Controlled-release carbidopa/levodopa (CR) in parkinsonian patients with response fluctuations on standard levodopa treatment: clinical and pharmacokinetic observations.

The efficacy of an oral controlled-release preparation of carbidopa/levodopa (Sinemet CR 50/200 mg) was compared with conventional carbidopa/levodopa (25/250 mg) in an open-label study. Twenty patients with idiopathic Parkinson's disease and severe response fluctuations participated. At the end of 6 months of CR treatment, the major clinical benefits included improvement of disability, reduction in number of "off" periods (predominantly end-of-dose hypokinesia), and increase in percentage of "on" time. Although dosages of CR required for an optimal therapeutic response were not significantly higher compared with conventional levodopa, bioavailability significantly increased. Delayed onset of antiparkinsonian effect of CR, resulting from an increase of Tmax for levodopa, was one of the major patient complaints and required additional small amounts of standard levodopa in some patients.