Long-term clinical efficacy of Sinemet CR in patients with Parkinson's disease.

Sinemet CR, a controlled-release form of carbidopa/levodopa, was administered for 36 or 39 months to 8 patients with Parkinson's disease in an open-label study. On standard Sinemet each patient had experienced "wearing off" phenomena, and 5 had also experienced random "off" episodes. Daily "on" time, dyskinesia time, disability score, levodopa dosage requirement, and dosing frequency on Sinemet CR were compared with baseline values on standard Sinemet therapy. After both 3 and 36 or 39 months of Sinemet CR therapy, 5 patients showed increased daily "on" time compared with baseline. All 8 required fewer daily doses after 3 months on Sinemet CR, but only 3 were still taking fewer doses after 36 or 39 months. Disability scores remained essentially unchanged. Patients continued to elect to remain on Sinemet CR over the 3-year period, citing improved predictability of response and less severe and precipitous "off" episodes as the main reasons. This experience suggests that patient acceptance of Sinemet CR remains high. A modest improvement in "on" time can be achieved and maintained in some patients for as long as 3 years. However, as with standard Sinemet, dosing frequency for Sinemet CR may need to be gradually increased with time in order to maintain benefits achieved.