Pharmacology: Pharmacokinetics: Memantine is well absorbed after oral doses. Peak plasma concentrations are achieved in about 3 to 8 hours. Plasma protein binding is about 45%. Memantine undergoes partial hepatic metabolism. The main metabolites are N-3, 5-dimethylgludantan and 1-nitroso-3, 5-dimethyl-adamantane. The majority of a dose is excreted unchanged via the kidney; some active renal tubular secretion and reabsorption occurs. The terminal half-life ranges from 60 to 100 hours, under the alkaline conditions the rate of elimination is reduced.