No pharmacokinetic effect of retaining the infusion site up to four days during continuous subcutaneous insulin infusion therapy

This study was designed to investigate whether the indwelling time of the needle during continuous subcutaneous insulin infusion (CSII) could contribute to one of the main problems with subcutaneous insulin administration, that is the day-to-day intra-patient variation in absorption. The effect on insulin kinetics after a bolus dose was investigated at different time intervals up to 4 days after insertion of an indwelling catheter in situ for CSII therapy. Nine insulin-dependent diabetic patients treated with pump (Nordisk Infuser; Velosulin 100 U ml-1) took part in the study. The evening before day 1 of the investigation a needle connected to the pump with a polyethylene catheter was inserted subcutaneously on the abdominal wall where it remained throughout the investigation. There were no significant differences in blood glucose or plasma free insulin profiles between days 1, 3, and 5. The intra-patient coefficient of variation of free insulin was 38% at basal and 19% at post-bolus state. We conclude that during CSII it is acceptable from a pharmacokinetic point of view to retain the infusion site for up to 4 days.