Aim: Our aim was to characterize utilization patterns for drugs used to treat attention deficit/hyperactivity disorder (ADHD) on the level of the individual patient among Danish users, focusing on treatment duration, doses used, and concurrent use of ADHD and non-ADHD drugs.
Methods: Using the Danish Registry of Medicinal Product Statistics, we extracted data on 1,085,099 prescriptions for ADHD drugs issued to a total of 54,024 persons in the study period 1 January 1995 to 30 September 2011. For users in the final year of the study period, we further extracted 315,365 prescriptions for non-ADHD drugs. Drug utilization was characterized using descriptive statistics.
Results: The mean duration of ADHD treatment was highest (3.6-4.2 years) for patients initiating therapy at a young age (age<13). Dropout rate after receiving only one prescription was highest among off-label users (age<6 and age >17). All age categories showed an increase in the average daily dosage of methylphenidate used from 2003 to 2010. Concomitant treatment with methylphenidate and atomoxetine was rare, as only 2 % of methylphenidate treatment overlapped with atomoxetine treatment. Nineteen percent of methylphenidate instant-release treatment overlapped with methylphenidate controlled-release treatment. Users of ADHD drugs across all age categories had an increased use of drugs related to the nervous system, especially antipsychotics [standardized morbidity rate (SMR), 6.4-19.5] and antiepileptics (SMR, 4.0-5.5).
Conclusion: We found certain traits that warrant further investigation: the apparent increase in average daily doses, the low adherence to treatment among off-label users, and the increased use of other psychotropic medication.