Improved delivery through biological membranes XIX: Novel redox carriers for brain-specific chemical delivery systems.

New dihydropyridine in equilibrium pyridinium salt-type redox carrier systems were developed in which the drug is linked via the ring nitrogen atom of nicotinamide. The rate of oxidation of the dihydropyridine forms, and thus the overall and brain-specific distribution of the corresponding 3-carbamoyl-1-carbamoylalkyl-drug quaternary salts, depends on the number of methylene groups separating the ring nitrogen and the carbamoyl function linked to the drug.