Controlled-release levodopa/carbidopa. II. Sinemet CR4 treatment of response fluctuations in Parkinson's disease.

Sixteen patients with Parkinson's disease and therapeutic response fluctuations entered an open-label trial of a controlled-release carbidopa/levodopa preparation, Sinemet CR4. Sinemet CR4 behaved as a slow release preparation. At the end of 6 weeks CR4 treatment, there was an increase in percent "on" time and mean interdose interval; the number of daily doses and "off" periods were diminished and a slight reduction in the variability of plasma levodopa levels was observed. Overall benefit waned over the next 6 months, despite addition of standard levodopa or Sinemet to overcome the delayed onset of antiparkinsonian effect of CR4 which resulted from prolongation in the Tmax for levodopa. The major benefits of CR4 were reduction in off time and in the number of daily off periods, with fewer levodopa doses per day and prolongation of the interdose interval.