Tailoring Medication Treatment in ADHD
I have always been amazed to find that a drug that works beautifully for one patient can be a total disaster for another. There is an explanation of why one patient will respond to coffee and another patient will have a bad reaction to coffee. Why Concerta will work great for one kid and horribly for another. The neurotransmitter receptors agonist and antagonist in our brains and bodies work differently in each of us and biological markers for this neurotransmitter activity are becoming more readily available. Physicians will soon have tools readily available to them that will take some of the guess work out of how you will respond to certain medical interventions.
I wrote in the last post about the fact that these lab test are, at the moment, prohibitively expensive and not readily available. It turns out that the ready availability and affordability of this testing is not as far off as I forecasted before. Genetic testing will also become more affordable and available which is important because genetics also plays a role in our response to treatment.
Interesting, I recently read that some people have a genetic variant that causes them to metabolize caffeine very rapidly and abruptly while most of us metabolize caffeine slowly and continuously. Methylphenidate (Ritalin) and Amphetamine (Adderall) work in a unique way and research is pointing us towards an understanding of why some people with ADHD respond better to Ritalin and others respond better to Adderall.
Atomoxetine (Strattera) and Guanfacine (Intuniv) work on completely different receptors and some people benefit from these drugs while others have no effect from them or adverse effects from them. A new class of drug called a Histamine 3 (H3) receptor antagonist is in development and has shown promise in the treatment of cognitive disorders. This class of drug may also be useful in the treatment of Fetal Alcohol Syndrome cognitive problems as well as in the treatment of Alzheimer's disease and schizophrenia. The H3 receptor antagonist work by enhancing the release of neurotransmitters such as histamine, ACh, dopamine and norepinephrine which are important to cognitive processing.
As researchers add medication to the ADHD arsenal, I believe that we will find that some patients will be uniquely helped by new medications like the H3 receptor antagonist and the Alpha-2 Adrenergic receptor agonist such as Intuniv while others will not be. I also believe that there will unique variations in the response to these medications and that these variations may not always be related to the subtypes of ADHD. It is possible that certain people with Inattentive ADHD (ADHD-PI) will be helped by Intuniv while others will have no effect from this medication.
We are not yet at the stage of medical testing where we can perform one lab test and know that you will or will not respond to a medication but more medications are available now and each of these medications target a different piece of the ADHD puzzle. With more puzzle pieces in place, we gain a better picture of what causes ADHD and of what unique treatment approaches will best suit each individual. The tailoring of ADHD treatment is not here yet but we are moving more quickly in that direction than I ever thought possible.
Drug News Perspective. 2010 Mar;23(2):99-103.
Therapeutic potential of histamine H3 receptor antagonists.
Selective antagonism of centrally localized histamine H(3) receptors has been shown to enhance the release of a wide spectrum of important neurotransmitters including acetylcholine, gamma-aminobutyric acid, dopamine and noradrenalin, among others, which play fundamental roles in cognitive processes, in an output-dependent manner. The cognitive-enhancing effects of H (3) receptor antagonists across multiple cognitive domains in a wide number of preclinical cognition models also endow confidence in this therapeutic strategy for the treatment of Alzheimer's disease, attention deficit hyperactivity disorder and the cognitive deficits often expressed in schizophrenia. Recent positive clinical reports are beginning to reinforce this optimism.
Labels: Inattentive ADHD Treatment