Deviant patterns of methylphenidate use in adults: A Danish nationwide registry-based drug utilization study

Purpose: Several survey studies have documented misuse of methylphenidate defined as the use of non-prescribed methylphenidate or use different from what was prescribed. We aimed to identify and characterize adults with deviant patterns of methylphenidate use in Denmark during 2007-2012. Further, we aimed to identify risk factors associated with deviant patterns of use. Methods: Based on individual-level prescription data, new users of methylphenidate were followed for one year after filling their first prescription on methylphenidate. Adult patients were identified with deviant patterns of use if they had ≥4 different prescribers and filled ≥1095 defined daily doses of methylphenidate during the year of follow-up. Risk factors were estimated by using logistic regression. Results: Among 20829 new users of methylphenidate, we identified 82 (0.39%) patients displaying deviant patterns of use. Characteristics associated with deviant patterns of use included an initial prescription for extended-release methylphenidate (OR2 4.35), age 25-49years at first prescription (OR2 2.49), general practitioners or hospital doctors as initial prescribers (OR2 3.06 and OR2 4.07) and prior use of drugs used in addictive disorders (OR2 2.08) or opioids (OR2 1.75). Sensitivity analyses revealed that the number of different prescribers alone does not seem to effectively identify deviant users of methylphenidate. Conclusion: We have identified characteristics associated with deviant patterns of methylphenidate use. Our results do not allow us to conclude if deviant users truly represent medical misusers.