The Spiros insulin consists of a dry powder inhaler and blisterdisks. The blisterdisks contain a preparation of 11% micronized insulin crystals blended with lactose monohydrate NF. The blend is filled into blisterdisks at a target fill weight of 9.5 mg per well. This results in 1.05 mg of insulin in each blister well that is equivalent to 30 units. The median aerodynamic particle size of the insulin crystals is 2-3 ^m and the median size of the lactose particles is 150 ^m. The inhaler is a hand held breath activated device that delivers the dry powder crystals (Fig. 8). Inspiratory flow activates a battery-powered twin blade impeller that assisted in deagglomeration of the drug and carrier during inspiration (39).
In an open label euglycemic glucose clamp in healthy volunteers four doses of the Spiros system's (60, 90, 120, and 150 U) pharmacokinetics and glucodynamics were evaluated against those subjects receiving 2 of the 3 possible doses of SC regular insulin (8, 14, and 20 U). Serum insulin levels following inhalation of insulin peaked approximately 60 min earlier when compared to SC regular insulin (P <0.001). The time to maximum glucose infusion rate was reached approximately 70 min earlier with inhaled insulin than with SC regular insulin. The Spiros system intra- and intersubject variability were found to be comparable to that of SC regular insulin (39). Smokers have increased serum insulin levels; however they have reduced glucodynamic effect due to increased insulin resistance (40).
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