The effect of ephedrine isomers and their oxazolidines on locomotor activity in rats

1. The four stereoisomeric ephedrines and four oxazolidines formed by reaction of each ephedrine isomer with salicylaldehyde were tested for their ability to increase locomotor activity in rats. 2. All ephedrine isomers except (-)pseudoephedrine increased locomotor activity; the order of potency was (-)ephedrine > (+) pseudoephedrine > (+) ephedrine. 3. All oxazolidine derivatives increased locomotor activity except (-)pseudoephedrine oxazolidine. 4. The oxazolidines derived from (-) and (+) ephedrine were slightly more active than their parent drugs. (+) Pseudoephedrine oxazolidine was less active than its parent. 5. Half-lives of hydrolysis were measured for the oxazolidines in aqueous buffer, ephedrine oxazolidines hydrolyze faster than pseudoephedrine oxazolidines.