General Information

Duopa is an enteral suspension of carbidopa and levodopa. Carbidopa inhibits the decarboxylation of peripheral levodopa, making more levodopa available for delivery to the brain.

Duopa is specifically indicated for the treatment of motor fluctuations in patients with advanced Parkinson’s disease.

Duopa is supplied as a solution for enteral infusion. Duopa is administered over a 16-hour infusion period. The maximum recommended daily dose of Duopa is 2000 mg of levodopa (i.e., one cassette per day) administered over 16 hours. Prior to initiating Duopa, convert patients from all forms of levodopa to oral immediate-release carbidopa-levodopa tablets. Titrate total daily dose based on clinical response for the patient. Administer Duopa into the jejunum through a percutaneous endoscopic gastrostomy with jejunal tube (PEG-J). Please see drug label for specific dosing instructions.

Clinical Results

FDA Approval

The FDA approval of Duopa was based on a randomized, double-blind, double-dummy, active controlled, parallel group, 12-week study in 66 patients with advanced Parkinson's disease who were levodopa-responsive and had persistent motor fluctuations while on treatment with oral immediate-release carbidopa-levodopa and other Parkinson's disease medications. Patients were eligible for participation in the studies if they were experiencing 3 hours or more of “Off” time on their current Parkinson's disease drug treatment and they demonstrated a clear responsiveness to treatment with levodopa. Patients were randomized to either Duopa and placebo capsules or placebo suspension and immediate-release carbidopa-levodopa 25/100 mg capsules. Patients in both treatment arms had a PEG-J device placement. Duopa or placebo-suspension was infused over 16 hours daily. The mean daily levodopa dose was 1117 mg/day in the Duopa group and 1351 mg/day in the oral immediate-release carbidopa-levodopa group. The clinical outcome measure in Study 1 was the mean change from baseline to Week 12 in the total daily mean “Off” time, based on a Parkinson's disease diary. The "Off" time was normalized to a 16-hour awake period. The mean score decrease (i.e., improvement) in “Off” time from baseline to Week 12 for Duopa was significantly greater (p=0.0015) than for oral immediate release carbidopa-levodopa. Additionally, the mean score increase (i.e., improvement) in “On” time without troublesome dyskinesia from baseline to Week 12 was significantly greater (p=0.0059) for Duopa than for oral immediate-release carbidopa-levodopa. The treatment difference (Duopa – oral immediate release carbidopa-levodopa) for decrease in “Off” time was approximately 1.9 hours and the treatment difference for the increase in “On” time without troublesome dyskinesia was approximately 1.9 hours.

Mechanism of Action

Duopa is an enteral suspension of carbidopa and levodopa. Carbidopa: When levodopa is administered orally, it is rapidly decarboxylated to dopamine in extracerebral tissues so that only a small portion of a given dose is transported unchanged to the central nervous system. Carbidopa inhibits the decarboxylation of peripheral levodopa, making more levodopa available for delivery to the brain. Levodopa: Levodopa is the metabolic precursor of dopamine, does cross the blood-brain barrier, and presumably is converted to dopamine in the brain. This is thought to be the mechanism whereby levodopa treats the symptoms of Parkinson's disease.