Insulin absorption is faster when keeping the infusion site in use for three days during continuous subcutaneous insulin infusion.

To evaluate the possible influence of regular infusion site changes on insulin absorption, fifteen type 1 diabetic patients using continuous subcutaneous insulin infusion (CSII) were studied on four occasions: the first day after an infusion site was settled, again the first day after a new infusion site was utilized and the two fourth days after the two infusion sites had been used for three days. A bolus of insulin (1 U/10 kg of body weight) was infused by the pump in the lower para-umbilical region. Plasma free insulin and blood glucose levels were determined before and during 240 min of the study at 30-min intervals. It was found that the peak times extracted from the individual insulin curves were shorter in 17 out of 23 curves when the fourth day was compared with the first day and the mean value of peak time of the fourth day was significantly shorter than that of the first day (56 +/- 11 vs 110 +/- 15 min, P less than 0.01). The mean area under the insulin curves during the first hour of the study tended to increase on the fourth day compared to that of the first day (25 +/- 2.2 vs 21 +/- 2.1 mU.l-1.min, P = 0.12). The decremental area of blood glucose on the fourth day was larger than on the first day (405 +/- 111 vs 82 +/- 160 mmol.l-1.min, P less than 0.05). We conclude that during CSII, the absorption rate of the injected insulin bolus is faster when the infusion site has been in use continuously for three days.