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High Dose Stimulant Treatment for Adult ADHD

September 13, 2013

All ADHD medications that are FDA approved to treat adults have designated maximum daily doses. It is important to understand how these daily maximum doses are determined in order to consider higher doses beyond these thresholds.  The FDA receives the clinical registration trial research and it makes a determination of maximum daily dose based on the presented data. If, for example, a clinical trial had a maximum dose of 50 mg a day then the FDA will only approve the drug with a maximum daily dose of 50 mg.  An example of this is Vyvanse where the trial looked at 30 mg, 50 mg and 70 mg a day. Maximum daily dose approved is 70 mg.

In some cases where the clinical trial evaluated several doses, the FDA may only approve a maximum dose in the middle dose range from the trial because the higher dose didn’t demonstrate a statistically significant difference in effect. Case in point, Concerta maximum daily dose in the package information is 72 mg, although the U.S. adult trial went to 108 mg a day. However the trial protocols are not designed to answer the question “If you don’t respond to 72 mg a day, will you respond to 108 mg a day”.

Where am I going with this? I have several patients at what would be considered as very high doses of stimulant medication-methylphenidate 400 mg a day, Vyvanse 200 mg a day. Unsafe? Well neither patient complains of problematic side effects for which they would stop the medication. Also, blood pressure and pulse are in normal range. We got to these doses because lower doses didn’t have any effect until we went higher. In each of these cases, I have ordered stimulant blood levels to see if blood levels were too high. In fact, in each case the levels were lower that what was expected by mathematical extrapolation.

The point? There are a group of ADHD adults who are very fast metabolizers who will only respond to very high stimulant doses. Since most of the metabolism of amphetamines and methylphenidate occurs outside the liver, I’m not sure obtaining a liver P450 enzyme profile to determine metabolism will be useful.

If you have ADHD and have not responded to appropriate stimulant doses, then consider seeing an ADHD adult psychiatrist who has experience and comfort with this dosing concept.  That’s what true expert clinicians are for.

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