A novel matrix composition for pharmaceutical use. The matrix composition has been designed so that it is especially suitable in those situation where an improved bioavailability is desired and/or in those situation where a slightly or insoluble active substance is employed. Accordingly, a controlled release pharmaceutical composition for oral use is provided in the form of a coated matrix composition, the matrix composition comprising i) a mixture of a first and a second polymer that have plasticizing properties and which have melting points or melting intervals of a temperature of at the most 200 °C, the first polymer being selected from the group consisting of polyethylene glycols and polyethylene oxides having a molecular weight of at least about 20,000 in crystalline and/or amorphous form or a mixture such polymers, and the second polymer being selected from block copolymer of ethylene oxide and propylene oxide including poly(ethylene-glycol-b-(DL-lactic acid-co-glycolic acid) - b- ethylene glycol (PEG-PLGA PEG), poly((DL-lactic acid-co-glycolic acid) - g-ethylene glycol) (PLGA-g-PEG), poloxamers and polyethylene oxide - polypropylene oxide (PEO-PPO), ii) a therapeutically, prophylactically and/or diagnostically active substance, wherein the concentration of the second polymer in the matrix composition is from about 5 to about 90% w/w, the matrix composition being provided with a coating having at least one opening exposing at one surface of said matrix, the coating comprising i) a first cellulose derivative which has thermoplastic properties and which is substantially insoluble in the aqueous medium in which the composition is to be used, and at least one of ii) a second cellulose derivative which is soluble or dispersible in water, iii) a plasticizer, and iv) a filler, wherein the active substance is released with a substantially zero order release.
