Efficacy, Safety, and Pharmacokinetics/Pharmacodynamic Study of L-Dopa/Carbidopa To Treat Parkinson's Disease

Inclusion Criteria: * Clinical diagnostic of Parkinson's Disease, with a Hoehn and Yahr Staging within 2-4, and L-Dopa therapy complications * at least 2years of L-Dopa therapy * Patients with the ability to differentiate between "ON" and "OFF" periods * Patients who have been receiving stable doses of L-Dopa between 600 and 1600 mg/day, for at least 2 months prior to the screening visit using a dosing regimen not higher that 5 times a day, and not expected in the investigator's opinion to need any dose modifications over the duration of the study * Patients presenting a score of at least 2 in the UPDRS IVa, item 32 and/or a score of at least 2 in the UPDRS IVb, item 39, at screening and randomization visits based on clinical records for the first visit and daily diary cards at randomization time. * Willing and able to understand and sign Informed Consent form Exclusion Criteria: * Patients with a diagnosis of any known secondary Parkinsonian syndrome, (vascular, toxin or drug-induced, metabolic or infectious, etc) or other neurodegenerative disorder with parkinsonism (Progressive Supranuclear Palsy, Corticobasal Degeneration, Multiple System Atrophy, etc). * Patients receiving other concomitant anti-Parkinsonian pharmacological therapies affecting L-dopa or dopamine metabolisom (COMT inhibitors or MAO inhibitors) * Subjects who have undergone prior functional neurosurgical treatment for PD (ablation or Deep Brain Stimulation). * Patient with a L-dopa dosage regimen greater than 5 times a day which is not able to be adapted to a q.i.d. regimen. * Patients having received L-dopa / Decarboxylase inhibitors therapy for less than 2 years. * Patients needing nightly doses of L-dopa / Decarboxylase inhibitors apart from the four daily doses. * Any medical condition or past medical history that, in the investigator's judgment, would increase the risk of exposure to L-dopa / Carbidopa or interfere with the evaluation of the study objectives. * Patients with unstable or clinically significant known medical illness; such as cardiac, pulmonary, kidney, hepatic and/or gastrointestinal disease that would, in the investigator's judgment, interfere with the safe course of the study. * Cognitive impaired patients, as determined by a score of lesser than 26 on the Mini-Mental Score Status Examination. (MMSE \< 26). * Alcohol or illegal drugs abuse. * Pregnant or lactating patients. * Hypersensitivity to any of the investigational drugs, based on known allergies to drugs of the same class. * Patients having taken any research drugs over the last 30 days prior to the beginning of the study. * Blood donation, or blood products, or participation to a clinical trial with serial blood withdrawals, within twelve weeks prior to the start of the trial, or intention to donate blood or blood products within three months following the study completion. * Patients who have received some of the following medications with an anticipation of no more than 7 treatment-drug elimination half-lives of entry time: Dopamine D2 receptor antagonists , isoniazid, anti-epileptic drugs, IMAO A or B, pyridoxine, ferrous salts or methyldopa.