Carbidopa/Levodopa extended release capsules in patients with Parkinson’s disease with and without dyskinesia: a comparison

This study compared carbidopa–levodopa (CL) extended-release (ER) with immediate-release (IR) in patients with Parkinson's disease (PD) and dyskinesia (dys). Researchers suggested that conversion from CL-ER to CL-IR works best in patients without dys or with minor dys.

PD affects certain brain cells. These cells lose their abilities in controlling the body functions causing symptoms such as tremors and stiffness. The standard treatment is levodopa alone or CL combinations. 

Long-term use of CL-IR (Sinemet) was associated with negative side effects such as dys or OFF periods. Dys consists of uncontrolled, involuntary movements. OFF periods involve the return of PD symptoms usually before the next dose of CL. The CL-ER (Rytary) formulation helps to maintain more stable levels of CL between doses, decreasing the chances of OFF times compared to CL-IR. However, the effectiveness of this treatment is not clear in patients with different dys status.

This study included information about 393 patients with different dys status. Of these, 183 had no dys (group 1), 131 had non-troublesome dys (group 2) and 79 had troublesome dys (group 3). All patients were taking CL-IR before the study. Half of the patients in each group were switched to CL-ER and half remained on CL-IR. 

CL-ER was significantly associated with reductions in OFF time in groups 1 and 2. Group 3 had a smaller reduction in OFF times with CL-ER. Patients from group 1 on CL-ER had a 2.86 hours reduction in OFF time, comparing to a 1.78 hours reduction in CL-IR-treated patients. In group 2, patients treated with CL-ER had a 2.11 hours reduction of OFF time, while CL-IR-treated patients had a 0.99 hours reduction. In group 3, CL-ER patients had a 1.36 hours reduction in OFF times, while CL-IR-treated patients had a 0.55 hours reduction. 

Groups 1 and 2 had similar rates of side effects for CL-ER and CL-IR. However, in patients from group 2, those treated with CL-ER had side effects more commonly than those treated with CL-IR (50% vs 37.1%). The most common side effects in this group was falls (9.1% for CL-ER vs 2.9% for CL-IR).

This study concluded that treatment response to CL-ER is higher in patients without troublesome dys.

This study was based on medical records. Some information might have been incomplete. This might affect the results. Also, this study was funded by Amneal Pharmaceuticals, the manufacturer of CL-ER.