Insulin therapy for type 2 diabetes: rescue, augmentation, and replacement of beta-cell function.

Type 2 diabetes is characterized by progressive beta-cell failure. Indications for exogenous insulin therapy in patients with this condition include acute illness or surgery, pregnancy, glucose toxicity, contraindications to or failure to achieve goals with oral antidiabetic medications, and a need for flexible therapy. Augmentation therapy with basal insulin is useful if some beta-cell function remains. Replacement therapy with basal-bolus insulin is required for beta-cell exhaustion. Rescue therapy using replacement regimens for several weeks may reverse glucose toxicity. Replacement insulin therapy should mimic normal release patterns. Basal insulin, using long-acting insulins (i.e., neutral protamine Hagedorn [NPH], ultralente, glargine) is injected once or twice a day and continued on sick days. Bolus (or mealtime) insulin, using short-acting or rapid-acting insulins (i.e., regular, aspart, lispro) covers mealtime carbohydrates and corrects the current glucose level. The starting dose of 0.15 units per kg per day for augmentation or 0.5 units per kg per day for replacement can be increased several times as needed. About 50 to 60 percent of the total daily insulin requirement should be a basal type, and 40 to 50 percent should be a bolus type. The mealtime dose is the sum of the corrective dose plus the anticipated requirements for the meal and exercise. Adjustments should be made systematically, starting with the fasting, then the preprandial and, finally, the postprandial glucose levels. Basal therapy with glargine insulin provides similar to lower A1C levels with less hypoglycemia than NPH insulin. Insulin aspart and insulin lispro provide similar A1C levels and quality of life, but lower postprandial glucose levels than regular insulin.