Here is some food for thought...
VOLKOW et. al.  1995.   IS METHYLPHENIDATE LIKE COCAINE?   Studies on 
Their Pharmacokinetics and Distribution in the  Human Brain.  Archives 
of General Psychiatry. 52:456-463 
This paper provides a nice comparison of methylphenidate and  cocaine.  
The first sentence states, "Cocaine which is one  of the most 
reinforcing and addictive of the abused drugs,  has pharmacological 
actions that are very similar to those  of methylphenidate 
hydrochloride..."  It's noted that  "cocaine and methylphenidate 
substitute for each other on  discriminative experiments..."
The authors indicate that cocaine and methylphenidate have  similar 
affinities for the dopamine transporter.  This is  interesting because 
cocaine's addictiveness is related to  it's ability to inhibit the 
dopamine transporter.  But  methylphenidate doesn't have the same 
addiction profile as  cocaine.  While humans will repeatedly self-
administer  cocaine, they do so much less frequently with 
methylphenidate.  
The authors inject radiolabeled cocaine or methylphenidate  into humans 
and baboons and take PET scans of their brains.   They ask the humans to 
rate on a scale of 0-10 how high  they are (0 is sober, 10 is stoned-out-
of-your-mind).  Then  they see if there is a correlation between the 
subjective  stonyness rating and the drug activity noted on the scans. 
From the scans it's found that methylphenidate and cocaine  take a 
similar amount of time to reach peak concentration in  the brain, but 
the cocaine stays at peak levels for less  than 5 minutes, while 
methylphenidate stays at peak levels  for up to 20 minutes..
Now combining this data with the subjective stonyness  ratings reveals 
that the high is correlated to the *change*  in drug concentration.  So 
the faster the dopamine levels  change in the synapse, the better the 
high.  
To simplify this, when you take cocaine you shoot your  dopamine levels 
up from 0-10.  40 minutes later you are back  down to around 4.  You can 
take more cocaine and knock your  dopamine back up to 10 (a change of 
6).
With methylphenidate you shoot up from 0 to 10, but then  after 40 
minutes, your dopamine is still at 8 or 9.  If you  take more you can 
restore levels to 10, but this is only a  change of 1 or 2.  Remember, 
it's the rate of increase, the  change in dopamine levels that causes 
the high.
Ritalin and Cocaine are very similar.  They also have some differences 
that turn out to  be significant when it comes to addiction and abuse.
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IOW, your comments re the comparison between Cocaine and MPH were, at 
best, simplistic. Cocaine's biophysical action of addiction is 
significantly different than that of MPH. And MPH does not emulate that.
I hope I have cleared up your misconception.
               The Few. The Proud. The Chosen.
                     markprobe@aol.com
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 * CMPQwk #1.4 * UNREGISTERED EVALUATION COPY
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