Continuous subcutaneous insulin infusion: comparison of plasma insulin profiles after infusion or bolus injection of the mealtime dose.

To help optimize meal-time blood glucose control in diabetic patients by continuous subcutaneous insulin infusion we have studied plasma insulin profiles in six normal subjects, suppressing endogenous insulin secretion with somatostatin. Insulin was administered subcutaneously either as a bolus or by high-rate infusion. Mean infusion profiles were similar on the two occasions, with peak levels at 75 and 90 min respectively, and a linear decline to 34% and 36% of peak concentrations at 5 h. Bolus injection resulted in a faster rise in insulin concentration, more consistent with physiological requirements. It is concluded that bolus delivery would be similar in effect while mechanically simpler to achieve than infusion, when part of a dual rate subcutaneous infusion system. The dose should be given 30 min before meals, if peak insulin concentrations are to be coincident with those found physiologically. Insulin concentrations remain high in the post-absorptive phase.