SELECTIVE DELIVERY OF INSULIN INTO THE BRAIN - INTRAOLFACTORY ABSORPTION

The distribution of insulin between blood and brain was investigated i n mice. The drug was administered subcutaneously and by instilling the drug to the olfactory region of the nasal cavity. The concentrations of insulin in the biological samples were measured by a gamma-counter. A significantly higher concentration of insulin was measured in the b rain, following intraolfactory administration compared to subcutaneous injection. The absorption was also found to be very rapid. Ten minute s after the administration the concentration in the brain had reached 193 counts/min per g (equivalent to 37 mu U insulin/g tissue), which w as 487% higher than achieved after subcutaneous injection. The majorit y (>99%) of the CNS drug development programmes are devoted solely to CNS drug discovery and less than 1% are devoted to drug delivery. The results suggest that it may be possible to achieve absorption directly into the brain, by-passing the blood-brain barrier. The olfactory reg ion may be the key for this absorption.