Originally Posted by johnt

Steve,

I suggest we do a trial trail before anyone goes out and buys a graphics tablet. (I have one already, a "Trust". Is this likely to come up to spec?) If that goes well, let's get other people involved.

soccertese,

You raise the issue of Azilect (rasagiline). It has no apparent effect on me. BUT ...

The literature reports that 1 mg of rasagiline is theraputically equivalent to 100 mg levodopa [1]. Now, 100 mg of levodopa (taken as part of Sinemet or Stalevo) would have a very noticeable effect on me.

How can those two positions be reconciled?

My hunch is that it's because the duration of rasagiline's effectiveness is so much longer. It is normal to take one rasagiline 1 mg pill per day, while Sinemet and Stalevo are often taken at 3 hourly intervals. So to get the same AOC (area under the curve) you need only one eighth (3 divided by 24) of the average impact. A dose of 12.5 mg of levodopa might not be noticed by many people, especially given all the other medications that we take. But that doesn't mean that the rasagiline is not "working".

(Interestingly, the difference is not in the main caused by rasagiline having a longer half life. An NIH archives document [2] states:

"Its mean steady-state half life is 3 hours but there is no correlation of pharmacokinetics with its pharmacological effect because of its irreversible inhibition of MAO-B."

I take that to mean that rasagiline comes in, does its job and departs, but that its effect carries on far longer:
"Studies in healthy subjects and in Parkinson's disease patients have shown that rasagiline inhibits platelet MAO-B irreversibly. The inhibition lasts at least 1 week after last dose." [2])

References

[1] "Levodopa Dose Equivalency", Claire Smith, 2010.
http://www.birmingham.ac.uk/Document...hLEDReview.pdf

[2] http://dailymed.nlm.nih.gov/dailymed...rchiveid=10668

John