The purpose of this study is to determine the long-term efficacy and safety of two doses of safinamide (50 and 100 mg/day, p.o), compared to placebo, as add-on therapy in patients with idiopathic Parkinson's disease with motor fluctuations, who are currently receiving a stable dose of levodopa.

Inclusion Criteria:

• The patient completed 24 weeks of treatment in Study 016, or, if the patient discontinued prematurely, he/she returned for scheduled efficacy evaluations at Weeks 12 and 24, as part of the Retrieved Dropout (RDO) population.
• The patient was compliant with taking study medication in Study 016.
• The patient is willing to participate in the study and signed an approved Informed Consent form.

Exclusion Criteria:

• The patient is experiencing clinically significant adverse events that would put the patient at risk for participating in the study.
• The patient has shown clinically significant deterioration during participation in Study 016, and has reached Hoehn and Yahr Stage V.
• The patient discontinued Study 016 prematurely for any reason, and did not return for scheduled efficacy evaluations at Weeks 12 and 24.