Do ADHD Stimulant Drugs Stunt Growth?

Here are seven questions or factors we need to address to assess the validity of studies on ADHD stimulant medications and their effects on growth:

1. Is there a history of prior stimulant medication use? Surprisingly, a number of studies on the inhibitory effects of ADHD stimulant medications either neglect or downplay the fact that children in their studies had a previous history of stimulant medication usage for their conditions. This can seriously confound effects, for if a child was taking a stimulant medication previously, he or she may still be on track for a lower baseline growth rate. Furthermore, if a child was taken off stimulant medications recently, there remains the possibility that his or her system is beginning to play "catch-up" by displaying a greater-than-normal increase in growth following a medication "holiday". In either case, baseline readings are skewed, and these effects muddy the accuracy of current stimulant medication studies on growth effects. Poulton and Nanan make this observation in their article on prior treatments with stimulant medication and growth in children with ADHD. They go on to say that growth is an accurate indicator of prior treatment with stimulant medication.
   
   
2. Beware of the pretreatment bias with regards to effectiveness of stimulant medications: Poulton and Nanan also warned about the natural bias of individuals with a previous treatment history of stimulants in that they have already proven to have a greater tolerance to potential side effects (otherwise they would have likely discontinued earlier stimulant treatments) and an overall higher levels of compliance and positive response to stimulant medications. This too, can give a potential "false positive" with regards to evaluating the effectiveness of current stimulant medication treatments for ADHD.
   
   
3. Do untreated children and adolescents with ADHD have different growth patterns than non-affected children? This is also a much-neglected consideration. Spencer and coworkers performed a study in which they saw a slower growth rate in the earlier years for children with ADHD, which was followed by a significantly later "catch" up period. In other words, compared to non-ADHD children, individuals with ADHD may be more predisposed to being "late bloomers", even when they are unmedicated. This potential difference in growth patterns between ADHD'ers and non-ADHD'ers, while still highly debatable, should at least raise the question as to whether delays in growth patterns for medicated individuals with ADHD can actually be attributed to the medications or to the nature of the disorder itself (or a combination of both).
   
   
4. Do "drug holidays" work? This is actually comprised of several questions and considerations. It is not uncommon for parents or prescribing physicians to allow for "drug holidays" for unmedicated ADHD children. These holidays can vary from a few days to longer periods such as an entire summer vacation. If the period of these drug holidays is long enough, such as in a summer-long study by Gittleman-Klein and coworkers on methylphenidate and growth, significant changes may be seen. This study saw a relative increase in weight but not in height following a summer off of medication of the stimulant methylphenidate (Ritalin). Of potential interest was the observation that following a second holiday from medication the following summer, a relative increase in height but not in weight was observed. It is entirely possible that the duration and frequency of drug holidays may effect the two parameters (height and weight) in slightly different fashions. Another article by Poulton suggests the possibility that height gains may take longer to remedy because gains in weight may drive subsequent growth in height.
   
   
5. Does the type of stimulant medication make a difference? In a preliminary sense, it appears that the answer would be "yes". For example, it appears that the stimulant drug dexamphetamine (d-amphetamine, also called by common name Dexedrine) has a greater inhibitory effect on growth during the first year of treatment than does methylphenidate (Ritalin, Concerta, Daytrana).
   
   
6. What is the typical extent of growth impairments due to stimulant medications? We need to be careful on this one, especially with regards to some of the earlier factors and considerations mentioned above. Nevertheless, a review of the literature seems to indicate a relative deficit in growth of around 1 cm per year for up to about 3 years which can be attributed to stimulant medication treatment. Furthermore, it appears that weight may be even more affected than height due to stimulant medication treatment, although it also appears that weight differences are easier to remediate than height differences and therefore pose less of a concern.
   
   
7. Are the growth changes due to stimulant medication temporary or permanent? Although hotly debatable, it appears that growth impairments due to prescribed stimulant medication usage is more of a short-term effect. A follow-up study of medicated ADHD children into adulthood indicated that even at moderately-high doses of the stimulant medication methylphenidate (45 mg/day average), medicated children with ADHD eventually reached normal final heights when compared to controls. It is worth mentioning, however, that these children eventually discontinued their medications. It is unclear as to what the effects may have been had they continued on with the methylphenidate usage into adulthood (especially since there has been a sharp trend towards continuing stimulant medication treatment into adulthood for adult ADHD).

ADHD Medication Recall: Dextroamphetamine Sulfate

ADHD Medications

ETHEX Corp. voluntarily recalls batches of Dextroamphetamine Sulfate

While far from catastrophic, it is worth mentioning that there was a recent recall by some manufacturers of the ADHD stimulant medication Dextroamphetamine Sulfate. Dextroamphetamine, which also goes by the trade name Dexedrine or Dextrostat (by other manufacturers), is a relatively potent stimulant used to treat ADHD and anxiety disorders. ETHEX issued a release to the FDA on Tuesday October 15, 2008 about a recall of the 5 mg tablets of its version of the drug. Tests had shown that a sample of the medication contained oversized tablets that included a noticeably higher dosage than labeled (up to twice as high in some cases).

The good news surrounding this release is that no wholesalers or retailers of the drug have filed reports citing oversized tablets of the 5 mg of the drug (click here for a pictured link to this product). Additionally, the company manufactures 10 mg tablets of the same product, so even an accidental "double dose" (10 mg) of the medication does not exceed the dosing maximum for this particular product line. The frequency of negative side effects is often limited when total dosing is below 15 mg, and the drug typically does not result in severe reactions until around 30 mg (three times the "double dose") is taken.

Hypothetically speaking, an accidental overdose of Dextroamphetamine sulfate could cause an array of symptoms and side effects including an increased heart rate (tachycardia) and elevated blood pressure (hypertension). The risk is increased if antidepressants of the Monoamine Oxidase Inhibitor family (such as Selegiline, Zelapar capsules or transdermal Emsam patches) have been used within two weeks of the dextroamphetamine sulfate medications.

Aside from possible risks for those with current cardiovascular disorders, it is unlikely that any major side effects would occur from taking the occasional oversized capsule. Nevertheless, it raises the concern about medication dosing and how important knowledge regarding the dose-dependant effects of ADHD medications truly are. In a future post, we will explore how different doses of the same medication can often result in vastly different responses in a patient.

ADHD medications