interval in the single oral dose pharmaceutical composition of the invention a substantial portion of entacapone or a salt thereof may be separated from a mixture of levodopa and carbidopa or salts thereof or a substantial portion of carbidopa or a salt thereof may be separated from a mixture of levodopa and entacapone or salts thereof or the carbidopa entacapone or levodopa may be present simultaneously in a mixture the term u2018 substantial portion u2019 of entacapone carbidopa levodopa or a salt thereof herein refers to the amount of entacapone carbidopa levodopa or salts thereof that do not interfere with stability and or dissolution and therapeutic effect or bioavailability thereof of any of entacapone carbidopa levodopa in a single oral dose combination of entacapone levodopa and carbidopa the composition of the invention may exhibit pharmacokinetic profile characterized by maximum plasma concentration c max from about 1 1 to about 2 0 u03bcg ml time to reach maximum plasma concentration t max from about 1 6 to about 3 5 h area under the concentration time curve auc 0 t and auc 101 from about 1 80 to about 3 50 u03bcg h ml at 90 confidence interval area under the concentration time curve auc 0 t and or auc 101 values of composition of the invention may be between 0 70 and 1 30 and maximum plasma concentration c max values of composition of the invention may be between 0 60 and 1 40 as compared to that obtained.