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What does being careful mean? Check on wikipedia or whatever to see
if it's known what enzymes are responsible for the degradation of the
drug in question. Most of the time, it will be a cytochrome P450
enzyme in the liver (CYPXYZ, where X and Z are numbers and Y is a
letter); 20-25% of the time, it will be CYP2D6. If an enzyme other
than MAOB (or maybe MAOA) is listed, it should be fine. If the enzyme
responsible for its degradation isn't known, or is known to be one of
the MAO enzymes (MAOA or MAOB), then you should be careful. MAOA is
probably fine unless you're taking very large doses of selegiline
(around 40 mg/day or more), but you should be cautious and start with
a low dose. If it's metabolized by MAOB, then you should know that
the drug will last 10 to 100 times as long while you're on selegiline,
and that it will continue to last much longer for several weeks. (A
bioassay my friend did seemed to show that even after 4 weeks of
abstaining from selegiline, a certain substance lasted about twice as
long as it normally does.)
Things to be very very careful about, and which are likely to be
metabolized by MAOB, include all phenylethylamines. That means
molecules which have this structure at their core:
http://en.wikipedia.org/wiki/Phenethylamine
That includes pretty much everything listed in PIHKAL (http://en.wikipedia.org/wiki/Pihkal
).
It's important that the nitrogen atom (the 'amine' in
phenylethylamine) not have anything attached to it b, since MAOA and
MAOB replace that nitrogen atom with a couple of oxygen atoms.
While amphetamine and methamphetamine have this phenylethylamine core
structure, they also happen to be metabolized in the liver (by CYP2D6,
at least for amphetamine), which means that their metabolism is
probably not significantly affected by selegiline. However, because
amphetamine stimulates the release of dopamine and norepinephrine into
synapses, and because selegiline slows the degradation of dopamine in
the cytoplasm, there may be an interaction between the two drugs other
than through metabolism. Then again, selegiline itself metabolizes
into amphetamine and methamphetamine, and it's believed that this is
partially responsible for the drug's effects. (It's also responsible
for the false positive on drug tests. Well, calling it a "false"
positive is debatable, since there actually is amphetamine and
methamphetamine in your blood, even though there was none in the pill.)
Incidentally, since I mentioned phenylethylamine (PEA), combining
selegiline with PEA has some pretty powerful effects. Profoundly
energizing, thoroughly pleasant, and likely with potential for
addiction. Low doses of PEA (10-60 mg/day) combined with selegiline
(>= 5 mg/day) have been used with some success to treat depression
with no adaptation or tolerance observed, but PEA doses above 100 mg
tend to be more like snorting ritalin. Or so I hear. Not that you
asked.
As for what you did ask about: Modafinil is metabolized by CYP3A4, so
it shouldn't be affected by selegiline. (Also, I've combined the two
and not noticed anything unusual.) Donepezil is metabolized by CYP3A4
and CYP2D6, and its structure is totally unphenylethylamine-like, and
besides, most of it is excreted in the urine unchanged. (That's what
tends to happen when a compound has got a 70 hour half-life.) Also
very unlikely to interact with selegiline.
Jonathan
> I am also thinking that your unemployed status must be related to your
> selectivity and the economic environment, because it seems that the
> USA could use somebody with your education, understanding, and
> intelligence on its payroll.
Yeah, well... I'm picky. I finally landed a phone interview with
23andMe, which will take place tomorrow. We'll see how that turns out.
> I have some old intro anatomy and physiology texts, and they have some
> information on physiology, but to be honest, I never was able to
> understand the physiology components well.
>
> Do you happen to know of any good texts that are well-illustrated
> visually (as to combine as many of my learning senses as possible for
> needed reinforcement) oriented physiology (or anatomy and physiology)
> texts that may assist me in understanding the medical field better?
Physiology texts aren't going to have much to say about
neurophiology. For that, you'll have to look in neuroscience texts.
Or Wikipedia.
There's a lot to be learned about pharmacology, too. For example, the
Wikipedia article on pharmacokinetics (http://en.wikipedia.org/wiki/Pharmacokinetics
) is relevant to this discussion.
I actually haven't taken any classes or read any textbooks in human
physiology. The closest I've come was a class in biochemistry, a
general biology course, and the introduction to neurobiology class
that UCB offers.
Also, having taken 10 semester-units of organic chemistry helps...
J
Good luck with that! 23andMe is one of those things I want to try when
the price has come down to the $100 range and I have the spare cash;
they seem like a company doing interesting things.
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gwern
http://www.geek.com/articles/news/23andme-drops-dna-tests-drop-from-499-to-99-for-dna-day-20100423/
I don't think the price will get down to $100 in the next two years
(and I don't think they'll do the $99 DNA day special again next year—
I think it was too successful this last time), but in maybe 10 years
full DNA sequencing should cost about as much as SNP chip analysis
does now.
The phone interview went well, I think. We'll see if they call me in
for an in-person interview.
... It's amazing how off-topic this thread has gotten. ...
Jonathan