Fluctuations in plasma levodopa and motor responses with liquid and tablet levodopa/carbidopa

To evaluate the ability of orally administered liquid levodopa/carbidopa (LD/CD) to stabilize plasma levodopa levels and reduce motor response fluctuations in Parkinson's disease, five patients received LD/CD hourly, as standard tablets or as an aqueous solution on two separate days in a double-blind, placebo-controlled, cross-over design. Except for a slightly earlier peak plasma levodopa level, no significant advantage of the liquid formulation over tablet therapy was found. However, liquid LD/CD could be helpful in quickly resolving "off" states and by facilitating small dose adjustments that are not possible with tablets.