Insulin glargine is a recombinant human insulin analogue produced by DNA technology using a nonpathogenic strain of Escherichia coli. Two modifications of human insulin result in a stable molecule which is soluble in slightly acidic conditions (pH 4.0) and precipitates in the neutral pH of subcutaneous tissue. Because of these properties, absorption of insulin glargine is delayed and the analogue provides a fairly constant, basal insulin supply without peaks in plasma insulin levels for approximately 24 hours, similar to that achieved by a continuous subcutaneous insulin infusion. Insulin glargine is indicated as a once daily subcutaneous injection to provide basal glycaemic control in adults and children aged >6 years with type 1 diabetes mellitus and in adults with type 2 diabetes mellitus. Fasting plasma glucose and fasting blood glucose levels generally improved to a greater extent in patients with type 1 diabetes mellitus receiving insulin glargine than patients who administered Neutral Protamine Hagedorn (NPH) insulin. In patients with type 1 or 2 disease, glycosylated haemoglobin levels were slightly reduced and to a similar extent with insulin glargine and NPH insulin. Most clinical trials in patients with type 1 or 2 diabetes mellitus demonstrated a lower incidence of hypoglycaemia, especially nocturnal hypoglycaemia, compared with NPH insulin. One of the most common adverse events with insulin glargine treatment was injection site pain which, in some studies, occurred more frequently than in patients receiving NPH insulin. In all cases the symptoms were mild and treatment discontinuation was not required. Otherwise, the drug is well tolerated and does not appear to be immunogenic.
Conclusions: Insulin glargine once a day provides basal control of glycaemia for approximately 24 hours without inducing peaks in plasma insulin levels in patients with type 1 or 2 diabetes mellitus. In long term, well designed trials insulin glargine once daily improved glycaemic control at least as effectively as NPH insulin given once or twice daily. The drug was well tolerated and in most studies the incidence of nocturnal hypoglycaemia was significantly less in patients treated with insulin glargine compared with patients receiving NPH insulin. Therefore, insulin glargine is likely to be a useful addition to the armamentarium of insulin therapy by establishing basal glycaemic control with once daily administration and a reduced risk of nocturnal hypoglycaemia.