the present invention concerns a method for treating parkinsons &# 39 ; s disease using an oral dosage formulation comprising an immediate release layer of 10 - 25 mg of carbidopa and 50 - 200 mg of levodopa and a sustained release layer of 25 - 75 mg of carbidopa and 100 - 400 mg of levodopa whereby , following administration , carbidopa and levodopa are available for rapid and sustained therapeutic action . an oral dosage formulation in the present method can be further characterized by a sustained release core depot of carbidopa - levodopa overcoated by an immediate release layer of carbidopa - levodopa . another aspect of the orally administering the dosage comprises administering a multilayer tablet comprising at least one layer of sustained release carbidopa - levodopa adjacent to at least one layer of immediate release carbidopa - levodopa . if desired , the layers in tablet are separated by an excipient layer . another aspect of the invention therefore concerns a pharmaceutical composition in oral dosage form for treating parkinson &# 39 ; s disease , which comprises a combination of an immediate release portion of a combination of carbidopa and levodopa and a sustained release portion of a combination of carbidopa and levodopa and a pharmaceutically acceptable vehicle . the composition is effective in treating parkinson &# 39 ; s disease . the dosage form is such that carbidopa and levodopa are available for immediate and sustained therapeutic action upon administration . the pharmaceutical composition can be in a dosage form that comprises a sustained release core portion of carbidopa and levodopa overcoated by an immediate release layer of carbidopa and levodopa . the pharmaceutical composition can also be in a dosage form that comprises a multilayer tablet which comprises at lease one layer of sustained release carbidopa - levodopa adjacent to at least one layer of immediate release carbidopa - levodopa . in the pharmaceutical composition , in dosage form , an immediate release portion comprises about 10 - 25 mg of carbidopa and 50 - 200 mg of levodopa and a sustained release portion comprises about 25 - 75 mg of carbidopa and 100 - 400 mg of levodopa . the pharmaceutical composition in dosage form can comprise a sustained release core portion of carbidopa - levodopa overcoated by an immediate release layer of carbidopa - levodopa . the pharmaceutical composition in the dosage form can comprise a multilayer tablet of at least one layer of sustained release carbidopa - levodopa adjacent to at least one layer of immediate release carbidopa - levodopa . the novel oral dosage formulations of the present invention each contain immediate release and controlled release components of the antiparkinson agents carbidopa ( 5 - 200 mg ) and levodopa ( 25 - 600 mg ). the conventional immediate release combination of carbidopa - levodopa reaches peak plasma concentrations in 30 minutes whereas the onset of the controlled release component is two hours followed by prolonged release over a four - to six - hour period . the usual daily therapeutic dose of levodopa , when administered with carbidopa , is 300 to 750 mg and the dose of carbidopa approximately 75 mg per day but the latter is apparently devoid of adverse effects even at doses of 400 mg per day ( j . e . ahlskog , hosp . form ., 27 : 146 , 1992 ). although the optimum daily dosage of carbidopa - levodopa must ultimately be determined by titrating each patient , a preferred range for twice daily maintenance therapy may include immediate release of 10 - 25 mg carbidopa and 50 - 200 mg levodopa and sustained release of 25 - 75 mg carbidopa and 100 - 400 mg levodopa . specific examples of these formulations are cited below . the amount and excipients listed can be changed through methods known to those skilled in the preparation of immediate and sustained release dosage forms . some of these methods are available in remington &# 39 ; s pharmaceutical sciences , 17th ed ., 1985 , a standard reference in the field . a two compartment tablet consisting of a core layer of sustained release carbidopa - levodopa overcoated with a layer of immediate release carbidopa - levodopa . the core ingredients are blended separately ( as are the outer layer ingredients ), compressed to produce core tablets and then overcoated with the compressed outer layer blend using a suitable coating press . a bilayer or multilayer tablet consisting of one layer of sustained release carbidopa - levodopa either adjacent to a layer of immediate release carbidopa - levodopa or separated by an additional excipient layer . the ingredients from each layer are blended separately , then compressed to produce a layered tablet using a suitable layered press . an oral dosage form , such as a capsule or compressed tablet , containing immediate and sustained release carbidopa - levodopa pellets prepared by the following methods : 3 . layer the slurry from step 2 onto sugar spheres to form core pellets using a fluid - bed with a wurster air suspension coating column 4 . dissolve ethyl cellulose and polyethylene glycol 4000 in methylene chloride and methanol ( 4 : 1 ) mixture ( 5 % w / w ) 5 . coat pellets from step 3 with polymer solution from step 4 in a fluid - bed with a wurster air suspension coating column . appropriate amounts of uncoated core pellets containing immediate release carbidopa - levodopa ( step 3 ) and polymer coated pellets containing sustained release carbidopa - levodopa ( step 5 ) are included in an oral dosage form to provide the desired ratio of immediate and sustained release carbidopa - levodopa .
an oral antiparkinson drug delivery system consisting of carbidopa and levodopa in immediate and sustained release compartments provides a significant clinical advantage over currently available carbidopa - levodopa preparations .