Ah, at last someone who is also curious about Carbidopa. This is usually overlooked, but apart from its role in Sinemet of protecting the levodopa from breaking down prematurely, it must have its own lot of side effects, but rarely gets a mention. The total daily amount is what is important apparently, 70 mg is the minimum amount that is required to really make the levodopa along, So 3 x 125 mg Sinemet is the considered effective starting dose, as it gives you 75mg of carbidopa a day,. Even so, I took 3 x 62,5mg (12,5 mg carbidopa per tablet) Sinemet for a t least a year with good results, but theoretically it should not work so well.) I had great difficulty explaining to the Parkinson nurse that if there was a minimum, there is most likely a max dose too. and that I was concerned that in the course of the disease you would reach this level. Moreover it was clear the manufacturers thought along the same lines and there is besides the 12,5/50 and the 25/100 (or the 1:4 , i.e. carbidopa/ levodopa proportions) there is a 1:10 version. Apparently the FDA advises in the USA that 200mg Carbidopa is the recommended max.daily dose. Some later research that was done to look into the possible harm higher doses could do, found no reason to set a ceiling of 200mg,.