Technological problems of miniaturized insulin dosing devices and some approaches to clinical trials.

With the long-term goal of developing implantable insulin dosing devices, we have since 1971 developed various types of programme-controlled units for clinical research. In the initial stage, a 24-hour, fixed-programme bed-side device has been in clinical use since 1973. The good results with even labile diabetics has supplied the basis for the further development of sensorless units. Via intermediate stages, two types of miniaturized portable devices were constructed: fixed-programme and demand-programme devices. The essential equipment components have been optimized with a view to later implantability: hermetically sealed capsule for the dosing device, refilling membrane for the insulin reservoir, bubble-free drawing off of the insulin via a wick from a collapsible silicone reservoir, the stepping motor-driven roller pump of approx. 9 cm3 volume, an energy consumption of about 50 mu W, and electronic safety and alarm circuits. Because of stability problems of the insulin, the neutral insulin U-1000 used initially was changed to acid insulin U-100 (both from Hoechst).