For the purpose of administrating insulin rectally, an insulin suppository was prepared by pestling porcine crystalline insulin with corn oil and surfactant (polyoxyethylene-9-laurylether). The final concentrations of insulin and surfactant were set at 10-50 U/kg and 2-4 w/w%, respectively.
In normal dogs, a significant increase in mean plasma immunoreactive insulin concentration (IRI) (64, 88, 115μU/ml) was observed at 15 min after administration of the insulin suppository (2, 3 and 5 U/kg body weight, respectively), followed by a significant decrease in plasma glucose level (36, 38, 56%, respectively).
Following suppository administration to depancreatized dogs at a dose of 5 U/kg, the mean peak IRI was 167μU/ml at 30 min, which was significantly higher than that in normal dogs (p<0.05, n=5).
The main features of the insulin suppository so prepared were: 1) even at a dose of 2 U/kg by rectal administration, a marked increase in IRI was observed, and 2) insulin was absorbed more rapidly from the rectum than when injected intramuscularly.
It was also shown that insulin is absorbed from the rectum to a greater extent in severe diabetic dogs than in normal dogs.
