Absorption kinetics of subcutaneously injected insulin. Evidence for degradation at the injection site.

The absorption of subcutaneously injected insulin was examined by injecting semisynthetic [3H] insulin in anaesthetized pigs and subsequently analysing the tissue excised from the injection site. Contrary to previously accepted views, a significant proportion of insulin was degraded at the injection site. The disappearance of intact [3H] insulin from the injection site followed a monoexponential function with a half-time of 59 min.