Objective: To investigate to what extent Western Australian (WA) patients with Attention Deficit Hyperactivity Disorder (ADHD) received prescribed stimulants in excess of their notified dose from WA pharmacies in 2004 (termed 'discrepancy').
Design and data sources: Analysis of administrative data about all people aged two years and older who were prescribed stimulants for the treatment of ADHD in WA, and had at least one stimulant prescription dispensed from a WA pharmacy during the period 1 January to 31 December 2004.
Outcome measures: Discrepancies were identified using minimum and maximum estimation methods (MinDE, MaxDE). We calculated for both methods the discrepancy prevalence by age and sex and annual surplus of stimulant accrued by age.
Results: Of the 15,190 ADHD patients who comprised the study population, 5.4% to 19.0% received stimulants surplus to requirement in 2004, with peak prevalences in 6-8 year-olds (MaxDE 20.1%) and 25-34 year-olds (MaxDE 27.6%; MinDE 10.5%). The amount of stimulant dispensed surplus to requirement was highly skewed, with median annual values that ranged from one to 4.1 standard bottles (100 tablets) of dexamphetamine 5 mg for the MinDE and MaxDE methods, respectively.
Conclusion: It is difficult to definitively estimate to what extent WA ADHD patients accrued excess stimulant medication using routine administrative data. Improvements to the WA Stimulant Regulatory Guidelines are recommended in the interests of patient safety, public transparency, methodological rigour and encouraging good prescribing practices.