A Simple HPLC Method for the Separation of Amphetamine Isomers in Urine and its Application in Differentiating between ‘Street’ Amphetamine and Prescribed D-Amphetamine

D-amphetamine has been increasingly prescribed to treat amphetamine abusers. Prescribing D-amphetamine requires laboratory evidence or confirmation of current use of 'street' amphetamine, using a method which should be capable of differentiating between 'street' amphetamine and prescribed D-amphetamine. We have developed a simple high-performance liquid chromatography (HPLC) method for the separation of the two isomers of amphetamine in urine and have assessed its use in differentiating between 'street' amphetamine and prescribed D-amphetamine. The method is reproducible, free from interference and has a detection limit of 0.1 microgram/mL for each isomer. Urine from patients prescribed D-amphetamine contained only a trace amount of L-amphetamine (less than 4%) whereas urine from those taking 'street' amphetamine contained more than 50% L-amphetamine. The method is applicable to confirmation of 'street' amphetamine misuse and for monitoring patient compliance with treatment. The presence of 4% or less L-amphetamine in urine would suggest that the patient is only taking prescribed D-amphetamine whereas the presence of L-amphetamine in higher concentrations suggests that the patient is taking 'street' amphetamine, with or without prescribed D-amphetamine.