This study is a double-blind, randomized, placebo-controlled, 2-way crossover study to evaluate the safety of CVT-301 levodopa (l-dopa) when co- administered with the first daily dose of oral levodopa/carbidopa for early morning OFF symptoms in patients with Parkinson's disease (PD).

An "OFF state" is defined as the time when medication is no longer providing benefit with respect to mobility, slowness, and stiffness. OFF episodes may be heralded by non-motor symptoms (e.g., pain, anxiety) prior to the appearance of motor symptoms.

Inclusion Criteria:

• have idiopathic PD (i.e., not induced by drugs or other diseases) as defined by fulfilling Steps 1 and 2 of the United Kingdom (UK) Brain Bank criteria, diagnosed after the age of 30 years
• diagnosis of Parkinson's disease and motor fluctuations and early morning OFF symptoms
• classified as Stage 1 to 3 on the modified Hoehn and Yahr scale for staging of PD severity (in an ON state)
• subjects who are on a l-dopa-containing therapy, not including Rytary (or equivalent), must be stable on oral l-dopa-containing therapy for at least 2 weeks prior to the Screening Visit with a l-dopa/decarboxylase inhibitor (DDI)-containing regimen
• subjects who are on a l-dopa-containing therapy, when including Rytary (or equivalent), should be on a stable dose for at least 6 weeks prior to the Screening Visit
• the frequency of l-dopa administrations must be at least 3 times during the waking day and a total daily l-dopa dose of ≤ 1600 mg.
• on a stable regimen of their standard PD medications
• on a stable regimen of any blood pressure reducing medications (if applicable) for at least 30 days prior to screening
• forced expiratory volume in one second (FEV1) ≥60% of predicted for race, age, sex, and height and FEV1/FVC (forced vital capacity) ratio ≥70%
• no clinically significant abnormalities that would affect ability to complete study as determined by medical history, physical examination, electrocardiogram, clinical laboratory test results
• negative drug and alcohol testing
• negative pregnancy test for all women.

Exclusion Criteria:

• participated in any prior study with CVT-301
• dyskinesia of a severity that would significantly interfere with the subject's ability to participate or perform study procedures (as determined by the UPDRS Part 4)
• any contraindication to performing routine spirometry or who are unable to perform a spirometry maneuver
• have a current history of symptomatic orthostatic hypotension or are treated with medications to treat orthostatic hypotension (for example droxidopa, fludrocortisone), if they have severe dysautonomia
• have chronic obstructive pulmonary disease (COPD), asthma, or another chronic respiratory disease within the last 5 years.