Background: In diabetes mellitus, the clinical goal of intensive glycemic control (lowering blood glucose concentrations to normal or near-normal levels) has been hindered by the lack of insulin regimens that duplicate the basal-bolus secretion of insulin by the healthy pancreas. In particular, intensive therapy has been associated with a risk of hypoglycemia. Objective: This article reviews the pharmacology, pharmacokinetics, dosing guidelines, adverse effects, and potential drug interactions of insulin glargine, a new long-acting recombinant human insulin analogue, Results of clinical trials of its efficacy and tolerability as a basal insulin in the treatment of type 1 and type 2 diabetes are summarized. Methods: Primary research and review articles on insulin glargine were identified through a search of MEDLINE from 1966 to July 2001. Abstracts were identified through a search of the Institute for Scientific Information Web of Science from 1995 to July 2001 and proceedings of American Diabetes Association scientific meetings. Additional information was obtained from the product information for insulin glargine, All identified articles and abstracts were evaluated for relevance, and all relevant information was included in the review. Priority was given to data from the primary medical literature. Results: Insulin glargine has a slower onset of action than human neutral protamine Hagedorn (NPH) insulin, a longer duration of action (up to 24 hours ), and no pronounced peak. It has similar tolerability and produces similar glycemic control to once- or twice-daily human NPH insulin, with a similar glucose-lowering effect on a molar basis. A decreased incidence of hypoglycemia, particularly at night, has been reported with insulin glargine compared with human NPH insulin. Insulin glargine appears' to be comparable to human NPH insulin in terms of toxicity, adverse effects, immunogenicity, and potential for drug interactions. Results of clinical trials of insulin glargine in both type 1 and type 2 diabetes support its use in combination with a short-acting insulin, insulin lispro, or oral antidiabetic medications. Although insulin glargine cannot be mixed with other insulin preparations, it has the potential convenience of providing basal insulin with once-daily bedtime dosing. Conclusions: Based on the as yet small amount or data from full clinical study reports in peer-reviewed publications, insulin glargine appears to be a well-tolerated and effective basal insulin preparation for patients with type 1 or type 2 diabetes (including pediatric patients). Its delayed onset of action and prolonged, flat time-action profile mimic the action of endogenous basal insulin (or an insulin pump), decreasing the risk of hypoglycemic episodes. Insulin glargine may be a useful new option for meeting overnight insulin requirements, although most patients will require a rapid-acting insulin such as insulin lispro with or before meals for optimal management of blood glucose levels.
