The present invention relates to pharmaceutical formulations for the controlled delivery of threo-3-(3,4-dihydroxyphenyl)serine (threo-DOPS) and derivatives of it. Such formulations can contain an extended or slow release component that maintains therapeutic concentration of threo-DOPS in the blood plasma over a prolonged time period. They can be further combined with an immediate release formulation to produce a product that, when administered to a patient in need thereof, results in substantially steady levels of active drug, eliminating the sharp peaks and troughs in blood plasma drug levels experienced with the existing threo-DOPS formulations.
