Alternate Routes of Insulin Delivery

The relative merits of intraperitoneal (i.p.) and subcutaneous (s.c.) insulin delivery compared with intravenous (i.v.) delivery were investigated in seven diabetic patients using a combination of glucosecontrolled closed-loop (Biostator) and portable open-loop (Siemens minipump) insulin infusion systems. With appropriate algorithms for feedback-controlled insulin infusion, it could be shown that each of the three approaches was able to achieve satisfactory blood glucose levels. After glucose challenge, i.p. administration required almost twice as much insulin and twice as much time as i.v. to return to normal blood glucose (BG) levels. When the insulin dosage profile determined with Biostator feedback control is transformed to a simpler program consisting of basal rate and rectangularly shaped supplementary profiles for the open-loop system, good control was achieved during observation periods of about 1 wk with both s.c. and i.p. delivery. Subcutaneous infusion with the minipump was also carried out for a period of 70 days in one patient on an outpatient basis. In this long-term study s.c. infusion was not superior to twice-daily s.c. injections with frequent monitoring of BG and self-adjustment of insulin dosage by the patient. The optimal method of delivery appeared to be i.v., with i.p. and s.c. in second and third place. Intraperitoneal delivery seems to be a viable alternative that might help to solve some problems in the development of implantable devices. Further investigations should be carried out.