Methylphenidate and Cardiovascular Risk among Children

Study Design: 
* Self controlled case series analysis.
* Nationwide health insurance database, 1 January 2008 to 31 December 2011, in South Korea.

Participants:
* 1224 patients aged ≤17 who had experienced an incident cardiovascular event and had had at least one incident prescription for methylphenidate.

Results:
* Increased risk of arrhythmia was observed in all exposed time periods—that is, periods of treatment with methylphenidate: incidence rate ratio 1.61, 95% confidence interval 1.48 to 1.74.
* Risk was highest in the children who had congenital heart disease. 
* No significant risk of myocardial infarction was observed for all exposed time periods (1.33, 0.90 to 1.98)
* Note that risk was higher in the early risk periods between 8 and 56 days after the start of treatment with methylphenidate. 
* No significant increased risk was observed for hypertension, ischemic stroke, or heart failure.

Conclusions:
* This study found a significantly increased overall risk of arrhythmia associated with treatment with methylphenidate in children and young people with ADHD.
* While the risk of myocardial infarction was not significant overall, an increased risk is found after the first week of treatment, which remained significantly raised for the first two months of continuous treatment. 
* Though there was an increased risk for arrhythmia overall, the risk was substantially higher in patients with existing congenital heart disease.
* Though the absolute risk is likely to be low, the risk-benefit balance of methylphenidate should be carefully considered, particularly in children with mild ADHD.

Source: BMJ 2016;353:i2550