Improved delivery through biological membranes XX: Nicotinamide----dihydronicotinamide based ester-linked redox carrier systems.

The 1-carboxyalkyl nicotinamide----dihydronicotinamide redox pair is a new type of brain-enhanced chemical delivery system for drugs containing hydroxyl groups. The rate of oxidation of the dihydro carrier form and subsequent "lock-in" into the brain of the quaternary carrier-drug species, as well as the rate of the hydrolytic release of the drug, depend on both the length and branching of the alkyl chain separating the carrier ring system. Testosterone was used as a model drug, and it was successfully released in a sustained and enhanced manner to the brain in significantly higher concentrations than with the previously reported trigonelline----dihydrotrigonelline carrier system.