Sunday, April 14, 2013

the difference between methylphenidate and amphetamine

i know someone who uses ADHD medicine, so i was curious as to what the difference between the two types of medicine ingredients used are:
* methylphenidate
* amphetamnine
after reading alot today i think i've broken down the difference between the two:

methylphenidate (medicines like concerta and ritalin):
* blocks reuptake of dopamine (DRI)

* increases the body's production of dopamine, but to a less extent than amphetamine

* slows reuptake of dopamine

"acts as a substrate for DAT and slows reuptake by a secondary acting mechanism through the phosphorylation of dopamine transporters."

* increases the body's production of dopamine (RA)

they seem really similar--their 2 main effects are inversely stronger than the other.

UPDATE 20131001

Here's some feedback about the subject from a pharmacist friend of mine in the US:

You're spot on with regards to the chemical action/brain chemistry. Dopamine is the main target, whether that be by blocking reabsorption or increasing production, but there is some norepinephrine activity with both as well. Two main characteristics that I think contribute to clinical efficacy with both is how your body metabolizes the drug and the drugs respective half life. The amphetamine salts have an active metabolite, meaning the drug has to be chemically changed through metabolism to an active form, in this case dextroamphetamine before it exerts an effect. Adderall is formulated in about a 25/75 ratio of amphet/dextroamphet. This process happens in the liver, and why the phosphorylation that you mentioned in your blog is important . Much more importantly in my opinion though is that methylphenidate has a much shorter half-life, 2-3 hours for the immediate release formulation (Ritalin) and 4-5 hours for the extended release formulation (Concerta, Focalin). Amphetamine salts have a half life of up 14 hours, depending on liver function. Longer half life means longer dosing intervals, which leads to better patient compliance which leads to better clinical outcomes. Ritalin IR has to be dosed two to three times daily and leads to a peak/trough drug level effect which is not ideal. This effect led to development of an ER formulation of methylphenidate. Concerta is ER, so can be dosed once daily, but with a short half life still poses more of a peak/trough effect compared to Adderall and dosage increase is often warranted to get trough levels to stay above the therapeutic level. Adderall is also dosed once daily, but with a longer half-life, typically dosing is more stable and drug levels avoid that peak/trough effect. Of course, both drugs a highly addictive and are habit-forming, which I think leads to a big part of the social stigma here in the states. (despite the same addiction potential of alcohol, tobacco, marijuana, etc stimulant drugs are almost seen as taboo to some)
Hope that gives a little more insight or something to further research. Medicine is as much of an art as it is a science, if something works well for some, it doesn't necessarily extrapolate to you. Find what works well for you, fine tune the dosing and you'll be well on your way.

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