i was wondering if anyone knew what the halflife of dexedrine is within the body. i imagine that it's highly variable, but i'm merely looking for some sort of 'average'

the internet keep saying that it's 10-12 hours, but i have a hard time believing this. it doesn't make very much sense with my body. for me, after roughly graphing a few of my dosing attempts. (my doctor told me to find the right way), it seems that my personal metabolism of the drug is somewhere between 5 and 5.5 hours. of course, this is merely dependent upon my own personal reaction, and could be influenced by many other factors.

so i guess that i have another question. what determines that variant metabolism? does it have to do with the same "metabolism" that one thinks of in regards to weight change... the metabolism that burns caloric fuel...? or is it something else?

thanks.

... some sort of 'average'4 hours between doses (at least when I started).
Now 8 hours (->- to a day ->- to longer) - just forget to take it, though suspect that it's more my {mind,body} not being too fussed about taking it - I have no problems with the meds - but have switched into a much more self-directed flexible dosing regimen - which is turning out to involve 4 tablets or so of the meds daily (as a max) - previously 10-12 (when first I titrated up).

(drug) metabolism?wikiP Dexamphetamine (http://en.wikipedia.org/wiki/Dexamphetamine)
On average, about one half of a given dose is eliminated unchanged in the urine, while the other half is broken down into various metabolites (mostly benzoic acid).
However, the drug's half-life is highly variable because the rate of excretion is very sensitive to urinary pH.
Under alkaline conditions, direct excretion is negligible and 95%+ of the dose is metabolized.
The main metabolic pathway is d-amphetamine http://upload.wikimedia.org/math/2/b/4/2b48ec593552503e636269203bbf81e9.png phenylacetone http://upload.wikimedia.org/math/2/b/4/2b48ec593552503e636269203bbf81e9.png benzoic acid http://upload.wikimedia.org/math/2/b/4/2b48ec593552503e636269203bbf81e9.png hippuric acid. Another pathway, mediated by enzyme CYP2D6, is d-amphetamine http://upload.wikimedia.org/math/2/b/4/2b48ec593552503e636269203bbf81e9.png p-hydroxyamphetamine http://upload.wikimedia.org/math/2/b/4/2b48ec593552503e636269203bbf81e9.png p-hydroxynorephedrine.
Although p-hydroxyamphetamine is a minor metabolite (~5% of the dose), it may may have significant physiological effects as a norepinephrine analogue.
::noting::
CYP of CYP2D6 =>= CYTOCHROME P450
->-
(http://en.wikipedia.org/wiki/CYP2D6)wikiP CYP2D6 (http://en.wikipedia.org/wiki/CYP2D6)
Cytochrome P450 2D6 mixed-function oxidase system, is one of the most important enzymes involved in the metabolism of xenobiotics in the body
/ wikiP CYP2D6 (http://en.wikipedia.org/wiki/CYP2D6)
epinephrine =>= ADRENALINE
/ wikiP Dexamphetamine (http://en.wikipedia.org/wiki/Dexamphetamine)
what determines that variant metabolism? Pharmacogenetics has had one of its few successes on the cytochrome P450 family.
The answer would maybe be - genetic variation at this locus.
The wikiP site lists 'alleles' - alleles are genetic variants with (as a consequence of slightly different nucleotide compositions) -
differing degrees of functionality.
Think of alleles as kinda' chilled mutations :-)
Not a complete wipe-out of gene and hence function - more altered function.
... the metabolism that burns caloric fuel...? Also a 'cytochrome'
and yes - this fact is real interesting - because same type of structure -
but with wildly differing functions.
More on this later
(- an evolutionary perspective ->- sure!!!
:-)}.
You'll see from the connection between wikiP (above) on P450 and the cytochromes a,b,c of the ETC (below (http://en.wikipedia.org/wiki/Cytochrome))
wikiP Cytochrome (http://en.wikipedia.org/wiki/Cytochrome)
Cytochromes are either found as monomeric proteins (i.e. cytochrome c) or as subunits of bigger enzymatic complexes that catalyze redox reduction-oxidation reactions.
Cytochromes are generally membrane-bound proteins that contain heme groups and which carry out electron transport.
\ wikiP Cytochrome (http://en.wikipedia.org/wiki/Cytochrome)
- in that
oxidation, reduction
metabolism (albeit different definitions)
are shared by the two systems
though the commonalities are usually obscured by their wildly different biological functions ie
oxygen + food ->- energy
by the C(s) a-c of the ETC
xenobiotic neutralized ->-
by the C(s) P450 of the liver