Distribution of memantine in brain, liver, and blood of the rat

The distribution of 1,3-dimethyl-5-aminoadamantane (DMAA, D-145, memantine, Memantine), a compound used in the treatment of CNS disorders, is investigated in liver, brain, and blood of the rat. The tissue concentration of memantine is analyzed by gaschromatography after i.p. and p.o. administration. After i.p. application the blood levels are only about 1/10-1/20 of the concentrations found in liver and brain. The highest drug concentration in blood is obtained within the first 15 min, followed by liver and brain, 30 and 60 min after i.p. administration, respectively. The memantine concentration per g brain tissue is almost identical to the dose applied per g body weight. Lower brain levels are obtained if memantine is given p.o. However, in contrast to the rapid decrease after i.p. treatment, the plateau reached 1 h after p.o. administration does not level off within the next 3 h.