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How Effective is Clonidine as a Medication for Treating ADHD?
One of the more frequent questions I receive concerning medication treatment for ADHD is about the use of clonidine. Clonidine is a medication that was originally developed to treat hypertension in adults. In child psychiatry, however, it is often used to treat tic disorders, aggression and conduct disorders, sleep disturbances, and ADHD. When used in the treatment of ADHD, it is sometimes prescribed alone but often used in combination with a stimulant such as Ritalin. The use of clonidine to treat ADHD and other behavioral difficulties in children has risen dramatically in recent years - from 20,000 prescriptions in 1990 to over 150,000 prescriptions in 1995.
Despite the frequent use of clonidine to treat ADHD, the use of this medication is not without controversy and questions about its safety and efficacy remain. I was thus pleased to come upon an article in the December issue of the Journal of the American Academy of Child and Adolescent Psychiatry (JAACP) that provided a comprehensive review of studies that have been conducted on the use of clonidine in the treatment of ADHD (Connor, D.F., Fletecher, K.E., & Swanson, J.M. (1999). A meta-analysis of clonidine for symptoms of ADHD. JAACP, 38, 1551-1560).
The basic method of a meta-analytic study is to first identify all studies that have been published on a topic. Next, the authors examine individual studies to identify those that seemed to use what they judge to be adequate scientific controls (i.e. studies that were designed and carried out such that the data is judged to be valid) and which present the results in a way that can be combined with other studies. Finally, the authors use a statistical technique that pools the results across the different studies and wind up with an overall estimate about the impact of the particular treatment being studied. The advantage of this approach - when it is done well - is that pooling the results of a number of individual studies can provide a better estimate about the utility of a particular treatment than can be obtained from a single study alone. This is because the results of the meta-analysis are based on a much larger sample, and are less influenced by any unusual factors that may have affected the results of an individual study.
So, in this paper, the authors began by identifying all published reports since 1980 on the use of clonidine to treat children and adolescents who exhibited symptoms of ADHD. Out of 39 such studies that were identified, 11 were judged to provide sufficient information to be included in the meta-analysis. These 11 studies reported data on a total of 150 patients under the age of 18 who were receiving clonidine for the treatment of ADHD symptoms - either alone, or in combination with other behavioral problems. Across these 11 studies, the average daily dose of clonidine was .18 mg/day and the average length of treatment was about 11 weeks. The vast majority of the participants in these studies were males.
The effect of clonidine on ADHD symptoms was computed separately based on reports provided by parents, teachers, and clinicians. Overall, beneficial effects of clonidine on ADHD symptoms were reported by all 3 sources, although parents reported greater benefits than either teachers or clinicians.
Based on the best estimate of the overall effectiveness of clonidine that the authors could calculate, the benefits provided by clonidine were in a range that would be generally considered to reflect a "moderate" size effect. To put this in perspective, the authors calculated that about 66% of children treated with clonidine would be expected to show a better response than a child treated with placebo. This is significantly below the effects that have been demonstrated for stimulant medications such as Ritalin and Adderall. Clonidine appeared to be more effective when used to treat children with ADHD symptoms alone, rather than ADHD symptoms in conjunction with other difficulties such as tics, conduct disorder, or some type of developmental delay.
The authors also examined the prevalence of side effects that were reported across the different studies. The most common side effect was sedation, as this was reported to be experienced by some patients in almost every study. The next most frequently reported side effect was irritability, which was reported to effect patients in 60% of the studies.
Summary And Implications
The results of this meta-analysis suggest that clonidine is a moderately effective medication to treat children with ADHD, particularly when co-morbid conditions are not also present. It is important to stress, however, that it appears to be less effective than stimulant medications and may be more likely to be associated with side effects, the most common of which would be sedation and irritability. Thus, the authors recommend that clonidine only be used as a second-tier treatment - that is, something to consider after treatment with stimulant medications has been carefully tried and judged to be unsuccessful.
This raises two important but related points - when to switch to clonidine and when to combine clonidine with a stimulant medication. I have received many questions from subscribers in which they have described how their child was started on Ritalin, and then switched to clonidine when that did not seem to work. Or, that clonidine was combined with a stimulant like Ritalin or Adderall when the stimulant alone was not felt to be sufficiently effective.
Although it is not possible to make statements about individual cases (remember, I am a Ph.D. and not an MD), I can say that in general, such approaches would not be recommended. Before switching to a completely different class of medication such as clonidine, one would generally want to do a thorough trial of the stimulant medications. This would include testing the initial stimulant at a range of different doses. If no dose was effective, or, the stimulant resulted in problematic side effects, one would then switch to a different stimulant and repeat the procedure. As discussed above in the context of the MTA study, if this careful procedure is followed, it will be very rare indeed for a switch to a different medication class to be required.
Thus, trying one stimulant and then switching because it is not helpful enough would usually be considered to reflect an inadequate trial of the stimulant medications. The same holds true for adding clonidine to an initially prescribed stimulant. The stimulants one might want to try before switching would include Ritalin, Adderall, and Dexedrine. Remember, even if one of two of these does not produce the desired effects, the other may still yield very good results.
In addition, if important difficulties remain for a child even when stimulants are producing the maximum possible effect, one should also consider the use of adjunctive behavioral interventions as an alternative to adding a new type of medication to the mix. There is really very little data on the efficacy of combining medications to treat ADHD, and I suspect that many children who receive multiple medications really do not derive any incremental benefits from the combination. There is, however, data that supports the combination of stimulant medication treatment and behavioral interventions. Thus, this should always be considered, in my opinion, as an alternative to combining medications.
Note: This article originally appeared in Attention Research Update, an online newsletter written by Dr. David Rabiner, a Duke University psychologist and former member of CHADD's Professional Advisory Board. You can learn more about Attention Research Update and sign up for a free subscription at www.helpforadd.com.