Kinetics, salivary excretion of amphetamine isomers, and effect of urinary pH

Amphetamine was administered to healthy subjects as the racemic mixture and as (+)- and (-)-isomers under conditions of urine acidification and alkalinization. Plasma and saliva concentration of each isomer was measured and the kinetics of the individual isomers were determined. (+)-amphetamine was eliminated more rapidly than the (-)-isomer. The difference in half-life between isomers was maximal under basic urinary pH conditions. Saliva amphetamine levels were higher than plasma levels and in the postabsorptive phase were predictably proportional to plasma drug levels.