There are two issues with different formulations of Levodopa/Carbidopa - aside from differences between the long acting and regular versions.
1. There is quite a large leeway allowable between the formulation for generics as to branded (+/-)
2. The tablet base ingredient or carrier may be more or less soluble.
Merck recently changed the presentation of it's branded Sinemet tablets in the USA, though not apparently everywhere in the world.
There are good reasons why PD drugs should be more tightly manufactured:
1.We are sensitive to changes in dose, and a relatively small amount of the active ingredient reaches our brain. What doesn't get to our brains may be implicated in the development of dyskinesias.
2.Levodopa is absorbed in the gut and it is crucial that tablets are soluble enough to be absorbed in the right place, otherwise the dose might fail. This is especially important for older PwP who may have impaired digestion too.
I have tried without success to confront the problem of variability with a manufacturer; there needs more awareness. I had a batch of branded tablets that did not do the same as anything I had taken before, they simply did not work. Following an official complaint I was 'reassured' by the manufacturer that they could find nothing wrong with that batch. They were not interested in looking at the actual tablets I had been prescribed, yet anything could have happened between manufacture and being dispensed by my pharmacy, and in fact here in Europe many drugs cross borders several times to add market value (don't ask me how it works, I do not understand it!) often coming into the UK, being sent elsewhere, and then re-imported. There were similar problems around at the time as are being discussed on this thread! It does raise an issue of how they test for efficacy, because they sure do not test them on us
Having said the above, I don't think it is always a problem of good v bad, it is can be about what each of us is accustomed to. These are powerful drugs, and our personal adjustment to them is very fine. Changes can take a while to adjust to, sometimes weeks, and we lose quality time to manufacturing variability, something that apparently pharma is barely aware of, and seems to have little intention of tackling.
The BMS and Merck (MSD) branded tablets should be the same, but they can be different, not just in effect, but even the actual tablets. Here in the UK we are still getting oval yellow 100/25's; sometimes they are much more crumbly than other times. There is a difference between these, but when I try and put it in words that a non-PDer might understand it sounds pretty subjective. Both work, but differently. I described the bad batch as the difference between a good wine and cheap and nasty plonk! One made me feel better, and the other left me incapacitated... And therein lies the real problem........ we are the only people who know what we are talking about !
John, I have had a return of nausea after several years of none, makes a bad start to the day. No sickness though. All mine are yellow....