Can anyone tell me why sometimes 100mg/10 mg levodopa/carbidopa is used instead of standard 100/25 version

[Connie18]

Sinemet 100/10

[johntPM]

If levodopa is taken on its own, most of it would be metabolized before it got to the brain, where it can start to do good. Carbidopa reduces the amount of levodopa that is lost. However, there are diminishing returns as the ratio of carbidopa increases. This is especially true of people on high doses of levodopa. The maximum dose per day of carbidopa is 200 mg. With the now normal ratio of levodopa/carbidopa of 4:1, the maximum is reached with a daily dose of 800 mg of levodopa. Any extra dose, could be of the 10:1 variant. In the ideal world the levodopa and the carbidopa would be taken separately in order to match individual needs.

[eschneid in reply to johntPM]

John,

Expand a b i t on Carbidopa maximum being 200 mg per day if you don't mind. I was not aware of that number.

[johntPM in reply to eschneid]

eschneid,

Thank you for raising the issue.

Brod, Aldred and Nutt [1] write:

"FDA approved drug information indicates that the daily dose of carbidopa should not exceed 200 mg because there is inadequate experience with higher doses."

However, on the basis of a small trial, n=12, they go on to write:

"Doses of 450 mg/day of carbidopa did not reduce the responses to levodopa infusion, extending the safe range of carbidopa to 450 mg/day."

Can anyone find a more recent or larger trial?

Reference:

[1] "Are high doses of carbidopa a concern? A randomized clinical trial in Parkinson’s disease"

Mov Disord 2012

Lissa S. Brod, MD, Jason L. Aldred, MD, and John G. Nutt, MD

ncbi.nlm.nih.gov/pmc/articl...

John

[eschneid in reply to johntPM]

Thx John

[WinnieThePoo]

10/100 delivers less levadopa to the brain than 25/100. It enables fine tuning of the levadopa dose where this is thought to be important

[Esperanto]

Can we assume that the efficacy of 10/100 is roughly equivalent to half a 25/100? Does anyone know the link to a study of the efficacy of the high and low carbidopa versions? Possibly a nice graph would also be helpful on the influence of carbidopa on the action of levodopa in general. In addition, I think the longer-term impact of both verslons would also be interesting to know. Merci in advance 🍀

[Esperanto in reply to Esperanto]

No, that was a fallacy. Although after about 3 hours after ingestion this will be about the case due to the short half-life of levodopa without carbidopa. However, the first 2 hours after taking levodopa, the difference with or without carbidopa addition is relatively much less. Earlier today I showed a partly estimated Pharmacokinetics, pharmacodynamics chart of the different C/L IR medications.

healthunlocked.com/cure-par...

It would be much better if I could still find the graphs with measured research results, 🍀