Association between Methylphenidate and Risk of Trauma Related Accident and Emergency Admissions: a self-controlled case-series study

KK Man1, EW Chan1, D Coghill2, I Douglas3, P Ip4, LP Leung5, MS Tsui5, WHS Wong4, IC Wong1,6. 1Centre for Safe Medication Practice and Research, Department of Pharmacology and Pharmacy, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, Hong Kong, 2Division of Medical Science, School of Medicine, University of Dundee, Dundee, UK, 3Department of Non-communicable Disease Epidemiology, London School of Hygiene and Tropical Medicine, London, UK, 4Department of Paediatrics and Adolescent Medicine, Li Ka Shing Faculty of Medicine, Hong Kong, Hong Kong, 5Department of Accident and Emergency, Queen Mary Hospital, Hong Kong, Hong Kong, 6Centre for Paediatric Pharmacy Research, University College London School of Pharmacy, London, UK.

Children and adolescents with Attention-Deficit/Hyperactivity Disorder (ADHD) are prone to sustaining trauma that requires Accident and Emergency (A&E) admission (1). Methylphenidate (MPH) can reduce ADHD symptoms and thus theoretically may reduce the risk of trauma related A&E admission but previous studies did not provide clear association. This study examined the association between MPH and trauma related A&E admission. 17,381 patients aged 6-19 years who received at least one MPH prescription were identified using Hong Kong Population-based electronic medical records on the Clinical Data Analysis & Reporting System (2001-2013). Using self-control case series study design (2), relative incidence of trauma related A&E admissions comparing periods when patients were exposed to methylphenidate with non-exposed periods. Among 17,381 patients prescribed MPH, 4,934 had at least one trauma related A&E admission. The rate of trauma related A&E admission was lower during exposed compared to non-exposed periods (Incidence-rate-ratio [IRR]=0.91, 95% confidence interval [CI]=0.86-0.97). The findings were similar when only incident trauma episode was assessed (IRR=0.89, 95%CI =0.82-0.96). Similar protective association was found in both male and female patients. In validation analysis using non-trauma related A&E admissions as a negative control outcome, no statistically significant association was found (IRR=0.99, 95%CI=0.95-1.02). Sensitivity analysis testing for uncertainty over the precise period of MPH exposure demonstrated consistent results.

Table 1: Self-controlled case series analyses for association between MPH and trauma related A&E admission

In conclusion, this study supports the hypothesis that MPH is associated with a reduced risk of trauma related A&E admission in children and adolescents. The use of MPH treatment is shown to prevent injuries in this group of high-risk patients and this potential benefit should be considered in clinical practice.

(1) Ertan C et al. (2012). Emerg Med J. 29(11):911-4

(2) Whitaker HJ et al. (2006). Stat Med, 25(10), 1768-1797.