Insulin Bolus Administration in Insulin Pump Therapy: Effect of Bolus Delivery Speed on Insulin Absorption from Subcutaneous Tissue

Background: This study assessed subcutaneous absorption kinetics of rapid-acting insulin administered as a bolus using bolus delivery speeds commonly employed in commercially available insulin pumps (i.e., 2 and 40 s for delivering 1 insulin unit). Materials and Methods: Twenty C-peptide-negative type 1 diabetic subjects were studied on two occasions, separated by at least 7 days, using the euglycemic clamp procedure. After an overnight fast, subjects were given, in random order, a subcutaneous insulin bolus (15 U of insulin lispro, Eli Lilly) either for 30 s using an Animas IR2020 pump (fast bolus delivery) or for 10 min using a Medtronic Minimed Paradigm 512 pump (slow bolus delivery). Results: Fast bolus delivery resulted in an earlier onset of insulin action as compared with slow bolus delivery (21.0 +/- 2.5 vs. 34.3 +/- 2.7 min; P < 0.002). Furthermore, time to reach maximum insulin effect was found to be 27 min earlier with fast bolus delivery as compared with slow bolus delivery (98 +/- 11 vs. 125 +/- 16 min; P < 0.005). In addition, the area under the plasma insulin curve from 0 to 60 min for fast bolus delivery was greater than the one for slow bolus delivery (10,307 +/- 1291 vs. 8192 +/- 865 min center dot pmol/L; P = 0.027). Conclusions: Results suggest that insulin bolus delivery with fast delivery speed may result in more rapid insulin absorption and, thus, may provide a better control of meal-related glucose excursions than that obtained with bolus delivery using slow delivery speeds. Our findings may have important implications for the future design of the bolus delivery unit of insulin pumps.