Anavex Life Sciences Corp (AVXL)

[OFP]

The ratio of donepezil to total radioactivity in brain was 86.9 to 93.0%, indicating low permeability of the metabolites through the blood-brain barrier.

F1ash already tried to explain this but I'll try again.

DZP with a radioactive tag was administered. As DZP is metabolized (broken down by usual metabolic pathways) it breaks into its "metabolites". Metabolites are not DZP they are break down products and afaik are clinically inactive. That break down occurs outside the brain and the metabolites (which are not outside the brain) have low permeability to get back in to the brain. Because of this 86.9-93.0% of the total radioactivity in the brain is intact DZP. In other words, the vast majority of the radioactivity in the brain is DZP because the metabolites can not get back in.

DZP has no trouble getting into the brain. It is actively transported. https://www.ncbi.nlm.nih.gov/pubmed/19691109