Alternative routine for reporting chiral amphetamine test results in assessment of attention-deficit/hyperactivity disorder medication: experiences from 2013 to 2023

This study evaluated an alternative routine for reporting urinary chiral amphetamine results in assessment of attention-deficit/hyperactivity disorder (ADHD) treatment with amphetamine medications and for detecting side-use of illicit racemic amphetamine. Currently in Sweden, only enantiopure d-amphetamine-based ADHD medications (lisdexamphetamine dimesylate and dexamphetamine sulfate) are approved. It is therefore unsuitable to express the chiral result as the l/d-ratio, as before, because l-amphetamine should not be present provided treatment compliance. A new routine for LC-MS/MS chiral amphetamine testing was therefore introduced in 2020, whereby the relative proportion (%) of l-amphetamine and the total amphetamine and creatinine concentrations are reported. Evaluation of the new routine on 24,354 results from 2013 to 2023 revealed that it was useful to distinguish ADHD medication adherence from illicit drug use as the source for a positive test. The l-amphetamine proportion also reflected the enantiomeric content of the medications used. Overall, most results confirmed adherence to ADHD medication, as the l-amphetamine percentage was <1% in 76% of samples (2023) which is the recommended cutoff with enantiopure d-amphetamine medications. However, in all years, illicit drug use was indicated (>40% l-amphetamine) in 8.3%-14.5% of cases. In conclusion, this study demonstrated the clinical value and utility of a new routine for reporting urinary chiral amphetamine results to differentiate adherence to ADHD medication from illicit drug use. Unlike the l/d-amphetamine ratio, it considers differences in total amphetamine concentration and urine dilution, factors that can affect the interpretation.