The present invention relates to an extended release therapeutic drug deliverysystem comprising a controlledre-lease core matrix composition comprising an active pharmaceuticalingredient such as a central nervous system stimulant (e.g.,methylphenidate) and a release controlling agent (i.e., HPMC -K4M, HPMC-K I00MCR or HPMC-K 15 M CR) as well as acon-trolled release coating layer composition covering the core matrixcomposition, which comprises controlled release polymers suchas Eudragit RL 30D. The extended release therapeutic drug delivery system isfor use once or twice daily administration. Thepresent invention also relates to processes for manufacturing such an extendedrelease therapeutic drug delivery system.
