced in the body called glucagon-like peptide-1 (GLP-1). They help lower blood glucose by telling the pancreas to produce more insulin following a meal and by decreasing production of another hormone — glucagons — that signals the liver to release glucose.