Nasal administration of a cognition enhancer provides improved bioavailability but not enhanced brain delivery

Compound 1 [3,3-bis(4-pyridylmethyl)-1-phenylindolin-2-one] is an experimental cognition-enhancing drug now being developed for cognitive disorders. Oral bioavailability of 1 in rats was less than 10% of the dose. Nasal dosing improved bioavailability to greater than 50%. Brain levels of total radioactivity were measured after iv and nasal doses of radiolabeled 1. The ratio of AUCbrain:AUCplasma was the same by both routes, so nasal dosing did not enhance brain delivery. This is in contrast to other reports of large molecular weight substances and metals gaining direct access to the brain through the nasal epithelium.