The paper pointed to by soccertese is very interesting [1].
There is nothing magic about Rytary: it contains levodopa and carbidopa in a 4:1 ratio, just like Sinemet. The difference is that a capsule of Rytary contains in effect three sub-doses: an immediate release sub-dose, and two controlled release sub-doses timed to provide benefit later.
You can get a similar effect by using four standard immediate release doses of C/L. A detailed description of this approach is given in the thread:
Approximating the pharmacokinetics of Rytary using IR C-L
Approximating the pharmacokinetics of Rytary using IR C-L
Rytary competes with some of the longer half-life dopamine agonists such as ropinirole. See:
Levodopa Dose Equivalency
Levodopa Dose Equivalency
The ebb and flow of levodopa equivalent plasma levels as we go from dose to dose can be visualized by using the following app:
Parkinson's Disease Measurement: PwP, surveys, trials, analysis
The general strategy is to dose up to beyond the "on" threshold. But, not to take plasma concentrations above a level which causes levodopa induced dyskinesia. With C/L, TMAX, the time taken for a dose to reach maximum concentration is about 60 minutes. Once at its maximum, concentrations halve about every 90 minutes, this is called THALF. The aim is to time the taking of the next dose so that it kicks in before concentrations fall to a level causing an "off". The smoothing effect of closer, but smaller doses allows a PwP to take a higher total daily dose, without going into dyskinetic levels.
Control becomes harder as the disease progresses because less dopamine is being produced by the body, and there are lower dopamine reserves to fall back on. But, nevertheless, in my opinion most PwP would benefit from an analysis of their drug regimens.
Reference:
[1] "Optimizing extended-release carbidopa/levodopa in Parkinson disease
Consensus on conversion from standard therapy"
Alberto J. Espay, MD, MSc; Fernando L. Pagan, MD; Benjamin L. Walter, MD; John C. Morgan, MD, PhD; Lawrence W. Elmer, MD, PhD; Cheryl H. Waters, MD; Pinky Agarwal, MD; Rohit Dhall, MD; William G. Ondo, MD; Kevin J. Klos, MD; Dee E. Silver, MD
Neurology Clinical Practice, 2017
http://cp.neurology.org/content/neur...00316.full.pdf
John