AVAILABILITY OF LIPOSOMES AS DRUG CARRIERS TO THE BRAIN

Phospholipid vesicles, also known as liposomes, were examined for thei r ability to act as a drug carrier to the brain. 9-Amino-1,2,3,4-tetra hydroacridine (THA), a centrally acting acetylcholinesterase inhibitor , was used as a model drug. THA was encapsulated in dehydration-rehydr ation Vesicles (DRV) composed of egg yolk phosphatidylcholine, cholest erol and dipalmitoylphosphatidic acid (molar ratio, 10/10/1) and injec ted into the heart of mice. The toxicity and side effects of THA were reduced by encapsulation in liposomes. The THA concentration in the mo use brain after injection of THA-encapsulated DRV at a dose of 2 mg/kg remained higher than that of free THA at the same dose. Effective con centration of TMA in the brain was also prolonged by the use of liposo mes, although accumulation of THA in the spleen and kidney was observe d. We, therefore, concluded that liposomes are useful as carriers of d rugs to the brain.