no, it doesn't negate the ER function, if it did the tablet wouldn't be scored, the package insert states it can be halved but not quartered. if you chew a ER then it approximates 200mg of LDOPA and 50mg of carbidopa. the C/L is mixed up in a matrix of starches, cellulose, maybe wax, so the matrix is maintained when split.

with ER, because it stays in your stomach longer, more of the l-dopa is broken down so it is estimated to be 60-80% bioavailable when compared to regular l-dopa.. i use the 60% number when calculating the total l-dopa i take/day, so a whole CR=120mg regular l-dopa.

btw, i prefer the mylan brand which i guess isn't available due to hurricane damage in puerto rico.