As I understand it, the benefits of Duodopa come from the ability to reduce plasma variability of levodopa, rather than from any chemical differences. [1] states:
"1 ml [of Duodopa] contains 20 mg levodopa and 5 mg carbidopa monohydrate"

The issue here is can we make better use of present medications. Do we take into account the effects of diet (protein intake especially) and gastric emptying rates? Do we know the effect of reducing the time between oral doses?

There is also the possibility that some of the apparent marginal (as compared to standard levodopa preparations) benefit comes from an increased total daily dose. An indication of the doses involved is given by [1].

"The average recommended daily dose of Duodopa is 100 ml, containing 2 g levodopa and 0.5 g carbidopa".

Note: that's 2g = 2000mg

The issue here is would many people with advanced Parkinson's benefit from increased doses of levodopa?

References

[1] eMC
http://www.medicines.org.uk/emcmobil...cine/20786/spc

John