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Ernie, You wrote about getting information on Sinemet pharmacokinetics. I am very interested in such information. I would appreciate copy or source to e-mail or write to to obtain it. Most of what I know is included in the several sub-pages on my homepage. If you are interested, the URL is the bottom line of my signature. Comments about questionable information or whatever are welcomed. <<<Seeking clarification on the "half-life", I was told that the "exponential decay rate" referred to the drug once it was in the blood plasma. From this, I conclude that standard Sinemet will quickly reach its peak level and then follow the exponential half-life decay described. Sinemet CR will, however, deliver its designed dosage evenly per hour until exhausted. At this point, the half-life decay rate will again come into play for the drug remaining in the blood.>>>>> The metabolic reactions are "decaying" the levodopa. The ones that occur in the blood do their thing not knowing where or how or when the levodopa got into the blood. Equilibrium, two-way, reactions depend upon concentrations of reactants and products. (I believe that Brian Collins is a bit 'locked' onto flow rate controlling only whereas transport rates often depend upon concentration - in addition to the reaction rate dependence.) The regular may get quickly dissolved (or be pre-dissolved) but be metabolized in the stomach if too much food or too-long digesting happens. Also, if no food digesting, the transport into blood may be minimal also. The CR lump may not completely dissolve - it may leave in the feces as a residual. It's surface area decrease is part of the flow-rate determination. There may also be acidity, bile components, and other factors in dissolving of the levodopa and carbidopa from the tablet. -- ron 1936, dz PD 1984 Ridgecrest, California Ronald F. Vetter <[log in to unmask]> http://www.ridgecrest.ca.us/~rfvetter