TORONTO – As of yesterday, Health Canada has issued warnings about the two main drug classes that are used to treat attention deficit hyperactivity disorder, or ADHD — methylphenidate and amphetamine-based drugs.
Although Health Canada doesn’t provide any numbers, the agency says it completed safety reviews, and noted reports of suicidality associated with these drugs.
Suicidality refers to suicidal thoughts, suicidal actions (such as suicide attempts), and very rarely, actual suicides.
Health Canada is very careful to acknowledge that there’s no scientific evidence that these drugs are actually causing this behaviour. Also, the agency recognizes that ADHD is associated with other mental health conditions which may in themselves increase the risk of suicidality. However, the basic message is that they have some reports, and they want patients and practitioners to be aware. Clearly, they are erring on the side of caution.
People may be wondering where these reports of suicidality are actually coming from.
This requires some background on our drug safety procedures. Drugs are initially approved based on data from clinical trials showing benefits outweighing harms. However, for about 20 per cent of drugs, there are harms that are so rare that they only truly become evident after the drug is marketed and used by a large number of people.
Vioxx is a good example of this – it was used for four years before it came off the market due to cardiovascular side effects. Health Canada has a voluntary post-marketing adverse event reporting system for physicians and patients, and it is very likely that they’ve received a small number of reports of suicidality through this system.
This is not enough to be scientifically valid, but as Health Canada waits for the scientific data to emerge, they want doctors and families to at least be vigilant of suicidal risk and suicidal behaviour in these kids.
TOP 5: Attention Deficit Hyperactivity Disorder
1. Key features: ADHD is a chronic condition which is diagnosed in childhood and characterized by 3 main features: hyperactivity, impulsivity, and/or inattention.
2. Coexisting conditions: As many as one-third of children with ADHD have one or more coexisting conditions such as learning disabilities, mood disorders, and/or sleep disorders.
3. Association with Suicidality: In a study by SP Hinshaw and colleagues in the Journal of Consulting and Clinical Psychology in 2012, children with ADHD were shown to have higher rates of suicidality than other children. This alone may account for the reports received by Heath Canada, independent of medication use.
4. Treatment: Treatment is usually a combination of behavioural therapy – which involves trying to change behaviour by changing the child’s environment and interactions, and medical therapy, which mostly involves stimulants such as those discussed above.
5. Effects of stimulant drugs: The exact mechanism of action of stimulants in ADHD is unknown, but we have several randomized controlled trials and meta-analyses which show that they are more effective than placebo in reducing the core symptoms of ADHD. This was reviewed by RT Brown and colleagues in Pediatrics, in 2005.
The key message here is that this drug clearly has important beneficial effects, and both doctors and patients will now have to carefully weigh these beneficial effects against known side-effects and this new theoretical concern about suicidality.
For now, I would say that this will not change practice for the vast majority of kids with this disorder, but vigilance on the part of practitioners, families, and patients is required.
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