Parkinsons - Is it true that the bioequivalent dose of Sinement CR is 75-80% of the regular Sinemet (carbidopa and levodopa)?

Answer varies. The bioequivalent dose actually depends on the dose that is needed, your metabolism, what other medicines you use, an your experience with these medicines. The ratio of sinemet (carbidopa and levodopa) CR to regular sinemet (carbidopa and levodopa) may vary from 50% to 100% of the regular dose. Your number (75%) is right inbetween. For 600 mg regular sinemet (carbidopa and levodopa), most would start with 300 mg sinemet (carbidopa and levodopa) CR.