Ritalin, a popular medication used to treat attention deficit hyperactivity disorder (ADHD), may up the risk of abnormal heart rhythm shortly after being taken, a new study has found.

Ritalin is one of the brand names under which methylphenidate – which the researchers linked to a 61 percent higher risk of arrhythmias during the first two months of use – is being sold on the market. This drug is a stimulant of the central nervous system and is used for treating ADHD as well as narcolepsy.

An international team of scientists analyzed over 114,000 South Korean patients under age 17, finding more than 1,200 cardiac events in the group newly given methylphenidate in the period 2008 to 2011.

The cardiac events recorded where arrhythmias, hypertension, myocardial infarction or heart attack, stroke, and heart failure, with the first condition most likely to occur within two months of use and with the highest risk in the first three days. The arrhythmia risk was most pronounced in kids with congenital heart disease already.  

"With the increased use of drugs for ADHD globally, the benefits of methylphenidate should be carefully weighed against the potential cardiovascular risks of these drugs in children and adolescents,” the authors wrote May 31 in the journal BMJ.

The absolute risk, however, is likely low – most kids on the drug should not experience heart issues, according to John Jackson of Harvard School of Public Health in an accompanying editorial.

In the average child, the risk of serious cardiovascular events is extremely small, while an “absolute excess risk” tied to the drug is also probably small, he explained.

There are concerns around stimulants like methylphenidate potentially affecting heart health, according to the authors. Other experts also advise cardiac patients to avoid caffeine and such other items following this principle.

They pointed out, however, that theirs is an observational study that presents no final conclusion and causality.

Jackson also cited the treatment and labeling guidelines for these stimulants, which suggest caution in use among kids with a heart disease history.

Recently, researchers from the U.S. Centers for Disease Control and Prevention (CDC) called for parents of young ADHD patients – those ages 2 to 5 – to try behavior therapy first before using medication.

The new recommendation followed findings that 75 percent of kids with ADHD are provided with drugs while only about half receive psychological services.

Photo: Pedro Ribeiro Simoes | Flickr