Disclosed herein are stable pharmaceutical dosage forms containing carbidopa, levodopa, and entacapone. The dosage forms are prepared by mixing carbidopa, levodopa, and entacapone and forming granules. In some embodiments the granules also include starch. Microcrystalline cellulose can be added as an extragranular excipient. The stable pharmaceutical dosage forms have a bioavailability that is substantially similar to a dosage form prepared by adding a substantial portion of carbidopa separately from levodopa and entacapone.
