Rx Update: September 2001
Mary Ross, R.Ph., M.B.A.
Peer Review Status: Internally Reviewed
Insulin glargine is an acidic solution which microprecipitates after subcutaneous administration forming crystals in the subcutaneous tissue. The crystals dissolve slowly releasing insulin into the bloodstream. The onset of action of insulin glargine is 1 hour following subcutaneous administration. Full activity is reached within 4 to 5 hours and persists at a constant level for 24 hours. In contrast to isophane (NPH) and insulin zinc suspension (Lente®) insulins, no significant insulin peaks occur with insulin glargine.
The adverse effects of insulin glargine are similar to those of NPH insulin and include allergic reactions, injection site reactions, lipodystrophy, pruritus, rash, and hypoglycemia. Insulin glargine causes more pain at the injection site that NPH insulin (2.7% vs. 0.7%). The incidence of hypoglycemia is similar to or slightly lower than NPH insulin, although insulin glargine may be associated with less nocturnal hypoglycemia than once daily NPH insulin.
Insulin glargine is administered as a subcutaneous injection once daily at bedtime. It should not be administered intravenously. Patients not currently taking insulin therapy can be initiated at a dose of 10 units once daily and titrated to the appropriate dose based on response. Patients currently taking once-daily NPH insulin or zinc insulin suspension (extended) (Ultralente®) can be initiated on insulin glargine at the same total daily dose. In patients taking NPH insulin twice-daily, the initial daily dose of insulin glargine should be reduced by 20% compared to the total daily dose of NPH insulin and then titrated based on response.
Insulin glargine should not be mixed/diluted with any other insulin or solution. The solution may become cloudy and the pharmacokinetic/pharmacodynamic profile of insulin glargine and the mixed insulin may be altered. Patients will need to administer separate injections of regular insulin or lispro insulin before meals since they cannot be mixed with insulin glargine and combination products are not available.
Insulin glargine is available as a 100 unit per ml injection in 5 and 10 ml vials. The company has not conducted any stability studies in syringes; therefore, each dose must be drawn up just prior administration. The vials should be stored under refrigeration. At room temperature, the 5 ml vial should be used within 14 days and the 10 ml vial within 28 days. If refrigerated, the 5 ml vial should be used within 28 days once it is opened.
There has been confusion reported between Lantus® (insulin glargine) and Lente® (zinc insulin suspension) insulins because of the look-a-like and sound-a-like names. It is imperative that nurses and pharmacists verify which insulin had been prescribed when either Lantus® or Lente® insulin has been ordered for a patient.