Pharmacokinetic and clinical evaluation of liquid L-dopa/carbidopa in Parkinson's disease.

The aim of the study was to assess the pharmacokinetic properties and clinical effectiveness of L-dopa/carbidopa solution treatment in patients with parkinsonian motor fluctuations. No significant difference in maximal L-dopa concentration, time to peak L-dopa concentration and area under curve was found in single dose studies which compared equivalent tablet and solution L-dopa/carbidopa doses in 9 patients. Seven out of 10 patients treated with hourly doses of liquid L-dopa/carbidopa were improved after switching from conventional tablet medication. Less 'off' time per day and less 'off' phase disability were the usual benefits. Six of these patients maintained this improvement and continued on long-term liquid medication. The benefits of this treatment do not relate to improved L-dopa delivery to the bloodstream. The ability of patients to fractionate the treatment into small, frequent doses which can be used more flexibly than tablets appears to confer the main advantages of liquid L-dopa/carbidopa in the management of parkinsonian motor fluctuations.