Abstract
The possibility of insulin being enzymatically degraded in contact with the nasal mucosa has been studied in vitro. The insulin concentration was followed during 3 h incubation at 37°C with freshly collected human nasal wash, isolated enzymes from pig and rabbit nasal mucosal tissue, leucine aminopeptidase and microsomal aminopeptidaes, respectively. The rate of defradation with human nasal wash was found to be ≤ 0.02 μg/min, which indicates that less than 0.5% of an intranasally applied insulin dose may be destroyed by local enzymes during the time of absorption. The observed degradation was not found to be limiting for an intranasal application of insulin.
