A comparative study found bioequivalent exposure for a lisdexamfetamine solution and reference capsules under its prespecified criteria. Bioequivalence concerns selected pharmacokinetic summaries; it does not mean that every participant had an identical concentration at every sampling time.
Rizea-Savu and colleagues studied single-dose comparative bioavailability in healthy volunteers. A validated liquid chromatography–tandem mass spectrometry method measured both lisdexamfetamine and dexamfetamine in human plasma. The former is the administered prodrug; the latter is its active conversion product. Measuring both avoids treating disappearance of the prodrug as disappearance of all active exposure.
Confidence intervals for the test-to-reference ratios of the specified primary pharmacokinetic parameters fell within the study’s predefined 80–125% acceptance range for both analytes. Prodrug profiles showed some formulation-related differences, whereas calculated dexamfetamine parameters were very similar. Peak concentration and area under the concentration-time curve summarize different properties: the highest observed exposure and exposure accumulated over time.
The acceptance interval applies to the statistical comparison of pharmacokinetic parameters. It is not permission for any individual tablet to contain an arbitrary amount of drug, and it is not an impairment threshold. The study did not compare cognition, treatment response or driving. Healthy-volunteer single-dose plasma data also cannot establish every outcome under chronic treatment or illness. Conversion of lisdexamfetamine helps explain why formulation dissolution and active-drug delivery need not have identical time courses. Forensic interpretation still requires the actual analyte, matrix, sampling time and exposure history, rather than converting a bioequivalence finding into an individual performance judgment.
See why plasma concentration and tested cognition remain separate measurements.