ADHD update: New data on the risks of medication

Medications — chiefly the stimulants dextroamphetamine and methylphenidate — are the only proven treatment for attention deficit hyperactivity disorder (ADHD), with its symptoms of distractibility, impulsiveness, and hyperactivity. But the benefits of stimulants last only as long as patients continue to take them, and worries about the risks of long-term use are again in the news.

Blood pressure and heart problems. Stimulants raise blood pressure and heart rate. New data are fueling a debate about how dangerous this is for people who take the drugs for extended periods. In spring 2006 an FDA panel reported on a study of physicians’ reports on ADHD medications recorded in its Adverse Events Reporting System database. More than 300 people taking the medications died suddenly. Only 25 of these deaths appeared to be drug-related, and autopsies indicated pre-existing heart abnormalities in some of these cases. There were also 26 incidents of symptoms such as chest pain, heart attacks, strokes, and arrhythmias. In a close vote, the panel members recommended a black box warning of cardiovascular risk on prescription labels.

 On the one hand, it’s estimated that fewer than 10% of adverse drug effects are actually reported. On the other hand, the rate of sudden cardiac death in the survey was much lower than in the general population. After further analysis, a second FDA panel canceled the black box warning but agreed to strengthen present warnings about prescribing these medications to anyone with high blood pressure or heart defects.

Meanwhile, the British equivalent of the FDA noted seizures and heart rate irregularities in a few people taking atomoxetine (Strattera), a new ADHD drug that is not a stimulant. The overwhelming majority of them had a prior history of seizures (which the drug did seem to exacerbate). The British agency required updating of the drug’s label.

The bottom line is that ADHD drugs are not likely to cause cardiovascular problems in anyone who does not already have underlying cardiac risk. But more such people are now using the drugs, because of the explosive growth in adult prescriptions. Careful screening and monitoring make sense.

Growth suppression. Many children start taking ADHD medications young and stay on the drugs for years, so the effect on growth is a persisting concern. Studies to date offer conflicting evidence.

In a large study with a broad focus, children ages 7–9 were followed for two years. At the end, those who had continuously taken ADHD medication during that time were on average half an inch shorter and 8 pounds lighter than those not taking the medication. To clarify the practical significance of this effect, researchers will have to do studies taking into account the adolescent growth spurt.

Abuse and diversion. Investigators examined the records of 64 hospital emergency departments and found 188 visits involving ADHD medications from August 2003 to December 2005. The overwhelming majority of the patients were children, and in 60% of cases the cause was intentional ingestion or an overdose, usually of a medication prescribed for someone else. About 15% of the patients had cardiovascular symptoms such as chest pain and high blood pressure; other symptoms included stomach pain, muscle weakness, and rashes.

The stimulants used to treat ADHD have some potential for abuse, because crushing pills and snorting (snuffing) them can produce a cocaine-like high.  The overwhelming majority of abusers were taking immediate-release preparations. These are increasingly being supplanted by extended-release formulas (and a skin patch), which are absorbed so gradually that they don’t cause a euphoric sensation and are therefore much less susceptible to misuse.

So, over all, new findings do not seriously challenge the consensus that most people who are properly diagnosed with ADHD will decide that the benefits of stimulant medications outweigh the risks.

December 2006 Update

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